[ci] Reduce non-deterministic builds for eslint-plugin-react-hooks

See https://github.com/rollup/plugins/issues/1425

Currently, `@babel/helper-string-parser/lib/index.js` is either emitted as a wrapped esmodule or inline depending on the ordering of async functions in `rollup/commonjs`. Specifically, `@babel/types/lib/definitions/core.js` is cyclic (i.e. transitively depends upon itself), but sometimes `@babel/helper-string-parser/lib/index.js` is emitted before this is realized.


A relatively straightforward patch is to wrap all modules (see https://github.com/rollup/plugins/issues/1425#issuecomment-1465626736)

.codesandbox/ci.json

@@ -1,10 +1,11 @@
 {
-  "packages": ["packages/react", "packages/react-dom", "packages/scheduler"],
+  "packages": ["packages/react", "packages/react-dom", "packages/react-server-dom-webpack", "packages/scheduler"],
   "buildCommand": "download-build-in-codesandbox-ci",
   "node": "18",
   "publishDirectory": {
     "react": "build/oss-experimental/react",
     "react-dom": "build/oss-experimental/react-dom",
+    "react-server-dom-webpack": "build/oss-experimental/react-server-dom-webpack",
     "scheduler": "build/oss-experimental/scheduler"
   },
   "sandboxes": ["new"],

.eslintrc.js

@@ -615,6 +615,8 @@ module.exports = {
     GetAnimationsOptions: 'readonly',
     Animatable: 'readonly',
     ScrollTimeline: 'readonly',
+    EventListenerOptionsOrUseCapture: 'readonly',
+    FocusOptions: 'readonly',
 
     spyOnDev: 'readonly',
     spyOnDevAndProd: 'readonly',

.github/ISSUE_TEMPLATE/19.md

@@ -1,18 +0,0 @@
----
-name: "⚛React 19 beta issue"
-about: Report a issue with React 19 beta.
-title: '[React 19]'
-labels: 'React 19'
-
----
-
-
-## Summary
-
-<!--
-  Please provide a CodeSandbox (https://codesandbox.io/s/new), a link to a
-  repository on GitHub, or provide a minimal code example that reproduces the
-  problem. You may provide a screenshot of the application if you think it is
-  relevant to your bug report. Here are some tips for providing a minimal
-  example: https://stackoverflow.com/help/mcve.
--->

.github/workflows/compiler_discord_notify.yml

@@ -1,7 +1,7 @@
 name: (Compiler) Discord Notify
 
 on:
-  pull_request:
+  pull_request_target:
     types: [opened, ready_for_review]
     paths:
       - compiler/**
@@ -10,7 +10,19 @@ on:
 permissions: {}
 
 jobs:
+  check_access:
+    runs-on: ubuntu-latest
+    outputs:
+      is_member_or_collaborator: ${{ steps.check_is_member_or_collaborator.outputs.is_member_or_collaborator }}
+    steps:
+      - name: Check is member or collaborator
+        id: check_is_member_or_collaborator
+        if: ${{ github.event.pull_request.author_association == 'MEMBER' || github.event.pull_request.author_association == 'COLLABORATOR' }}
+        run: echo "is_member_or_collaborator=true" >> "$GITHUB_OUTPUT"
+
   check_maintainer:
+    if: ${{ needs.check_access.outputs.is_member_or_collaborator == 'true' || needs.check_access.outputs.is_member_or_collaborator == true }}
+    needs: [check_access]
     uses: facebook/react/.github/workflows/shared_check_maintainer.yml@main
     permissions:
       # Used by check_maintainer

.github/workflows/compiler_playground.yml

@@ -40,8 +40,12 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
+          key: compiler-and-playground-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+        working-directory: compiler
+      - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Check Playwright version
         id: playwright_version
         run: echo "playwright_version=$(npm ls @playwright/test | grep @playwright | sed 's/.*@//' | head -1)" >> "$GITHUB_OUTPUT"

.github/workflows/compiler_prereleases.yml

@@ -16,6 +16,9 @@ on:
       version_name:
         required: true
         type: string
+      tag_version:
+        required: false
+        type: string
     secrets:
       NPM_TOKEN:
         required: true
@@ -49,9 +52,10 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
+          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Publish packages to npm
         run: |
           cp ./scripts/release/ci-npmrc ~/.npmrc
-          scripts/release/publish.js --frfr --ci --versionName=${{ inputs.version_name }} --tag ${{ inputs.dist_tag }}
+          scripts/release/publish.js --frfr --ci --versionName=${{ inputs.version_name }} --tag=${{ inputs.dist_tag }} ${{ inputs.tag_version && format('--tagVersion={0}', inputs.tag_version) || '' }}

.github/workflows/compiler_prereleases_manual.yml

@@ -14,6 +14,9 @@ on:
       version_name:
         required: true
         type: string
+      tag_version:
+        required: false
+        type: string
 
 permissions: {}
 
@@ -29,5 +32,6 @@ jobs:
       release_channel: ${{ inputs.release_channel }}
       dist_tag: ${{ inputs.dist_tag }}
       version_name: ${{ inputs.version_name }}
+      tag_version: ${{ inputs.tag_version }}
     secrets:
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}

.github/workflows/compiler_prereleases_weekly.yml

@@ -1,23 +0,0 @@
-name: (Compiler) Publish Prereleases Weekly
-
-on:
-  schedule:
-    # At 10 minutes past 9:00 on Mon
-    - cron: 10 9 * * 1
-
-permissions: {}
-
-env:
-  TZ: /usr/share/zoneinfo/America/Los_Angeles
-
-jobs:
-  publish_prerelease_beta:
-    name: Publish to beta channel
-    uses: facebook/react/.github/workflows/compiler_prereleases.yml@main
-    with:
-      commit_sha: ${{ github.sha }}
-      release_channel: beta
-      dist_tag: beta
-      version_name: '19.0.0'
-    secrets:
-      NPM_TOKEN: ${{ secrets.NPM_TOKEN }}

.github/workflows/compiler_typescript.yml

@@ -47,11 +47,13 @@ jobs:
           cache-dependency-path: compiler/yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
-          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
+          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn workspace babel-plugin-react-compiler lint
 
   # Hardcoded to improve parallelism
@@ -71,8 +73,9 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
+          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn workspace babel-plugin-react-compiler jest
 
   test:
@@ -96,8 +99,9 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
+          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: xvfb-run -a yarn workspace ${{ matrix.workspace_name }} test
         if: runner.os == 'Linux' && matrix.workspace_name == 'react-forgive'
       - run: yarn workspace ${{ matrix.workspace_name }} test

.github/workflows/devtools_regression_tests.yml

@@ -40,7 +40,9 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd scripts/release install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Download react-devtools artifacts for base revision
         run: |
           git fetch origin main
@@ -75,6 +77,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Restore archived build
         uses: actions/download-artifact@v4
         with:
@@ -134,6 +137,7 @@ jobs:
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Restore all archived build artifacts
         uses: actions/download-artifact@v4
       - name: Display structure of build
@@ -169,14 +173,24 @@ jobs:
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Restore all archived build artifacts
         uses: actions/download-artifact@v4
       - name: Display structure of build
         run: ls -R build
-      - name: Playwright install deps
-        run: |
-          npx playwright install
-          sudo npx playwright install-deps
+      - name: Check Playwright version
+        id: playwright_version
+        run: echo "playwright_version=$(npm ls @playwright/test | grep @playwright | sed 's/.*@//' | head -1)" >> "$GITHUB_OUTPUT"
+      - name: Cache Playwright Browsers for version ${{ steps.playwright_version.outputs.playwright_version }}
+        id: cache_playwright_browsers
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/ms-playwright
+          key: playwright-browsers-v6-${{ runner.arch }}-${{ runner.os }}-${{ steps.playwright_version.outputs.playwright_version }}
+      - run: npx playwright install --with-deps
+        if: steps.cache_playwright_browsers.outputs.cache-hit != 'true'
+      - run: npx playwright install-deps
+        if: steps.cache_playwright_browsers.outputs.cache-hit == 'true'
       - run: ./scripts/ci/download_devtools_regression_build.js ${{ matrix.version }}
       - run: ls -R build-regression
       - run: ./scripts/ci/run_devtools_e2e_tests.js ${{ matrix.version }}

.github/workflows/runtime_build_and_test.yml

@@ -426,6 +426,10 @@ jobs:
   process_artifacts_combined:
     name: Process artifacts combined
     needs: [build_and_lint, runtime_node_modules_cache]
+    permissions:
+      # https://github.com/actions/attest-build-provenance
+      id-token: write
+      attestations: write
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -468,6 +472,7 @@ jobs:
         # TODO: Migrate scripts to use `build` directory instead of `build2`
       - run: cp ./build.tgz ./build2.tgz
       - name: Archive build artifacts
+        id: upload_artifacts_combined
         uses: actions/upload-artifact@v4
         with:
           name: artifacts_combined
@@ -475,6 +480,17 @@ jobs:
             ./build.tgz
             ./build2.tgz
           if-no-files-found: error
+      - uses: actions/attest-build-provenance@v2
+        # We don't verify builds generated from pull requests not originating from facebook/react.
+        # However, if the PR lands, the run on `main` will generate the attestation which can then
+        # be used to download a build via scripts/release/download-experimental-build.js.
+        #
+        # Note that this means that scripts/release/download-experimental-build.js must be run with
+        # --no-verify when downloading a build from a fork.
+        if: github.event_name == 'push' && github.ref_name == 'main' || github.event.pull_request.head.repo.full_name == github.repository
+        with:
+          subject-name: artifacts_combined.zip
+          subject-digest: sha256:${{ steps.upload_artifacts_combined.outputs.artifact-digest }}
 
   check_error_codes:
     name: Search build artifacts for unminified errors
@@ -797,14 +813,18 @@ jobs:
       - run: yarn --cwd scripts/release install --frozen-lockfile
         if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Download artifacts for base revision
+        # The build could have been generated from a fork, so we must download the build without
+        # any verification. This is safe since we only use this for sizebot calculation and the
+        # unverified artifact is not used. Additionally this workflow runs in the pull_request
+        # trigger so only restricted permissions are available.
         run: |
-          GH_TOKEN=${{ github.token }} scripts/release/download-experimental-build.js --commit=$(git rev-parse ${{ github.event.pull_request.base.sha }})
+          GH_TOKEN=${{ github.token }} scripts/release/download-experimental-build.js --commit=$(git rev-parse ${{ github.event.pull_request.base.sha }}) ${{ (github.event.pull_request.head.repo.full_name != github.repository && '--noVerify') || ''}}
           mv ./build ./base-build
-      # TODO: The `download-experimental-build` script copies the npm
-      # packages into the `node_modules` directory. This is a historical
-      # quirk of how the release script works. Let's pretend they
-      # don't exist.
       - name: Delete extraneous files
+        # TODO: The `download-experimental-build` script copies the npm
+        # packages into the `node_modules` directory. This is a historical
+        # quirk of how the release script works. Let's pretend they
+        # don't exist.
         run: rm -rf ./base-build/node_modules
       - name: Display structure of base-build from origin/main
         run: ls -R base-build

.github/workflows/runtime_discord_notify.yml

@@ -1,7 +1,7 @@
 name: (Runtime) Discord Notify
 
 on:
-  pull_request:
+  pull_request_target:
     types: [opened, ready_for_review]
     paths-ignore:
       - compiler/**
@@ -10,7 +10,19 @@ on:
 permissions: {}
 
 jobs:
+  check_access:
+    runs-on: ubuntu-latest
+    outputs:
+      is_member_or_collaborator: ${{ steps.check_is_member_or_collaborator.outputs.is_member_or_collaborator }}
+    steps:
+      - name: Check is member or collaborator
+        id: check_is_member_or_collaborator
+        if: ${{ github.event.pull_request.author_association == 'MEMBER' || github.event.pull_request.author_association == 'COLLABORATOR' }}
+        run: echo "is_member_or_collaborator=true" >> "$GITHUB_OUTPUT"
+
   check_maintainer:
+    if: ${{ needs.check_access.outputs.is_member_or_collaborator == 'true' || needs.check_access.outputs.is_member_or_collaborator == true }}
+    needs: [check_access]
     uses: facebook/react/.github/workflows/shared_check_maintainer.yml@main
     permissions:
       # Used by check_maintainer

.github/workflows/runtime_eslint_plugin_e2e.yml

@@ -46,17 +46,20 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: runtime-and-compiler-eslint_e2e-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock') }}
+          key: runtime-and-compiler-eslint_e2e-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock', 'fixtures/eslint-v*/yarn.lock') }}
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd compiler install --frozen-lockfile
-      - name: Build plugin
-        working-directory: fixtures/eslint-v${{ matrix.eslint_major }}
-        run: node build.mjs
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Install fixture dependencies
         working-directory: ./fixtures/eslint-v${{ matrix.eslint_major }}
         run: yarn --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - name: Build plugin
+        working-directory: fixtures/eslint-v${{ matrix.eslint_major }}
+        run: node build.mjs
       - name: Run lint test
         working-directory: ./fixtures/eslint-v${{ matrix.eslint_major }}
         run: yarn lint

.github/workflows/runtime_prereleases.yml

@@ -13,7 +13,16 @@ on:
       dist_tag:
         required: true
         type: string
+      enableFailureNotification:
+        description: 'Whether to notify the team on Discord when the release fails. Useful if this workflow is called from an automation.'
+        required: false
+        type: boolean
     secrets:
+      DISCORD_WEBHOOK_URL:
+        description: 'Discord webhook URL to notify on failure. Only required if enableFailureNotification is true.'
+        required: false
+      GH_TOKEN:
+        required: true
       NPM_TOKEN:
         required: true
 
@@ -29,6 +38,9 @@ jobs:
   publish_prerelease:
     name: Publish prelease (${{ inputs.release_channel }}) ${{ inputs.commit_sha }} @${{ inputs.dist_tag }}
     runs-on: ubuntu-latest
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
@@ -46,8 +58,18 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd scripts/release install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: |
-          scripts/release/prepare-release-from-ci.js --skipTests -r ${{ inputs.release_channel }} --commit=${{ inputs.commit_sha }}
+          GH_TOKEN=${{ secrets.GH_TOKEN }} scripts/release/prepare-release-from-ci.js --skipTests -r ${{ inputs.release_channel }} --commit=${{ inputs.commit_sha }}
           cp ./scripts/release/ci-npmrc ~/.npmrc
           scripts/release/publish.js --ci --tags ${{ inputs.dist_tag }}
+      - name: Notify Discord on failure
+        if: failure() && inputs.enableFailureNotification == true
+        uses: tsickert/discord-webhook@86dc739f3f165f16dadc5666051c367efa1692f4
+        with:
+          webhook-url: ${{ secrets.DISCORD_WEBHOOK_URL }}
+          embed-author-name: "GitHub Actions"
+          embed-title: 'Publish of $${{ inputs.release_channel }} release failed'
+          embed-url: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}/attempts/${{ github.run_attempt }}

.github/workflows/runtime_prereleases_manual.yml

@@ -16,6 +16,9 @@ jobs:
   publish_prerelease_canary:
     name: Publish to Canary channel
     uses: facebook/react/.github/workflows/runtime_prereleases.yml@main
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     with:
       commit_sha: ${{ inputs.prerelease_commit_sha }}
       release_channel: stable
@@ -32,10 +35,14 @@ jobs:
       dist_tag: canary,next
     secrets:
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
   publish_prerelease_experimental:
     name: Publish to Experimental channel
     uses: facebook/react/.github/workflows/runtime_prereleases.yml@main
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     # NOTE: Intentionally running these jobs sequentially because npm
     # will sometimes fail if you try to concurrently publish two
     # different versions of the same package, even if they use different
@@ -47,3 +54,4 @@ jobs:
       dist_tag: experimental
     secrets:
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/runtime_prereleases_nightly.yml

@@ -14,16 +14,25 @@ jobs:
   publish_prerelease_canary:
     name: Publish to Canary channel
     uses: facebook/react/.github/workflows/runtime_prereleases.yml@main
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     with:
       commit_sha: ${{ github.sha }}
       release_channel: stable
       dist_tag: canary,next
+      enableFailureNotification: true
     secrets:
+      DISCORD_WEBHOOK_URL: ${{ secrets.DISCORD_WEBHOOK_URL }}
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
   publish_prerelease_experimental:
     name: Publish to Experimental channel
     uses: facebook/react/.github/workflows/runtime_prereleases.yml@main
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     # NOTE: Intentionally running these jobs sequentially because npm
     # will sometimes fail if you try to concurrently publish two
     # different versions of the same package, even if they use different
@@ -33,5 +42,8 @@ jobs:
       commit_sha: ${{ github.sha }}
       release_channel: experimental
       dist_tag: experimental
+      enableFailureNotification: true
     secrets:
+      DISCORD_WEBHOOK_URL: ${{ secrets.DISCORD_WEBHOOK_URL }}
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/runtime_releases_from_npm_manual.yml

@@ -78,7 +78,9 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd scripts/release install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: cp ./scripts/release/ci-npmrc ~/.npmrc
       - if: '${{ inputs.only_packages }}'
         name: 'Prepare ${{ inputs.only_packages }} from NPM'

.github/workflows/shared_check_maintainer.yml

@@ -6,10 +6,6 @@ on:
       actor:
         required: true
         type: string
-      is_remote:
-        required: false
-        type: boolean
-        default: false
     outputs:
       is_core_team:
         value: ${{ jobs.check_maintainer.outputs.is_core_team }}
@@ -30,7 +26,6 @@ jobs:
     outputs:
       is_core_team: ${{ steps.check_if_actor_is_maintainer.outputs.result }}
     steps:
-      - uses: actions/checkout@v4
       - name: Check if actor is maintainer
         id: check_if_actor_is_maintainer
         uses: actions/github-script@v7
@@ -38,33 +33,20 @@ jobs:
           script: |
             const fs = require('fs');
             const actor = '${{ inputs.actor }}';
-            let isRemote = ${{ inputs.is_remote }};
-            if (typeof isRemote === 'string') {
-              isRemote = isRemote === 'true';
+            const res = await github.rest.repos.getContent({
+              owner: 'facebook',
+              repo: 'react',
+              path: 'MAINTAINERS',
+              ref: 'main',
+              headers: { Accept: 'application/vnd.github+json' }
+            });
+            if (res.status !== 200) {
+              console.error(res);
+              throw new Error('Unable to fetch MAINTAINERS file');
             }
-            if (typeof isRemote !== 'boolean') {
-              throw new Error(`Invalid \`isRemote\` input. Expected a boolean, got: ${isRemote}`);
-            }
-
-            let content = null;
-            if (isRemote === true) {
-              const res = await github.rest.repos.getContent({
-                owner: 'facebook',
-                repo: 'react',
-                path: 'MAINTAINERS',
-                ref: 'main',
-                headers: { Accept: 'application/vnd.github+json' }
-              });
-              if (res.status !== 200) {
-                console.error(res);
-                throw new Error('Unable to fetch MAINTAINERS file');
-              }
-              content = Buffer.from(res.data.content, 'base64').toString();
-            } else {
-              content = await fs.readFileSync('./MAINTAINERS', { encoding: 'utf8' });
-            }
-            if (content === null) {
-              throw new Error('Unable to retrieve local or http MAINTAINERS file');
+            content = Buffer.from(res.data.content, 'base64').toString();
+            if (content == null || typeof content !== 'string') {
+              throw new Error('Unable to retrieve MAINTAINERS file');
             }
 
             const maintainers = new Set(content.split('\n'));

.github/workflows/shared_cleanup_stale_branch_caches.yml

@@ -3,7 +3,8 @@
 name: (Shared) Cleanup Stale Branch Caches
 on:
   schedule:
-    - cron: 0 0 * * *
+    # Every 6 hours
+    - cron: 0 */6 * * *
   workflow_dispatch:
 
 permissions: {}

.github/workflows/shared_label_core_team_prs.yml

@@ -1,7 +1,8 @@
 name: (Shared) Label Core Team PRs
 
 on:
-  pull_request:
+  pull_request_target:
+    types: [opened]
 
 permissions: {}
 
@@ -11,7 +12,19 @@ env:
   SEGMENT_DOWNLOAD_TIMEOUT_MINS: 1
 
 jobs:
+  check_access:
+    runs-on: ubuntu-latest
+    outputs:
+      is_member_or_collaborator: ${{ steps.check_is_member_or_collaborator.outputs.is_member_or_collaborator }}
+    steps:
+      - name: Check is member or collaborator
+        id: check_is_member_or_collaborator
+        if: ${{ github.event.pull_request.author_association == 'MEMBER' || github.event.pull_request.author_association == 'COLLABORATOR' }}
+        run: echo "is_member_or_collaborator=true" >> "$GITHUB_OUTPUT"
+
   check_maintainer:
+    if: ${{ needs.check_access.outputs.is_member_or_collaborator == 'true' || needs.check_access.outputs.is_member_or_collaborator == true }}
+    needs: [check_access]
     uses: facebook/react/.github/workflows/shared_check_maintainer.yml@main
     permissions:
       # Used by check_maintainer

.github/workflows/shared_lint.yml

@@ -29,6 +29,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -36,6 +37,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn prettier-check
 
   eslint:
@@ -50,6 +52,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -57,6 +60,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: node ./scripts/tasks/eslint
 
   check_license:
@@ -71,6 +75,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -78,6 +83,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: ./scripts/ci/check_license.sh
 
   test_print_warnings:
@@ -92,6 +98,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -99,4 +106,5 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: ./scripts/ci/test_print_warnings.sh

.nvmrc

@@ -1 +1 @@
-v18.20.1
+v20.19.0

CHANGELOG-canary.md

@@ -1,18 +0,0 @@
-## March 22, 2024 (18.3.0-canary-670811593-20240322)
-
-## React
-- Added `useActionState` to replace `useFormState` and added `pending` value ([#28491](https://github.com/facebook/react/pull/28491)).
-
-## October 5, 2023 (18.3.0-canary-546178f91-20231005)
-
-### React
-
-- Added support for async functions to be passed to `startTransition`. 
-- `useTransition` now triggers the nearest error boundary instead of a global error.
-- Added `useOptimistic`, a new Hook for handling optimistic UI updates. It optimistically updates the UI before receiving confirmation from a server or external source.
-
-### React DOM
-
-- Added support for passing async functions to the `action` prop on `<form>`. When the function passed to `action` is marked with [`'use server'`](https://react.dev/reference/react/use-server), the form is [progressively enhanced](https://developer.mozilla.org/en-US/docs/Glossary/Progressive_Enhancement).
-- Added `useFormStatus`, a new Hook for checking the submission state of a form.
-- Added `useFormState`, a new Hook for updating state upon form submission. When the function passed to `useFormState` is marked with [`'use server'`](https://react.dev/reference/react/use-server), the update is [progressively enhanced](https://developer.mozilla.org/en-US/docs/Glossary/Progressive_Enhancement).

CHANGELOG.md

@@ -1,3 +1,50 @@
+## 19.1.0 (March 28, 2025)
+
+### Owner Stack
+
+An Owner Stack is a string representing the components that are directly responsible for rendering a particular component. You can log Owner Stacks when debugging or use Owner Stacks to enhance error overlays or other development tools. Owner Stacks are only available in development builds. Component Stacks in production are unchanged.
+
+* An Owner Stack is a development-only stack trace that helps identify which components are responsible for rendering a particular component. An Owner Stack is distinct from a Component Stacks, which shows the hierarchy of components leading to an error.
+* The [captureOwnerStack API](https://react.dev/reference/react/captureOwnerStack) is only available in development mode and returns a Owner Stack, if available. The API can be used to enhance error overlays or log component relationships when debugging. [#29923](https://github.com/facebook/react/pull/29923), [#32353](https://github.com/facebook/react/pull/32353), [#30306](https://github.com/facebook/react/pull/30306),
+[#32538](https://github.com/facebook/react/pull/32538), [#32529](https://github.com/facebook/react/pull/32529), [#32538](https://github.com/facebook/react/pull/32538)
+
+### React
+* Enhanced support for Suspense boundaries to be used anywhere, including the client, server, and during hydration. [#32069](https://github.com/facebook/react/pull/32069), [#32163](https://github.com/facebook/react/pull/32163), [#32224](https://github.com/facebook/react/pull/32224), [#32252](https://github.com/facebook/react/pull/32252)
+* Reduced unnecessary client rendering through improved hydration scheduling [#31751](https://github.com/facebook/react/pull/31751)
+* Increased priority of client rendered Suspense boundaries [#31776](https://github.com/facebook/react/pull/31776)
+* Fixed frozen fallback states by rendering unfinished Suspense boundaries on the client. [#31620](https://github.com/facebook/react/pull/31620)
+* Reduced garbage collection pressure by improving Suspense boundary retries. [#31667](https://github.com/facebook/react/pull/31667)
+* Fixed erroneous “Waiting for Paint” log when the passive effect phase was not delayed [#31526](https://github.com/facebook/react/pull/31526)
+* Fixed a regression causing key warnings for flattened positional children in development mode. [#32117](https://github.com/facebook/react/pull/32117)
+* Updated `useId` to use valid CSS selectors, changing format from `:r123:` to `«r123»`. [#32001](https://github.com/facebook/react/pull/32001)
+* Added a dev-only warning for null/undefined created in useEffect, useInsertionEffect, and useLayoutEffect. [#32355](https://github.com/facebook/react/pull/32355)
+* Fixed a bug where dev-only methods were exported in production builds. React.act is no longer available in production builds. [#32200](https://github.com/facebook/react/pull/32200)
+* Improved consistency across prod and dev to improve compatibility with Google Closure Complier and bindings [#31808](https://github.com/facebook/react/pull/31808)
+* Improve passive effect scheduling for consistent task yielding. [#31785](https://github.com/facebook/react/pull/31785)
+* Fixed asserts in React Native when passChildrenWhenCloningPersistedNodes is enabled for OffscreenComponent rendering. [#32528](https://github.com/facebook/react/pull/32528)
+* Fixed component name resolution for Portal [#32640](https://github.com/facebook/react/pull/32640)
+* Added support for beforetoggle and toggle events on the dialog element. #32479 [#32479](https://github.com/facebook/react/pull/32479)
+
+### React DOM
+* Fixed double warning when the `href` attribute is an empty string [#31783](https://github.com/facebook/react/pull/31783)
+ * Fixed an edge case where `getHoistableRoot()` didn’t work properly when the container was a Document [#32321](https://github.com/facebook/react/pull/32321)
+* Removed support for using HTML comments (e.g. `<!-- -->`) as a DOM container. [#32250](https://github.com/facebook/react/pull/32250)
+* Added support for `<script>` and `<template>` tags to be nested within `<select>` tags. [#31837](https://github.com/facebook/react/pull/31837)
+* Fixed responsive images to be preloaded as HTML instead of headers [#32445](https://github.com/facebook/react/pull/32445)
+
+### use-sync-external-store
+* Added `exports` field to `package.json` for `use-sync-external-store` to support various entrypoints. [#25231](https://github.com/facebook/react/pull/25231)
+
+### React Server Components
+* Added `unstable_prerender`, a new experimental API for prerendering React Server Components on the server [#31724](https://github.com/facebook/react/pull/31724)
+* Fixed an issue where streams would hang when receiving new chunks after a global error [#31840](https://github.com/facebook/react/pull/31840), [#31851](https://github.com/facebook/react/pull/31851)
+* Fixed an issue where pending chunks were counted twice. [#31833](https://github.com/facebook/react/pull/31833)
+* Added support for streaming in edge environments [#31852](https://github.com/facebook/react/pull/31852)
+* Added support for sending custom error names from a server so that they are available in the client for console replaying. [#32116](https://github.com/facebook/react/pull/32116)
+* Updated the server component wire format to remove IDs for hints and console.log because they have no return value [#31671](https://github.com/facebook/react/pull/31671)
+* Exposed `registerServerReference` in client builds to handle server references in different environments. [#32534](https://github.com/facebook/react/pull/32534)
+* Added react-server-dom-parcel package which integrates Server Components with the [Parcel bundler](https://parceljs.org/) [#31725](https://github.com/facebook/react/pull/31725), [#32132](https://github.com/facebook/react/pull/32132), [#31799](https://github.com/facebook/react/pull/31799), [#32294](https://github.com/facebook/react/pull/32294), [#31741](https://github.com/facebook/react/pull/31741)
+
 ## 19.0.0 (December 5, 2024)
 
 Below is a list of all new features, APIs, deprecations, and breaking changes. Read [React 19 release post](https://react.dev/blog/2024/04/25/react-19) and [React 19 upgrade guide](https://react.dev/blog/2024/04/25/react-19-upgrade-guide) for more information.

ReactVersions.js

@@ -18,7 +18,7 @@
 //
 //   0.0.0-experimental-241c4467e-20200129
 
-const ReactVersion = '19.1.0';
+const ReactVersion = '19.2.0';
 
 // The label used by the @canary channel. Represents the upcoming release's
 // stability. Most of the time, this will be "canary", but we may temporarily
@@ -33,7 +33,7 @@ const canaryChannelLabel = 'canary';
 const rcNumber = 0;
 
 const stablePackages = {
-  'eslint-plugin-react-hooks': '5.2.0',
+  'eslint-plugin-react-hooks': '6.1.0',
   'jest-react': '0.17.0',
   react: ReactVersion,
   'react-art': ReactVersion,
@@ -42,12 +42,12 @@ const stablePackages = {
   'react-server-dom-turbopack': ReactVersion,
   'react-server-dom-parcel': ReactVersion,
   'react-is': ReactVersion,
-  'react-reconciler': '0.32.0',
-  'react-refresh': '0.17.0',
+  'react-reconciler': '0.33.0',
+  'react-refresh': '0.18.0',
   'react-test-renderer': ReactVersion,
-  'use-subscription': '1.11.0',
-  'use-sync-external-store': '1.5.0',
-  scheduler: '0.26.0',
+  'use-subscription': '1.12.0',
+  'use-sync-external-store': '1.6.0',
+  scheduler: '0.27.0',
 };
 
 // These packages do not exist in the @canary or @latest channel, only

compiler/CHANGELOG.md

@@ -0,0 +1,59 @@
+## 19.1.0-rc.1 (April 21, 2025)
+
+## eslint-plugin-react-hooks
+* Temporarily disable ref access in render validation [#32839](https://github.com/facebook/react/pull/32839) by [@poteto](https://github.com/poteto)
+* Fix type error with recommended config [#32666](https://github.com/facebook/react/pull/32666) by [@niklasholm](https://github.com/niklasholm)
+* Merge rule from eslint-plugin-react-compiler into `react-hooks` plugin [#32416](https://github.com/facebook/react/pull/32416) by [@michaelfaith](https://github.com/michaelfaith)
+* Add dev dependencies for typescript migration [#32279](https://github.com/facebook/react/pull/32279) by [@michaelfaith](https://github.com/michaelfaith)
+* Support v9 context api [#32045](https://github.com/facebook/react/pull/32045) by [@michaelfaith](https://github.com/michaelfaith)
+* Support eslint 8+ flat plugin syntax out of the box for eslint-plugin-react-compiler [#32120](https://github.com/facebook/react/pull/32120) by [@orta](https://github.com/orta)
+
+## babel-plugin-react-compiler
+* Support satisfies operator [#32742](https://github.com/facebook/react/pull/32742) by [@rodrigofariow](https://github.com/rodrigofariow)
+* Fix inferEffectDependencies lint false positives [#32769](https://github.com/facebook/react/pull/32769) by [@mofeiZ](https://github.com/mofeiZ)
+* Fix hoisting of let declarations [#32724](https://github.com/facebook/react/pull/32724) by [@mofeiZ](https://github.com/mofeiZ)
+* Avoid failing builds when import specifiers conflict or shadow vars [#32663](https://github.com/facebook/react/pull/32663) by [@mofeiZ](https://github.com/mofeiZ)
+* Optimize components declared with arrow function and implicit return and `compilationMode: 'infer'` [#31792](https://github.com/facebook/react/pull/31792) by [@dimaMachina](https://github.com/dimaMachina)
+* Validate static components [#32683](https://github.com/facebook/react/pull/32683) by [@josephsavona](https://github.com/josephsavona)
+* Hoist dependencies from functions more conservatively [#32616](https://github.com/facebook/react/pull/32616) by [@mofeiZ](https://github.com/mofeiZ)
+* Implement NumericLiteral as ObjectPropertyKey [#31791](https://github.com/facebook/react/pull/31791) by [@dimaMachina](https://github.com/dimaMachina)
+* Avoid bailouts when inserting gating [#32598](https://github.com/facebook/react/pull/32598) by [@mofeiZ](https://github.com/mofeiZ)
+* Stop bailing out early for hoisted gated functions [#32597](https://github.com/facebook/react/pull/32597) by [@mofeiZ](https://github.com/mofeiZ)
+* Add shape for Array.from [#32522](https://github.com/facebook/react/pull/32522) by [@mofeiZ](https://github.com/mofeiZ)
+* Patch array and argument spread mutability [#32521](https://github.com/facebook/react/pull/32521) by [@mofeiZ](https://github.com/mofeiZ)
+* Make CompilerError compatible with reflection [#32539](https://github.com/facebook/react/pull/32539) by [@poteto](https://github.com/poteto)
+* Add simple walltime measurement [#32331](https://github.com/facebook/react/pull/32331) by [@poteto](https://github.com/poteto)
+* Improve error messages for unhandled terminal and instruction kinds [#32324](https://github.com/facebook/react/pull/32324) by [@inottn](https://github.com/inottn)
+* Handle TSInstantiationExpression in lowerExpression [#32302](https://github.com/facebook/react/pull/32302) by [@inottn](https://github.com/inottn)
+* Fix invalid Array.map type [#32095](https://github.com/facebook/react/pull/32095) by [@mofeiZ](https://github.com/mofeiZ)
+* Patch for JSX escape sequences in @babel/generator [#32131](https://github.com/facebook/react/pull/32131) by [@mofeiZ](https://github.com/mofeiZ)
+* `JSXText` emits incorrect with bracket [#32138](https://github.com/facebook/react/pull/32138) by [@himself65](https://github.com/himself65)
+* Validation against calling impure functions [#31960](https://github.com/facebook/react/pull/31960) by [@josephsavona](https://github.com/josephsavona)
+* Always target node [#32091](https://github.com/facebook/react/pull/32091) by [@poteto](https://github.com/poteto)
+* Patch compilationMode:infer object method edge case [#32055](https://github.com/facebook/react/pull/32055) by [@mofeiZ](https://github.com/mofeiZ)
+* Generate ts defs [#31994](https://github.com/facebook/react/pull/31994) by [@poteto](https://github.com/poteto)
+* Relax react peer dep requirement [#31915](https://github.com/facebook/react/pull/31915) by [@poteto](https://github.com/poteto)
+* Allow type cast expressions with refs [#31871](https://github.com/facebook/react/pull/31871) by [@josephsavona](https://github.com/josephsavona)
+* Add shape for global Object.keys [#31583](https://github.com/facebook/react/pull/31583) by [@mofeiZ](https://github.com/mofeiZ)
+* Optimize method calls w props receiver [#31775](https://github.com/facebook/react/pull/31775) by [@josephsavona](https://github.com/josephsavona)
+* Fix dropped ref with spread props in InlineJsxTransform [#31726](https://github.com/facebook/react/pull/31726) by [@jackpope](https://github.com/jackpope)
+* Support for non-declatation for in/of iterators [#31710](https://github.com/facebook/react/pull/31710) by [@mvitousek](https://github.com/mvitousek)
+* Support for context variable loop iterators [#31709](https://github.com/facebook/react/pull/31709) by [@mvitousek](https://github.com/mvitousek)
+* Replace deprecated dependency in `eslint-plugin-react-compiler` [#31629](https://github.com/facebook/react/pull/31629) by [@rakleed](https://github.com/rakleed)
+* Support enableRefAsProp in jsx transform [#31558](https://github.com/facebook/react/pull/31558) by [@jackpope](https://github.com/jackpope)
+* Fix: ref.current now correctly reactive [#31521](https://github.com/facebook/react/pull/31521) by [@mofeiZ](https://github.com/mofeiZ)
+* Outline JSX with non-jsx children [#31442](https://github.com/facebook/react/pull/31442) by [@gsathya](https://github.com/gsathya)
+* Outline jsx with duplicate attributes [#31441](https://github.com/facebook/react/pull/31441) by [@gsathya](https://github.com/gsathya)
+* Store original and new prop names [#31440](https://github.com/facebook/react/pull/31440) by [@gsathya](https://github.com/gsathya)
+* Stabilize compiler output: sort deps and decls by name [#31362](https://github.com/facebook/react/pull/31362) by [@mofeiZ](https://github.com/mofeiZ)
+* Bugfix for hoistable deps for nested functions [#31345](https://github.com/facebook/react/pull/31345) by [@mofeiZ](https://github.com/mofeiZ)
+* Remove compiler runtime-compat fixture library [#31430](https://github.com/facebook/react/pull/31430) by [@poteto](https://github.com/poteto)
+* Wrap inline jsx transform codegen in conditional [#31267](https://github.com/facebook/react/pull/31267) by [@jackpope](https://github.com/jackpope)
+* Check if local identifier is a hook when resolving globals [#31384](https://github.com/facebook/react/pull/31384) by [@poteto](https://github.com/poteto)
+* Handle member expr as computed property [#31344](https://github.com/facebook/react/pull/31344) by [@gsathya](https://github.com/gsathya)
+* Fix to ref access check to ban ref?.current [#31360](https://github.com/facebook/react/pull/31360) by [@mvitousek](https://github.com/mvitousek)
+* InlineJSXTransform transforms jsx inside function expressions [#31282](https://github.com/facebook/react/pull/31282) by [@josephsavona](https://github.com/josephsavona)
+
+## Other
+* Add shebang to banner [#32225](https://github.com/facebook/react/pull/32225) by [@Jeremy-Hibiki](https://github.com/Jeremy-Hibiki)
+* remove terser from react-compiler-runtime build [#31326](https://github.com/facebook/react/pull/31326) by [@henryqdineen](https://github.com/henryqdineen)

compiler/apps/playground/components/Editor/EditorImpl.tsx

@@ -19,7 +19,9 @@ import BabelPluginReactCompiler, {
   PluginOptions,
   CompilerPipelineValue,
   parsePluginOptions,
-} from 'babel-plugin-react-compiler/src';
+  printReactiveFunctionWithOutlined,
+  printFunctionWithOutlined,
+} from 'babel-plugin-react-compiler';
 import clsx from 'clsx';
 import invariant from 'invariant';
 import {useSnackbar} from 'notistack';
@@ -41,8 +43,6 @@ import {
   default as Output,
   PrintedCompilerPipelineValue,
 } from './Output';
-import {printFunctionWithOutlined} from 'babel-plugin-react-compiler/src/HIR/PrintHIR';
-import {printReactiveFunctionWithOutlined} from 'babel-plugin-react-compiler/src/ReactiveScopes/PrintReactiveFunction';
 import {transformFromAstSync} from '@babel/core';
 
 function parseInput(

compiler/apps/playground/components/Editor/Input.tsx

@@ -6,7 +6,7 @@
  */
 
 import MonacoEditor, {loader, type Monaco} from '@monaco-editor/react';
-import {CompilerErrorDetail} from 'babel-plugin-react-compiler/src';
+import {CompilerErrorDetail} from 'babel-plugin-react-compiler';
 import invariant from 'invariant';
 import type {editor} from 'monaco-editor';
 import * as monaco from 'monaco-editor';

compiler/apps/playground/components/Editor/Output.tsx

@@ -11,7 +11,7 @@ import {
   InformationCircleIcon,
 } from '@heroicons/react/outline';
 import MonacoEditor, {DiffEditor} from '@monaco-editor/react';
-import {type CompilerError} from 'babel-plugin-react-compiler/src';
+import {type CompilerError} from 'babel-plugin-react-compiler';
 import parserBabel from 'prettier/plugins/babel';
 import * as prettierPluginEstree from 'prettier/plugins/estree';
 import * as prettier from 'prettier/standalone';

compiler/apps/playground/lib/reactCompilerMonacoDiagnostics.ts

@@ -6,10 +6,7 @@
  */
 
 import {Monaco} from '@monaco-editor/react';
-import {
-  CompilerErrorDetail,
-  ErrorSeverity,
-} from 'babel-plugin-react-compiler/src';
+import {CompilerErrorDetail, ErrorSeverity} from 'babel-plugin-react-compiler';
 import {MarkerSeverity, type editor} from 'monaco-editor';
 
 function mapReactCompilerSeverityToMonaco(
@@ -54,7 +51,7 @@ export function renderReactCompilerMarkers({
   model,
   details,
 }: ReactCompilerMarkerConfig): void {
-  let markers = [];
+  const markers: Array<editor.IMarkerData> = [];
   for (const detail of details) {
     const marker = mapReactCompilerDiagnosticToMonacoMarker(detail, monaco);
     if (marker == null) {

compiler/apps/playground/package.json

@@ -4,7 +4,7 @@
   "private": true,
   "scripts": {
     "dev": "cd ../.. && concurrently --kill-others -n compiler,runtime,playground \"yarn workspace babel-plugin-react-compiler run watch\" \"yarn workspace react-compiler-runtime run watch\" \"wait-on packages/babel-plugin-react-compiler/dist/index.js && cd apps/playground && NODE_ENV=development next dev\"",
-    "build:compiler": "cd ../.. && concurrently -n compiler,runtime \"yarn workspace babel-plugin-react-compiler run build\" \"yarn workspace react-compiler-runtime run build\"",
+    "build:compiler": "cd ../.. && concurrently -n compiler,runtime \"yarn workspace babel-plugin-react-compiler run build --dts\" \"yarn workspace react-compiler-runtime run build\"",
     "build": "yarn build:compiler && next build",
     "postbuild": "node ./scripts/downloadFonts.js",
     "preinstall": "cd ../.. && yarn install --frozen-lockfile",
@@ -27,7 +27,7 @@
     "@babel/types": "7.26.3",
     "@heroicons/react": "^1.0.6",
     "@monaco-editor/react": "^4.4.6",
-    "@playwright/test": "^1.42.1",
+    "@playwright/test": "^1.51.1",
     "@use-gesture/react": "^10.2.22",
     "hermes-eslint": "^0.25.0",
     "hermes-parser": "^0.25.0",

compiler/apps/playground/yarn.lock

@@ -781,12 +781,12 @@
   resolved "https://registry.yarnpkg.com/@pkgjs/parseargs/-/parseargs-0.11.0.tgz#a77ea742fab25775145434eb1d2328cf5013ac33"
   integrity sha512-+1VkjdD0QBLPodGrJUeqarH8VAIvQODIbwh9XpP5Syisf7YoQgsJKPNFoqqLQlu+VQ/tVSshMR6loPMn8U+dPg==
 
-"@playwright/test@^1.42.1":
-  version "1.47.2"
-  resolved "https://registry.yarnpkg.com/@playwright/test/-/test-1.47.2.tgz#dbe7051336bfc5cc599954214f9111181dbc7475"
-  integrity sha512-jTXRsoSPONAs8Za9QEQdyjFn+0ZQFjCiIztAIF6bi1HqhBzG9Ma7g1WotyiGqFSBRZjIEqMdT8RUlbk1QVhzCQ==
+"@playwright/test@^1.51.1":
+  version "1.51.1"
+  resolved "https://registry.yarnpkg.com/@playwright/test/-/test-1.51.1.tgz#75357d513221a7be0baad75f01e966baf9c41a2e"
+  integrity sha512-nM+kEaTSAoVlXmMPH10017vn3FSiFqr/bh4fKg9vmAdMfd9SDqRZNvPSiAHADc/itWak+qPvMPZQOPwCBW7k7Q==
   dependencies:
-    playwright "1.47.2"
+    playwright "1.51.1"
 
 "@rtsao/scc@^1.1.0":
   version "1.1.0"
@@ -1249,14 +1249,14 @@ camelcase-css@^2.0.1:
   integrity sha512-QOSvevhslijgYwRx6Rv7zKdMF8lbRmx+uQGx2+vDc+KI/eBnsy9kit5aj23AgGu3pa4t9AgwbnXWqS+iOY+2aA==
 
 caniuse-lite@^1.0.30001579:
-  version "1.0.30001669"
-  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30001669.tgz#fda8f1d29a8bfdc42de0c170d7f34a9cf19ed7a3"
-  integrity sha512-DlWzFDJqstqtIVx1zeSpIMLjunf5SmwOw0N2Ck/QSQdS8PLS4+9HrLaYei4w8BIAL7IB/UEDu889d8vhCTPA0w==
+  version "1.0.30001715"
+  resolved "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001715.tgz"
+  integrity sha512-7ptkFGMm2OAOgvZpwgA4yjQ5SQbrNVGdRjzH0pBdy1Fasvcr+KAeECmbCAECzTuDuoX0FCY8KzUxjf9+9kfZEw==
 
 caniuse-lite@^1.0.30001646, caniuse-lite@^1.0.30001663:
-  version "1.0.30001664"
-  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30001664.tgz#d588d75c9682d3301956b05a3749652a80677df4"
-  integrity sha512-AmE7k4dXiNKQipgn7a2xg558IRqPN3jMQY/rOsbxDhrd0tyChwbITBfiwtnqz8bi2M5mIWbxAYBvk7W7QBUS2g==
+  version "1.0.30001715"
+  resolved "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001715.tgz"
+  integrity sha512-7ptkFGMm2OAOgvZpwgA4yjQ5SQbrNVGdRjzH0pBdy1Fasvcr+KAeECmbCAECzTuDuoX0FCY8KzUxjf9+9kfZEw==
 
 chalk@^2.4.2:
   version "2.4.2"
@@ -3008,17 +3008,17 @@ pirates@^4.0.1:
   resolved "https://registry.yarnpkg.com/pirates/-/pirates-4.0.6.tgz#3018ae32ecfcff6c29ba2267cbf21166ac1f36b9"
   integrity sha512-saLsH7WeYYPiD25LDuLRRY/i+6HaPYr6G1OUlN39otzkSTxKnubR9RTxS3/Kk50s1g2JTgFwWQDQyplC5/SHZg==
 
-playwright-core@1.47.2:
-  version "1.47.2"
-  resolved "https://registry.yarnpkg.com/playwright-core/-/playwright-core-1.47.2.tgz#7858da9377fa32a08be46ba47d7523dbd9460a4e"
-  integrity sha512-3JvMfF+9LJfe16l7AbSmU555PaTl2tPyQsVInqm3id16pdDfvZ8TTZ/pyzmkbDrZTQefyzU7AIHlZqQnxpqHVQ==
+playwright-core@1.51.1:
+  version "1.51.1"
+  resolved "https://registry.yarnpkg.com/playwright-core/-/playwright-core-1.51.1.tgz#d57f0393e02416f32a47cf82b27533656a8acce1"
+  integrity sha512-/crRMj8+j/Nq5s8QcvegseuyeZPxpQCZb6HNk3Sos3BlZyAknRjoyJPFWkpNn8v0+P3WiwqFF8P+zQo4eqiNuw==
 
-playwright@1.47.2:
-  version "1.47.2"
-  resolved "https://registry.yarnpkg.com/playwright/-/playwright-1.47.2.tgz#155688aa06491ee21fb3e7555b748b525f86eb20"
-  integrity sha512-nx1cLMmQWqmA3UsnjaaokyoUpdVaaDhJhMoxX2qj3McpjnsqFHs516QAKYhqHAgOP+oCFTEOCOAaD1RgD/RQfA==
+playwright@1.51.1:
+  version "1.51.1"
+  resolved "https://registry.yarnpkg.com/playwright/-/playwright-1.51.1.tgz#ae1467ee318083968ad28d6990db59f47a55390f"
+  integrity sha512-kkx+MB2KQRkyxjYPc3a0wLZZoDczmppyGJIvQ43l+aZihkaVvmu/21kiyaHeHjiFxjxNNFnUncKmcGIyOojsaw==
   dependencies:
-    playwright-core "1.47.2"
+    playwright-core "1.51.1"
   optionalDependencies:
     fsevents "2.3.2"
 

compiler/package.json

@@ -37,7 +37,7 @@
     "prettier": "^3.3.3",
     "prettier-plugin-hermes-parser": "^0.26.0",
     "prompt-promise": "^1.0.3",
-    "rimraf": "^5.0.10",
+    "rimraf": "^6.0.1",
     "to-fast-properties": "^2.0.0",
     "tsup": "^8.4.0",
     "typescript": "^5.4.3",
@@ -45,7 +45,6 @@
     "yargs": "^17.7.2"
   },
   "resolutions": {
-    "rimraf": "5.0.10",
     "@babel/types": "7.26.3"
   },
   "packageManager": "yarn@1.22.22"

compiler/packages/babel-plugin-react-compiler/package.json

@@ -12,12 +12,12 @@
     "build": "rimraf dist && tsup",
     "test": "./scripts/link-react-compiler-runtime.sh && yarn snap:ci",
     "jest": "yarn build && ts-node node_modules/.bin/jest",
-    "snap": "node ../snap/dist/main.js",
+    "snap": "yarn workspace snap run snap",
     "snap:build": "yarn workspace snap run build",
     "snap:ci": "yarn snap:build && yarn snap",
     "ts:analyze-trace": "scripts/ts-analyze-trace.sh",
     "lint": "yarn eslint src",
-    "watch": "yarn build --watch"
+    "watch": "yarn build --dts --watch"
   },
   "dependencies": {
     "@babel/types": "^7.26.0"

compiler/packages/babel-plugin-react-compiler/src/Babel/BabelPlugin.ts

@@ -73,7 +73,7 @@ export default function BabelPluginReactCompiler(
             pass.filename ?? null,
             opts.logger,
             opts.environment,
-            result?.retryErrors ?? [],
+            result,
           );
           if (ENABLE_REACT_COMPILER_TIMINGS === true) {
             performance.mark(`${filename}:end`, {

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Options.ts

@@ -182,7 +182,9 @@ export type LoggerEvent =
   | CompileDiagnosticEvent
   | CompileSkipEvent
   | PipelineErrorEvent
-  | TimingEvent;
+  | TimingEvent
+  | AutoDepsDecorationsEvent
+  | AutoDepsEligibleEvent;
 
 export type CompileErrorEvent = {
   kind: 'CompileError';
@@ -219,6 +221,16 @@ export type TimingEvent = {
   kind: 'Timing';
   measurement: PerformanceMeasure;
 };
+export type AutoDepsDecorationsEvent = {
+  kind: 'AutoDepsDecorations';
+  fnLoc: t.SourceLocation;
+  decorations: Array<t.SourceLocation>;
+};
+export type AutoDepsEligibleEvent = {
+  kind: 'AutoDepsEligible';
+  fnLoc: t.SourceLocation;
+  depArrayLoc: t.SourceLocation;
+};
 
 export type Logger = {
   logEvent: (filename: string | null, event: LoggerEvent) => void;

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Pipeline.ts

@@ -392,6 +392,11 @@ function runWithEnvironment(
 
   if (env.config.inferEffectDependencies) {
     inferEffectDependencies(hir);
+    log({
+      kind: 'hir',
+      name: 'InferEffectDependencies',
+      value: hir,
+    });
   }
 
   if (env.config.inlineJsxTransform) {

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Program.ts

@@ -30,6 +30,7 @@ import {
   findProgramSuppressions,
   suppressionsToCompilerError,
 } from './Suppression';
+import {GeneratedSource} from '../HIR';
 
 export type CompilerPass = {
   opts: PluginOptions;
@@ -267,8 +268,9 @@ function isFilePartOfSources(
   return false;
 }
 
-type CompileProgramResult = {
+export type CompileProgramResult = {
   retryErrors: Array<{fn: BabelFn; error: CompilerError}>;
+  inferredEffectLocations: Set<t.SourceLocation>;
 };
 /**
  * `compileProgram` is directly invoked by the react-compiler babel plugin, so
@@ -369,6 +371,7 @@ export function compileProgram(
     },
   );
   const retryErrors: Array<{fn: BabelFn; error: CompilerError}> = [];
+  const inferredEffectLocations = new Set<t.SourceLocation>();
   const processFn = (
     fn: BabelFn,
     fnType: ReactFunctionType,
@@ -466,6 +469,23 @@ export function compileProgram(
       }
     }
 
+    /**
+     * Otherwise if 'use no forget/memo' is present, we still run the code through the compiler
+     * for validation but we don't mutate the babel AST. This allows us to flag if there is an
+     * unused 'use no forget/memo' directive.
+     */
+    if (pass.opts.ignoreUseNoForget === false && optOutDirectives.length > 0) {
+      for (const directive of optOutDirectives) {
+        pass.opts.logger?.logEvent(pass.filename, {
+          kind: 'CompileSkip',
+          fnLoc: fn.node.body.loc ?? null,
+          reason: `Skipped due to '${directive.value.value}' directive.`,
+          loc: directive.loc ?? null,
+        });
+      }
+      return null;
+    }
+
     pass.opts.logger?.logEvent(pass.filename, {
       kind: 'CompileSuccess',
       fnLoc: fn.node.loc ?? null,
@@ -489,26 +509,17 @@ export function compileProgram(
       return null;
     }
 
-    /**
-     * Otherwise if 'use no forget/memo' is present, we still run the code through the compiler
-     * for validation but we don't mutate the babel AST. This allows us to flag if there is an
-     * unused 'use no forget/memo' directive.
-     */
-    if (pass.opts.ignoreUseNoForget === false && optOutDirectives.length > 0) {
-      for (const directive of optOutDirectives) {
-        pass.opts.logger?.logEvent(pass.filename, {
-          kind: 'CompileSkip',
-          fnLoc: fn.node.body.loc ?? null,
-          reason: `Skipped due to '${directive.value.value}' directive.`,
-          loc: directive.loc ?? null,
-        });
-      }
-      return null;
-    }
-
     if (!pass.opts.noEmit) {
       return compileResult.compiledFn;
     }
+    /**
+     * inferEffectDependencies + noEmit is currently only used for linting. In
+     * this mode, add source locations for where the compiler *can* infer effect
+     * dependencies.
+     */
+    for (const loc of compileResult.compiledFn.inferredEffectLocations) {
+      if (loc !== GeneratedSource) inferredEffectLocations.add(loc);
+    }
     return null;
   };
 
@@ -587,7 +598,7 @@ export function compileProgram(
   if (compiledFns.length > 0) {
     addImportsToProgram(program, programContext);
   }
-  return {retryErrors};
+  return {retryErrors, inferredEffectLocations};
 }
 
 function shouldSkipCompilation(

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Reanimated.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import type * as BabelCore from '@babel/core';
 import {hasOwnProperty} from '../Utils/utils';
 import {PluginOptions} from './Options';

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/ValidateNoUntransformedReferences.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {NodePath} from '@babel/core';
 import * as t from '@babel/types';
 
@@ -11,6 +18,7 @@ import {
 import {getOrInsertWith} from '../Utils/utils';
 import {Environment} from '../HIR';
 import {DEFAULT_EXPORT} from '../HIR/Environment';
+import {CompileProgramResult} from './Program';
 
 function throwInvalidReact(
   options: Omit<CompilerErrorDetailOptions, 'severity'>,
@@ -36,12 +44,16 @@ function assertValidEffectImportReference(
     const parent = path.parentPath;
     if (parent != null && parent.isCallExpression()) {
       const args = parent.get('arguments');
+      const maybeCalleeLoc = path.node.loc;
+      const hasInferredEffect =
+        maybeCalleeLoc != null &&
+        context.inferredEffectLocations.has(maybeCalleeLoc);
       /**
        * Only error on untransformed references of the form `useMyEffect(...)`
        * or `moduleNamespace.useMyEffect(...)`, with matching argument counts.
        * TODO: do we also want a mode to also hard error on non-call references?
        */
-      if (args.length === numArgs) {
+      if (args.length === numArgs && !hasInferredEffect) {
         const maybeErrorDiagnostic = matchCompilerDiagnostic(
           path,
           context.transformErrors,
@@ -97,7 +109,7 @@ export default function validateNoUntransformedReferences(
   filename: string | null,
   logger: Logger | null,
   env: EnvironmentConfig,
-  transformErrors: Array<{fn: NodePath<t.Node>; error: CompilerError}>,
+  compileResult: CompileProgramResult | null,
 ): void {
   const moduleLoadChecks = new Map<
     string,
@@ -126,7 +138,7 @@ export default function validateNoUntransformedReferences(
     }
   }
   if (moduleLoadChecks.size > 0) {
-    transformProgram(path, moduleLoadChecks, filename, logger, transformErrors);
+    transformProgram(path, moduleLoadChecks, filename, logger, compileResult);
   }
 }
 
@@ -136,6 +148,7 @@ type TraversalState = {
   logger: Logger | null;
   filename: string | null;
   transformErrors: Array<{fn: NodePath<t.Node>; error: CompilerError}>;
+  inferredEffectLocations: Set<t.SourceLocation>;
 };
 type CheckInvalidReferenceFn = (
   paths: Array<NodePath<t.Node>>,
@@ -223,14 +236,16 @@ function transformProgram(
   moduleLoadChecks: Map<string, Map<string, CheckInvalidReferenceFn>>,
   filename: string | null,
   logger: Logger | null,
-  transformErrors: Array<{fn: NodePath<t.Node>; error: CompilerError}>,
+  compileResult: CompileProgramResult | null,
 ): void {
   const traversalState: TraversalState = {
     shouldInvalidateScopes: true,
     program: path,
     filename,
     logger,
-    transformErrors,
+    transformErrors: compileResult?.retryErrors ?? [],
+    inferredEffectLocations:
+      compileResult?.inferredEffectLocations ?? new Set(),
   };
   path.traverse({
     ImportDeclaration(path: NodePath<t.ImportDeclaration>) {

compiler/packages/babel-plugin-react-compiler/src/HIR/AssertValidBlockNesting.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {CompilerError} from '..';
 import {
   BlockId,

compiler/packages/babel-plugin-react-compiler/src/HIR/BuildHIR.ts

@@ -2406,6 +2406,19 @@ function lowerExpression(
         kind: 'TypeCastExpression',
         value: lowerExpressionToTemporary(builder, expr.get('expression')),
         typeAnnotation: typeAnnotation.node,
+        typeAnnotationKind: 'cast',
+        type: lowerType(typeAnnotation.node),
+        loc: exprLoc,
+      };
+    }
+    case 'TSSatisfiesExpression': {
+      let expr = exprPath as NodePath<t.TSSatisfiesExpression>;
+      const typeAnnotation = expr.get('typeAnnotation');
+      return {
+        kind: 'TypeCastExpression',
+        value: lowerExpressionToTemporary(builder, expr.get('expression')),
+        typeAnnotation: typeAnnotation.node,
+        typeAnnotationKind: 'satisfies',
         type: lowerType(typeAnnotation.node),
         loc: exprLoc,
       };
@@ -2417,6 +2430,7 @@ function lowerExpression(
         kind: 'TypeCastExpression',
         value: lowerExpressionToTemporary(builder, expr.get('expression')),
         typeAnnotation: typeAnnotation.node,
+        typeAnnotationKind: 'as',
         type: lowerType(typeAnnotation.node),
         loc: exprLoc,
       };

compiler/packages/babel-plugin-react-compiler/src/HIR/BuildReactiveScopeTerminalsHIR.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {CompilerError} from '../CompilerError';
 import {getScopes, recursivelyTraverseItems} from './AssertValidBlockNesting';
 import {Environment} from './Environment';

compiler/packages/babel-plugin-react-compiler/src/HIR/CollectHoistablePropertyLoads.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {CompilerError} from '../CompilerError';
 import {inRange} from '../ReactiveScopes/InferReactiveScopeVariables';
 import {printDependency} from '../ReactiveScopes/PrintReactiveFunction';

compiler/packages/babel-plugin-react-compiler/src/HIR/CollectOptionalChainDependencies.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {CompilerError} from '..';
 import {assertNonNull} from './CollectHoistablePropertyLoads';
 import {

compiler/packages/babel-plugin-react-compiler/src/HIR/Environment.ts

@@ -11,6 +11,7 @@ import {fromZodError} from 'zod-validation-error';
 import {CompilerError} from '../CompilerError';
 import {
   CompilationMode,
+  defaultOptions,
   Logger,
   PanicThresholdOptions,
   parsePluginOptions,
@@ -779,6 +780,7 @@ export function parseConfigPragmaForTests(
   const environment = parseConfigPragmaEnvironmentForTest(pragma);
   let compilationMode: CompilationMode = defaults.compilationMode;
   let panicThreshold: PanicThresholdOptions = 'all_errors';
+  let noEmit: boolean = defaultOptions.noEmit;
   for (const token of pragma.split(' ')) {
     if (!token.startsWith('@')) {
       continue;
@@ -804,12 +806,17 @@ export function parseConfigPragmaForTests(
         panicThreshold = 'none';
         break;
       }
+      case '@noEmit': {
+        noEmit = true;
+        break;
+      }
     }
   }
   return parsePluginOptions({
     environment,
     compilationMode,
     panicThreshold,
+    noEmit,
   });
 }
 
@@ -852,6 +859,7 @@ export class Environment {
   programContext: ProgramContext;
   hasFireRewrite: boolean;
   hasInferredEffect: boolean;
+  inferredEffectLocations: Set<SourceLocation> = new Set();
 
   #contextIdentifiers: Set<t.Identifier>;
   #hoistedIdentifiers: Set<t.Identifier>;

compiler/packages/babel-plugin-react-compiler/src/HIR/Globals.ts

@@ -9,6 +9,7 @@ import {Effect, ValueKind, ValueReason} from './HIR';
 import {
   BUILTIN_SHAPES,
   BuiltInArrayId,
+  BuiltInFireFunctionId,
   BuiltInFireId,
   BuiltInMapId,
   BuiltInMixedReadonlyId,
@@ -674,7 +675,12 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
       {
         positionalParams: [],
         restParam: null,
-        returnType: {kind: 'Primitive'},
+        returnType: {
+          kind: 'Function',
+          return: {kind: 'Poly'},
+          shapeId: BuiltInFireFunctionId,
+          isConstructor: false,
+        },
         calleeEffect: Effect.Read,
         returnValueKind: ValueKind.Frozen,
       },

compiler/packages/babel-plugin-react-compiler/src/HIR/HIR.ts

@@ -746,27 +746,6 @@ export enum InstructionKind {
   Function = 'Function',
 }
 
-export function convertHoistedLValueKind(
-  kind: InstructionKind,
-): InstructionKind | null {
-  switch (kind) {
-    case InstructionKind.HoistedLet:
-      return InstructionKind.Let;
-    case InstructionKind.HoistedConst:
-      return InstructionKind.Const;
-    case InstructionKind.HoistedFunction:
-      return InstructionKind.Function;
-    case InstructionKind.Let:
-    case InstructionKind.Const:
-    case InstructionKind.Function:
-    case InstructionKind.Reassign:
-    case InstructionKind.Catch:
-      return null;
-    default:
-      assertExhaustive(kind, 'Unexpected lvalue kind');
-  }
-}
-
 function _staticInvariantInstructionValueHasLocation(
   value: InstructionValue,
 ): SourceLocation {
@@ -931,13 +910,21 @@ export type InstructionValue =
       value: Place;
       loc: SourceLocation;
     }
-  | {
+  | ({
       kind: 'TypeCastExpression';
       value: Place;
-      typeAnnotation: t.FlowType | t.TSType;
       type: Type;
       loc: SourceLocation;
-    }
+    } & (
+      | {
+          typeAnnotation: t.FlowType;
+          typeAnnotationKind: 'cast';
+        }
+      | {
+          typeAnnotation: t.TSType;
+          typeAnnotationKind: 'as' | 'satisfies';
+        }
+    ))
   | JsxExpression
   | {
       kind: 'ObjectExpression';
@@ -1735,6 +1722,12 @@ export function isDispatcherType(id: Identifier): boolean {
   return id.type.kind === 'Function' && id.type.shapeId === 'BuiltInDispatch';
 }
 
+export function isFireFunctionType(id: Identifier): boolean {
+  return (
+    id.type.kind === 'Function' && id.type.shapeId === 'BuiltInFireFunction'
+  );
+}
+
 export function isStableType(id: Identifier): boolean {
   return (
     isSetStateType(id) ||

compiler/packages/babel-plugin-react-compiler/src/HIR/MergeOverlappingReactiveScopesHIR.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {
   HIRFunction,
   InstructionId,

compiler/packages/babel-plugin-react-compiler/src/HIR/ObjectShape.ts

@@ -223,6 +223,7 @@ export const BuiltInUseContextHookId = 'BuiltInUseContextHook';
 export const BuiltInUseTransitionId = 'BuiltInUseTransition';
 export const BuiltInStartTransitionId = 'BuiltInStartTransition';
 export const BuiltInFireId = 'BuiltInFire';
+export const BuiltInFireFunctionId = 'BuiltInFireFunction';
 
 // ShapeRegistry with default definitions for built-ins.
 export const BUILTIN_SHAPES: ShapeRegistry = new Map();

compiler/packages/babel-plugin-react-compiler/src/HIR/PropagateScopeDependenciesHIR.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {
   ScopeId,
   HIRFunction,
@@ -23,9 +30,7 @@ import {
   FunctionExpression,
   ObjectMethod,
   PropertyLiteral,
-  convertHoistedLValueKind,
 } from './HIR';
-
 import {
   collectHoistablePropertyLoads,
   keyByScopeId,
@@ -466,9 +471,6 @@ class Context {
     }
     this.#reassignments.set(identifier, decl);
   }
-  hasDeclared(identifier: Identifier): boolean {
-    return this.#declarations.has(identifier.declarationId);
-  }
 
   // Checks if identifier is a valid dependency in the current scope
   #checkValidDependency(maybeDependency: ReactiveScopeDependency): boolean {
@@ -667,21 +669,21 @@ function handleInstruction(instr: Instruction, context: Context): void {
     });
   } else if (value.kind === 'DeclareLocal' || value.kind === 'DeclareContext') {
     /*
-     * Some variables may be declared and never initialized. We need to retain
-     * (and hoist) these declarations if they are included in a reactive scope.
-     * One approach is to simply add all `DeclareLocal`s as scope declarations.
-     *
-     * Context variables with hoisted declarations only become live after their
-     * first assignment. We only declare real DeclareLocal / DeclareContext
-     * instructions (not hoisted ones) to avoid generating dependencies on
-     * hoisted declarations.
+     * Some variables may be declared and never initialized. We need
+     * to retain (and hoist) these declarations if they are included
+     * in a reactive scope. One approach is to simply add all `DeclareLocal`s
+     * as scope declarations.
      */
-    if (convertHoistedLValueKind(value.lvalue.kind) === null) {
-      context.declare(value.lvalue.place.identifier, {
-        id,
-        scope: context.currentScope,
-      });
-    }
+
+    /*
+     * We add context variable declarations here, not at `StoreContext`, since
+     * context Store / Loads are modeled as reads and mutates to the underlying
+     * variable reference (instead of through intermediate / inlined temporaries)
+     */
+    context.declare(value.lvalue.place.identifier, {
+      id,
+      scope: context.currentScope,
+    });
   } else if (value.kind === 'Destructure') {
     context.visitOperand(value.value);
     for (const place of eachPatternOperand(value.lvalue.pattern)) {
@@ -693,23 +695,6 @@ function handleInstruction(instr: Instruction, context: Context): void {
         scope: context.currentScope,
       });
     }
-  } else if (value.kind === 'StoreContext') {
-    /**
-     * Some StoreContext variables have hoisted declarations. If we're storing
-     * to a context variable that hasn't yet been declared, the StoreContext is
-     * the declaration.
-     * (see corresponding logic in PruneHoistedContext)
-     */
-    if (!context.hasDeclared(value.lvalue.place.identifier)) {
-      context.declare(value.lvalue.place.identifier, {
-        id,
-        scope: context.currentScope,
-      });
-    }
-
-    for (const operand of eachInstructionValueOperand(value)) {
-      context.visitOperand(operand);
-    }
   } else {
     for (const operand of eachInstructionValueOperand(value)) {
       context.visitOperand(operand);

compiler/packages/babel-plugin-react-compiler/src/HIR/PruneUnusedLabelsHIR.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {CompilerError} from '..';
 import {BlockId, GotoVariant, HIRFunction} from './HIR';
 

compiler/packages/babel-plugin-react-compiler/src/HIR/index.ts

@@ -32,5 +32,5 @@ export {
 } from './HIRBuilder';
 export {mergeConsecutiveBlocks} from './MergeConsecutiveBlocks';
 export {mergeOverlappingReactiveScopesHIR} from './MergeOverlappingReactiveScopesHIR';
-export {printFunction, printHIR} from './PrintHIR';
+export {printFunction, printHIR, printFunctionWithOutlined} from './PrintHIR';
 export {pruneUnusedLabelsHIR} from './PruneUnusedLabelsHIR';

compiler/packages/babel-plugin-react-compiler/src/Inference/InferEffectDependencies.ts

@@ -1,3 +1,11 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import * as t from '@babel/types';
 import {CompilerError, SourceLocation} from '..';
 import {
   ArrayExpression,
@@ -17,6 +25,7 @@ import {
   ReactiveScopeDependencies,
   isUseRefType,
   isSetStateType,
+  isFireFunctionType,
 } from '../HIR';
 import {DEFAULT_EXPORT} from '../HIR/Environment';
 import {
@@ -187,11 +196,13 @@ export function inferEffectDependencies(fn: HIRFunction): void {
              * the `infer-effect-deps/pruned-nonreactive-obj` fixture for an
              * explanation.
              */
+            const usedDeps = [];
             for (const dep of scopeInfo.deps) {
               if (
-                (isUseRefType(dep.identifier) ||
+                ((isUseRefType(dep.identifier) ||
                   isSetStateType(dep.identifier)) &&
-                !reactiveIds.has(dep.identifier.id)
+                  !reactiveIds.has(dep.identifier.id)) ||
+                isFireFunctionType(dep.identifier)
               ) {
                 // exclude non-reactive hook results, which will never be in a memo block
                 continue;
@@ -205,6 +216,23 @@ export function inferEffectDependencies(fn: HIRFunction): void {
               );
               newInstructions.push(...instructions);
               effectDeps.push(place);
+              usedDeps.push(dep);
+            }
+
+            // For LSP autodeps feature.
+            const decorations: Array<t.SourceLocation> = [];
+            for (const loc of collectDepUsages(usedDeps, fnExpr.value)) {
+              if (typeof loc === 'symbol') {
+                continue;
+              }
+              decorations.push(loc);
+            }
+            if (typeof value.loc !== 'symbol') {
+              fn.env.logger?.logEvent(fn.env.filename, {
+                kind: 'AutoDepsDecorations',
+                fnLoc: value.loc,
+                decorations,
+              });
             }
 
             newInstructions.push({
@@ -217,6 +245,7 @@ export function inferEffectDependencies(fn: HIRFunction): void {
             // Step 2: push the inferred deps array as an argument of the useEffect
             value.args.push({...depsPlace, effect: Effect.Freeze});
             rewriteInstrs.set(instr.id, newInstructions);
+            fn.env.inferredEffectLocations.add(callee.loc);
           } else if (loadGlobals.has(value.args[0].identifier.id)) {
             // Global functions have no reactive dependencies, so we can insert an empty array
             newInstructions.push({
@@ -227,6 +256,32 @@ export function inferEffectDependencies(fn: HIRFunction): void {
             });
             value.args.push({...depsPlace, effect: Effect.Freeze});
             rewriteInstrs.set(instr.id, newInstructions);
+            fn.env.inferredEffectLocations.add(callee.loc);
+          }
+        } else if (
+          value.args.length >= 2 &&
+          value.args.length - 1 === autodepFnLoads.get(callee.identifier.id) &&
+          value.args[0] != null &&
+          value.args[0].kind === 'Identifier'
+        ) {
+          const penultimateArg = value.args[value.args.length - 2];
+          const depArrayArg = value.args[value.args.length - 1];
+          if (
+            depArrayArg.kind !== 'Spread' &&
+            penultimateArg.kind !== 'Spread' &&
+            typeof depArrayArg.loc !== 'symbol' &&
+            typeof penultimateArg.loc !== 'symbol' &&
+            typeof value.loc !== 'symbol'
+          ) {
+            fn.env.logger?.logEvent(fn.env.filename, {
+              kind: 'AutoDepsEligible',
+              fnLoc: value.loc,
+              depArrayLoc: {
+                ...depArrayArg.loc,
+                start: penultimateArg.loc.end,
+                end: depArrayArg.loc.end,
+              },
+            });
           }
         }
       }
@@ -336,3 +391,34 @@ function inferReactiveIdentifiers(fn: HIRFunction): Set<IdentifierId> {
   }
   return reactiveIds;
 }
+
+function collectDepUsages(
+  deps: Array<ReactiveScopeDependency>,
+  fnExpr: FunctionExpression,
+): Array<SourceLocation> {
+  const identifiers: Map<IdentifierId, ReactiveScopeDependency> = new Map();
+  const loadedDeps: Set<IdentifierId> = new Set();
+  const sourceLocations = [];
+  for (const dep of deps) {
+    identifiers.set(dep.identifier.id, dep);
+  }
+
+  for (const [, block] of fnExpr.loweredFunc.func.body.blocks) {
+    for (const instr of block.instructions) {
+      if (
+        instr.value.kind === 'LoadLocal' &&
+        identifiers.has(instr.value.place.identifier.id)
+      ) {
+        loadedDeps.add(instr.lvalue.identifier.id);
+      }
+      for (const place of eachInstructionOperand(instr)) {
+        if (loadedDeps.has(place.identifier.id)) {
+          // TODO(@jbrown215): handle member exprs!!
+          sourceLocations.push(place.identifier.loc);
+        }
+      }
+    }
+  }
+
+  return sourceLocations;
+}

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/CodegenReactiveFunction.ts

@@ -104,6 +104,7 @@ export type CodegenFunction = {
    * This is true if the compiler has compiled inferred effect dependencies
    */
   hasInferredEffect: boolean;
+  inferredEffectLocations: Set<SourceLocation>;
 
   /**
    * This is true if the compiler has compiled a fire to a useFire call
@@ -389,6 +390,7 @@ function codegenReactiveFunction(
     outlined: [],
     hasFireRewrite: fn.env.hasFireRewrite,
     hasInferredEffect: fn.env.hasInferredEffect,
+    inferredEffectLocations: fn.env.inferredEffectLocations,
   });
 }
 
@@ -2113,10 +2115,17 @@ function codegenInstructionValue(
     }
     case 'TypeCastExpression': {
       if (t.isTSType(instrValue.typeAnnotation)) {
-        value = t.tsAsExpression(
-          codegenPlaceToExpression(cx, instrValue.value),
-          instrValue.typeAnnotation,
-        );
+        if (instrValue.typeAnnotationKind === 'satisfies') {
+          value = t.tsSatisfiesExpression(
+            codegenPlaceToExpression(cx, instrValue.value),
+            instrValue.typeAnnotation,
+          );
+        } else {
+          value = t.tsAsExpression(
+            codegenPlaceToExpression(cx, instrValue.value),
+            instrValue.typeAnnotation,
+          );
+        }
       } else {
         value = t.typeCastExpression(
           codegenPlaceToExpression(cx, instrValue.value),

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/PruneHoistedContexts.ts

@@ -7,7 +7,6 @@
 
 import {CompilerError} from '..';
 import {
-  convertHoistedLValueKind,
   DeclarationId,
   InstructionKind,
   ReactiveFunction,
@@ -51,26 +50,37 @@ class Visitor extends ReactiveFunctionTransform<HoistedIdentifiers> {
     /**
      * Remove hoisted declarations to preserve TDZ
      */
-    if (instruction.value.kind === 'DeclareContext') {
-      const maybeNonHoisted = convertHoistedLValueKind(
-        instruction.value.lvalue.kind,
+    if (
+      instruction.value.kind === 'DeclareContext' &&
+      instruction.value.lvalue.kind === 'HoistedConst'
+    ) {
+      state.set(
+        instruction.value.lvalue.place.identifier.declarationId,
+        InstructionKind.Const,
       );
-      if (maybeNonHoisted != null) {
-        state.set(
-          instruction.value.lvalue.place.identifier.declarationId,
-          maybeNonHoisted,
-        );
-        return {kind: 'remove'};
-      }
-      if (instruction.value.lvalue.kind === 'Let') {
-        /**
-         * We don't expect const context variables to be hoisted
-         */
-        state.set(
-          instruction.value.lvalue.place.identifier.declarationId,
-          REWRITTEN_HOISTED_LET,
-        );
-      }
+      return {kind: 'remove'};
+    }
+
+    if (
+      instruction.value.kind === 'DeclareContext' &&
+      instruction.value.lvalue.kind === 'HoistedLet'
+    ) {
+      state.set(
+        instruction.value.lvalue.place.identifier.declarationId,
+        InstructionKind.Let,
+      );
+      return {kind: 'remove'};
+    }
+
+    if (
+      instruction.value.kind === 'DeclareContext' &&
+      instruction.value.lvalue.kind === 'HoistedFunction'
+    ) {
+      state.set(
+        instruction.value.lvalue.place.identifier.declarationId,
+        InstructionKind.Function,
+      );
+      return {kind: 'remove'};
     }
 
     if (instruction.value.kind === 'StoreContext') {

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/StabilizeBlockIds.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {
   BlockId,
   ReactiveFunction,

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/index.ts

@@ -14,7 +14,10 @@ export {extractScopeDeclarationsFromDestructuring} from './ExtractScopeDeclarati
 export {inferReactiveScopeVariables} from './InferReactiveScopeVariables';
 export {memoizeFbtAndMacroOperandsInSameScope} from './MemoizeFbtAndMacroOperandsInSameScope';
 export {mergeReactiveScopesThatInvalidateTogether} from './MergeReactiveScopesThatInvalidateTogether';
-export {printReactiveFunction} from './PrintReactiveFunction';
+export {
+  printReactiveFunction,
+  printReactiveFunctionWithOutlined,
+} from './PrintReactiveFunction';
 export {promoteUsedTemporaries} from './PromoteUsedTemporaries';
 export {propagateEarlyReturns} from './PropagateEarlyReturns';
 export {pruneAllReactiveScopes} from './PruneAllReactiveScopes';

compiler/packages/babel-plugin-react-compiler/src/Transform/TransformFire.ts

@@ -34,7 +34,11 @@ import {
 } from '../HIR';
 import {createTemporaryPlace, markInstructionIds} from '../HIR/HIRBuilder';
 import {getOrInsertWith} from '../Utils/utils';
-import {BuiltInFireId, DefaultNonmutatingHook} from '../HIR/ObjectShape';
+import {
+  BuiltInFireFunctionId,
+  BuiltInFireId,
+  DefaultNonmutatingHook,
+} from '../HIR/ObjectShape';
 import {eachInstructionOperand} from '../HIR/visitors';
 import {printSourceLocationLine} from '../HIR/PrintHIR';
 import {USE_FIRE_FUNCTION_NAME} from '../HIR/Environment';
@@ -633,6 +637,13 @@ class Context {
       () => createTemporaryPlace(this.#env, GeneratedSource),
     );
 
+    fireFunctionBinding.identifier.type = {
+      kind: 'Function',
+      shapeId: BuiltInFireFunctionId,
+      return: {kind: 'Poly'},
+      isConstructor: false,
+    };
+
     this.#capturedCalleeIdentifierIds.set(callee.identifier.id, {
       fireFunctionBinding,
       capturedCalleeIdentifier: callee.identifier,

compiler/packages/babel-plugin-react-compiler/src/Transform/index.ts

@@ -4,4 +4,5 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  */
+
 export {transformFire} from './TransformFire';

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateNoCapitalizedCalls.ts

@@ -4,6 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  */
+
 import {CompilerError, EnvironmentConfig, ErrorSeverity} from '..';
 import {HIRFunction, IdentifierId} from '../HIR';
 import {DEFAULT_GLOBALS} from '../HIR/Globals';

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/hoisted-context-variable-in-outlined-fn.expect.md

@@ -1,82 +0,0 @@
-
-## Input
-
-```javascript
-import {CONST_TRUE, useIdentity} from 'shared-runtime';
-
-const hidden = CONST_TRUE;
-function useFoo() {
-  const makeCb = useIdentity(() => {
-    const logIntervalId = () => {
-      log(intervalId);
-    };
-
-    let intervalId;
-    if (!hidden) {
-      intervalId = 2;
-    }
-    return () => {
-      logIntervalId();
-    };
-  });
-
-  return <Stringify fn={makeCb()} shouldInvokeFns={true} />;
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: useFoo,
-  params: [],
-};
-
-```
-
-## Code
-
-```javascript
-import { c as _c } from "react/compiler-runtime";
-import { CONST_TRUE, useIdentity } from "shared-runtime";
-
-const hidden = CONST_TRUE;
-function useFoo() {
-  const $ = _c(4);
-  const makeCb = useIdentity(_temp);
-  let t0;
-  if ($[0] !== makeCb) {
-    t0 = makeCb();
-    $[0] = makeCb;
-    $[1] = t0;
-  } else {
-    t0 = $[1];
-  }
-  let t1;
-  if ($[2] !== t0) {
-    t1 = <Stringify fn={t0} shouldInvokeFns={true} />;
-    $[2] = t0;
-    $[3] = t1;
-  } else {
-    t1 = $[3];
-  }
-  return t1;
-}
-function _temp() {
-  const logIntervalId = () => {
-    log(intervalId);
-  };
-  let intervalId;
-  if (!hidden) {
-    intervalId = 2;
-  }
-  return () => {
-    logIntervalId();
-  };
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: useFoo,
-  params: [],
-};
-
-```
-      
-### Eval output
-(kind: exception) Stringify is not defined

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/hoisted-context-variable-in-outlined-fn.js

@@ -1,25 +0,0 @@
-import {CONST_TRUE, useIdentity} from 'shared-runtime';
-
-const hidden = CONST_TRUE;
-function useFoo() {
-  const makeCb = useIdentity(() => {
-    const logIntervalId = () => {
-      log(intervalId);
-    };
-
-    let intervalId;
-    if (!hidden) {
-      intervalId = 2;
-    }
-    return () => {
-      logIntervalId();
-    };
-  });
-
-  return <Stringify fn={makeCb()} shouldInvokeFns={true} />;
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: useFoo,
-  params: [],
-};

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/hoisting-let-declaration-without-initialization.expect.md

@@ -1,63 +0,0 @@
-
-## Input
-
-```javascript
-import {CONST_NUMBER1, Stringify} from 'shared-runtime';
-
-function useHook({cond}) {
-  const getX = () => x;
-
-  let x;
-  if (cond) {
-    x = CONST_NUMBER1;
-  }
-  return <Stringify getX={getX} shouldInvokeFns={true} />;
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: useHook,
-  params: [{cond: true}],
-  sequentialRenders: [{cond: true}, {cond: true}, {cond: false}],
-};
-
-```
-
-## Code
-
-```javascript
-import { c as _c } from "react/compiler-runtime";
-import { CONST_NUMBER1, Stringify } from "shared-runtime";
-
-function useHook(t0) {
-  const $ = _c(2);
-  const { cond } = t0;
-  let t1;
-  if ($[0] !== cond) {
-    const getX = () => x;
-
-    let x;
-    if (cond) {
-      x = CONST_NUMBER1;
-    }
-
-    t1 = <Stringify getX={getX} shouldInvokeFns={true} />;
-    $[0] = cond;
-    $[1] = t1;
-  } else {
-    t1 = $[1];
-  }
-  return t1;
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: useHook,
-  params: [{ cond: true }],
-  sequentialRenders: [{ cond: true }, { cond: true }, { cond: false }],
-};
-
-```
-      
-### Eval output
-(kind: ok) <div>{"getX":{"kind":"Function","result":1},"shouldInvokeFns":true}</div>
-<div>{"getX":{"kind":"Function","result":1},"shouldInvokeFns":true}</div>
-<div>{"getX":{"kind":"Function"},"shouldInvokeFns":true}</div>

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/hoisting-let-declaration-without-initialization.js

@@ -1,17 +0,0 @@
-import {CONST_NUMBER1, Stringify} from 'shared-runtime';
-
-function useHook({cond}) {
-  const getX = () => x;
-
-  let x;
-  if (cond) {
-    x = CONST_NUMBER1;
-  }
-  return <Stringify getX={getX} shouldInvokeFns={true} />;
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: useHook,
-  params: [{cond: true}],
-  sequentialRenders: [{cond: true}, {cond: true}, {cond: false}],
-};

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/infer-effect-dependencies/no-emit-lint-repro.expect.md

@@ -0,0 +1,31 @@
+
+## Input
+
+```javascript
+// @inferEffectDependencies @noEmit
+import {print} from 'shared-runtime';
+import useEffectWrapper from 'useEffectWrapper';
+
+function ReactiveVariable({propVal}) {
+  const arr = [propVal];
+  useEffectWrapper(() => print(arr));
+}
+
+```
+
+## Code
+
+```javascript
+// @inferEffectDependencies @noEmit
+import { print } from "shared-runtime";
+import useEffectWrapper from "useEffectWrapper";
+
+function ReactiveVariable({ propVal }) {
+  const arr = [propVal];
+  useEffectWrapper(() => print(arr));
+}
+
+```
+      
+### Eval output
+(kind: exception) Fixture not implemented

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/infer-effect-dependencies/no-emit-lint-repro.js

@@ -0,0 +1,8 @@
+// @inferEffectDependencies @noEmit
+import {print} from 'shared-runtime';
+import useEffectWrapper from 'useEffectWrapper';
+
+function ReactiveVariable({propVal}) {
+  const arr = [propVal];
+  useEffectWrapper(() => print(arr));
+}

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/transform-fire/fire-and-autodeps.expect.md

@@ -49,7 +49,7 @@ function Component(props) {
   } else {
     t2 = $[4];
   }
-  useEffect(t2, [t1, props]);
+  useEffect(t2, [props]);
   return null;
 }
 

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/type-annotations/type-annotation-satisfies-array.expect.md

@@ -0,0 +1,71 @@
+
+## Input
+
+```javascript
+// @enableUseTypeAnnotations
+function Component(props: {id: number}) {
+  const x = makeArray(props.id) satisfies number[];
+  const y = x.at(0);
+  return y;
+}
+
+function makeArray<T>(x: T): Array<T> {
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{id: 42}],
+};
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime"; // @enableUseTypeAnnotations
+function Component(props) {
+  const $ = _c(4);
+  let t0;
+  if ($[0] !== props.id) {
+    t0 = makeArray(props.id);
+    $[0] = props.id;
+    $[1] = t0;
+  } else {
+    t0 = $[1];
+  }
+  const x = t0 satisfies number[];
+  let t1;
+  if ($[2] !== x) {
+    t1 = x.at(0);
+    $[2] = x;
+    $[3] = t1;
+  } else {
+    t1 = $[3];
+  }
+  const y = t1;
+  return y;
+}
+
+function makeArray(x) {
+  const $ = _c(2);
+  let t0;
+  if ($[0] !== x) {
+    t0 = [x];
+    $[0] = x;
+    $[1] = t0;
+  } else {
+    t0 = $[1];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ id: 42 }],
+};
+
+```
+      
+### Eval output
+(kind: ok) 42

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/type-annotations/type-annotation-satisfies-array.ts

@@ -0,0 +1,15 @@
+// @enableUseTypeAnnotations
+function Component(props: {id: number}) {
+  const x = makeArray(props.id) satisfies number[];
+  const y = x.at(0);
+  return y;
+}
+
+function makeArray<T>(x: T): Array<T> {
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{id: 42}],
+};

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/type-annotations/type-annotation-satisfies-number.expect.md

@@ -0,0 +1,41 @@
+
+## Input
+
+```javascript
+// @enableUseTypeAnnotations
+import {identity} from 'shared-runtime';
+
+function Component(props: {id: number}) {
+  const x = identity(props.id);
+  const y = x satisfies number;
+  return y;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{id: 42}],
+};
+
+```
+
+## Code
+
+```javascript
+// @enableUseTypeAnnotations
+import { identity } from "shared-runtime";
+
+function Component(props) {
+  const x = identity(props.id);
+  const y = x satisfies number;
+  return y;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ id: 42 }],
+};
+
+```
+      
+### Eval output
+(kind: ok) 42

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/type-annotations/type-annotation-satisfies-number.ts

@@ -0,0 +1,13 @@
+// @enableUseTypeAnnotations
+import {identity} from 'shared-runtime';
+
+function Component(props: {id: number}) {
+  const x = identity(props.id);
+  const y = x satisfies number;
+  return y;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{id: 42}],
+};

compiler/packages/babel-plugin-react-compiler/src/index.ts

@@ -32,13 +32,17 @@ export {
   ValueKind,
   parseConfigPragmaForTests,
   printHIR,
+  printFunctionWithOutlined,
   validateEnvironmentConfig,
   type EnvironmentConfig,
   type ExternalFunction,
   type Hook,
   type SourceLocation,
 } from './HIR';
-export {printReactiveFunction} from './ReactiveScopes';
+export {
+  printReactiveFunction,
+  printReactiveFunctionWithOutlined,
+} from './ReactiveScopes';
 declare global {
   let __DEV__: boolean | null | undefined;
 }

compiler/packages/babel-plugin-react-compiler/tsconfig.json

@@ -4,7 +4,7 @@
     "module": "ES2015",
     "moduleResolution": "Bundler",
     "rootDir": "src",
-    "outDir": "dist",
+    "noEmit": true,
     "jsx": "react-jsxdev",
     // weaken strictness from preset
     "importsNotUsedAsValues": "remove",

compiler/packages/babel-plugin-react-compiler/tsup.config.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {defineConfig} from 'tsup';
 
 export default defineConfig({

compiler/packages/eslint-plugin-react-compiler/__tests__/ReactCompilerRule-test.ts

@@ -92,36 +92,8 @@ const tests: CompilerTestCases = {
         }
       `,
     },
-    {
-      // Don't report the issue if Flow already has
-      name: '[InvalidInput] Ref access during render',
-      code: normalizeIndent`
-        function Component(props) {
-          const ref = useRef(null);
-          // $FlowFixMe[react-rule-unsafe-ref]
-          const value = ref.current;
-          return value;
-        }
-      `,
-    },
   ],
   invalid: [
-    {
-      name: '[InvalidInput] Ref access during render',
-      code: normalizeIndent`
-        function Component(props) {
-          const ref = useRef(null);
-          const value = ref.current;
-          return value;
-        }
-      `,
-      errors: [
-        {
-          message:
-            'Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef)',
-        },
-      ],
-    },
     {
       name: 'Reportable levels can be configured',
       options: [{reportableLevels: new Set([ErrorSeverity.Todo])}],

compiler/packages/eslint-plugin-react-compiler/src/rules/ReactCompilerRule.ts

@@ -105,6 +105,9 @@ const COMPILER_OPTIONS: Partial<PluginOptions> = {
   panicThreshold: 'none',
   // Don't emit errors on Flow suppressions--Flow already gave a signal
   flowSuppressions: false,
+  environment: validateEnvironmentConfig({
+    validateRefAccessDuringRender: false,
+  }),
 };
 
 const rule: Rule.RuleModule = {
@@ -149,10 +152,14 @@ const rule: Rule.RuleModule = {
     }
 
     let shouldReportUnusedOptOutDirective = true;
-    const options: PluginOptions = {
-      ...parsePluginOptions(userOpts),
+    const options: PluginOptions = parsePluginOptions({
       ...COMPILER_OPTIONS,
-    };
+      ...userOpts,
+      environment: {
+        ...COMPILER_OPTIONS.environment,
+        ...userOpts.environment,
+      },
+    });
     const userLogger: Logger | null = options.logger;
     options.logger = {
       logEvent: (filename, event): void => {

compiler/packages/eslint-plugin-react-compiler/tsup.config.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {defineConfig} from 'tsup';
 
 export default defineConfig({

compiler/packages/make-read-only-util/tsup.config.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {defineConfig} from 'tsup';
 
 export default defineConfig({

compiler/packages/react-compiler-healthcheck/src/config.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 export const config = {
   knownIncompatibleLibraries: [
     'mobx-react',

compiler/packages/react-compiler-healthcheck/tsup.config.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {defineConfig} from 'tsup';
 
 export default defineConfig({

compiler/packages/react-compiler-runtime/tsup.config.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {defineConfig} from 'tsup';
 
 export default defineConfig({

compiler/packages/react-forgive/client/src/autodeps.ts

@@ -0,0 +1,106 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import * as vscode from 'vscode';
+import {
+  LanguageClient,
+  RequestType,
+  type Position,
+} from 'vscode-languageclient/node';
+import {positionLiteralToVSCodePosition, positionsToRange} from './mapping';
+
+export type AutoDepsDecorationsLSPEvent = {
+  useEffectCallExpr: [Position, Position];
+  decorations: Array<[Position, Position]>;
+};
+
+export interface AutoDepsDecorationsParams {
+  position: Position;
+}
+
+export namespace AutoDepsDecorationsRequest {
+  export const type = new RequestType<
+    AutoDepsDecorationsParams,
+    AutoDepsDecorationsLSPEvent | null,
+    void
+  >('react/autodeps_decorations');
+}
+
+const inferredEffectDepDecoration =
+  vscode.window.createTextEditorDecorationType({
+    // TODO: make configurable?
+    borderColor: new vscode.ThemeColor('diffEditor.move.border'),
+    borderStyle: 'solid',
+    borderWidth: '0 0 4px 0',
+  });
+
+let currentlyDecoratedAutoDepFnLoc: vscode.Range | null = null;
+export function getCurrentlyDecoratedAutoDepFnLoc(): vscode.Range | null {
+  return currentlyDecoratedAutoDepFnLoc;
+}
+export function setCurrentlyDecoratedAutoDepFnLoc(range: vscode.Range): void {
+  currentlyDecoratedAutoDepFnLoc = range;
+}
+export function clearCurrentlyDecoratedAutoDepFnLoc(): void {
+  currentlyDecoratedAutoDepFnLoc = null;
+}
+
+let decorationRequestId = 0;
+export type AutoDepsDecorationsOptions = {
+  shouldUpdateCurrent: boolean;
+};
+export function requestAutoDepsDecorations(
+  client: LanguageClient,
+  position: vscode.Position,
+  options: AutoDepsDecorationsOptions,
+) {
+  const id = ++decorationRequestId;
+  client
+    .sendRequest(AutoDepsDecorationsRequest.type, {position})
+    .then(response => {
+      if (response !== null) {
+        const {
+          decorations,
+          useEffectCallExpr: [start, end],
+        } = response;
+        // Maintain ordering
+        if (decorationRequestId === id) {
+          if (options.shouldUpdateCurrent) {
+            setCurrentlyDecoratedAutoDepFnLoc(positionsToRange(start, end));
+          }
+          drawInferredEffectDepDecorations(decorations);
+        }
+      } else {
+        clearCurrentlyDecoratedAutoDepFnLoc();
+        clearDecorations(inferredEffectDepDecoration);
+      }
+    });
+}
+
+export function drawInferredEffectDepDecorations(
+  decorations: Array<[Position, Position]>,
+): void {
+  const decorationOptions = decorations.map(([start, end]) => {
+    return {
+      range: new vscode.Range(
+        positionLiteralToVSCodePosition(start),
+        positionLiteralToVSCodePosition(end),
+      ),
+      hoverMessage: 'Inferred as an effect dependency',
+    };
+  });
+  vscode.window.activeTextEditor?.setDecorations(
+    inferredEffectDepDecoration,
+    decorationOptions,
+  );
+}
+
+export function clearDecorations(
+  decorationType: vscode.TextEditorDecorationType,
+) {
+  vscode.window.activeTextEditor?.setDecorations(decorationType, []);
+}

compiler/packages/react-forgive/client/src/colors.ts

@@ -0,0 +1,80 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+type RGB = [number, number, number];
+
+const int = Math.floor;
+
+export class Color {
+  constructor(
+    private r: number,
+    private g: number,
+    private b: number,
+  ) {}
+
+  toAlphaString(a: number) {
+    return this.toCssString(a);
+  }
+  toString() {
+    return this.toCssString(1);
+  }
+
+  /**
+   * Adjust the color by a multiplier to lighten (`> 1.0`) or darken (`< 1.0`) the color. Returns a new
+   * instance.
+   */
+  adjusted(mult: number) {
+    const adjusted = Color.redistribute([
+      this.r * mult,
+      this.g * mult,
+      this.b * mult,
+    ]);
+    return new Color(...adjusted);
+  }
+
+  private toCssString(a: number) {
+    return `rgba(${this.r},${this.g},${this.b},${a})`;
+  }
+  /**
+   * Redistributes rgb, maintaing hue until its clamped.
+   * https://stackoverflow.com/a/141943
+   */
+  private static redistribute([r, g, b]: RGB): RGB {
+    const threshold = 255.999;
+    const max = Math.max(r, g, b);
+    if (max <= threshold) {
+      return [int(r), int(g), int(b)];
+    }
+    const total = r + g + b;
+    if (total >= 3 * threshold) {
+      return [int(threshold), int(threshold), int(threshold)];
+    }
+    const x = (3 * threshold - total) / (3 * max - total);
+    const gray = threshold - x * max;
+    return [int(gray + x * r), int(gray + x * g), int(gray + x * b)];
+  }
+}
+
+export const BLACK = new Color(0, 0, 0);
+export const WHITE = new Color(255, 255, 255);
+
+const COLOR_POOL = [
+  new Color(249, 65, 68),
+  new Color(243, 114, 44),
+  new Color(248, 150, 30),
+  new Color(249, 132, 74),
+  new Color(249, 199, 79),
+  new Color(144, 190, 109),
+  new Color(67, 170, 139),
+  new Color(77, 144, 142),
+  new Color(87, 117, 144),
+  new Color(39, 125, 161),
+];
+
+export function getColorFor(index: number): Color {
+  return COLOR_POOL[Math.abs(index) % COLOR_POOL.length]!;
+}

compiler/packages/react-forgive/client/src/extension.ts

@@ -1,17 +1,34 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import * as path from 'path';
-import {ExtensionContext, window as Window} from 'vscode';
+import * as vscode from 'vscode';
 
 import {
   LanguageClient,
   LanguageClientOptions,
+  type Position,
   ServerOptions,
   TransportKind,
 } from 'vscode-languageclient/node';
+import {positionLiteralToVSCodePosition} from './mapping';
+import {
+  getCurrentlyDecoratedAutoDepFnLoc,
+  requestAutoDepsDecorations,
+} from './autodeps';
 
 let client: LanguageClient;
 
-export function activate(context: ExtensionContext) {
+export function activate(context: vscode.ExtensionContext) {
   const serverModule = context.asAbsolutePath(path.join('dist', 'server.js'));
+  const documentSelector = [
+    {scheme: 'file', language: 'javascriptreact'},
+    {scheme: 'file', language: 'typescriptreact'},
+  ];
 
   // If the extension is launched in debug mode then the debug server options are used
   // Otherwise the run options are used
@@ -27,10 +44,7 @@ export function activate(context: ExtensionContext) {
   };
 
   const clientOptions: LanguageClientOptions = {
-    documentSelector: [
-      {scheme: 'file', language: 'javascriptreact'},
-      {scheme: 'file', language: 'typescriptreact'},
-    ],
+    documentSelector,
     progressOnInitialization: true,
   };
 
@@ -43,12 +57,39 @@ export function activate(context: ExtensionContext) {
       clientOptions,
     );
   } catch {
-    Window.showErrorMessage(
+    vscode.window.showErrorMessage(
       `React Analyzer couldn't be started. See the output channel for details.`,
     );
     return;
   }
 
+  vscode.languages.registerHoverProvider(documentSelector, {
+    provideHover(_document, position, _token) {
+      requestAutoDepsDecorations(client, position, {shouldUpdateCurrent: true});
+      return null;
+    },
+  });
+
+  vscode.workspace.onDidChangeTextDocument(async _e => {
+    const currentlyDecoratedAutoDepFnLoc = getCurrentlyDecoratedAutoDepFnLoc();
+    if (currentlyDecoratedAutoDepFnLoc !== null) {
+      requestAutoDepsDecorations(client, currentlyDecoratedAutoDepFnLoc.start, {
+        shouldUpdateCurrent: false,
+      });
+    }
+  });
+
+  vscode.commands.registerCommand(
+    'react.requestAutoDepsDecorations',
+    (position: Position) => {
+      requestAutoDepsDecorations(
+        client,
+        positionLiteralToVSCodePosition(position),
+        {shouldUpdateCurrent: true},
+      );
+    },
+  );
+
   client.registerProposedFeatures();
   client.start();
 }
@@ -57,4 +98,5 @@ export function deactivate(): Thenable<void> | undefined {
   if (client !== undefined) {
     return client.stop();
   }
+  return;
 }

compiler/packages/react-forgive/client/src/mapping.ts

@@ -0,0 +1,22 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import * as vscode from 'vscode';
+import {Position} from 'vscode-languageclient/node';
+
+export function positionLiteralToVSCodePosition(
+  position: Position,
+): vscode.Position {
+  return new vscode.Position(position.line, position.character);
+}
+
+export function positionsToRange(start: Position, end: Position): vscode.Range {
+  return new vscode.Range(
+    positionLiteralToVSCodePosition(start),
+    positionLiteralToVSCodePosition(end),
+  );
+}

compiler/packages/react-forgive/server/src/compiler/compat.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {SourceLocation} from 'babel-plugin-react-compiler/src';
 import {type Range} from 'vscode-languageserver';
 

compiler/packages/react-forgive/server/src/compiler/index.ts

@@ -33,6 +33,8 @@ export async function compile({
       plugins: ['typescript', 'jsx'],
     },
     sourceType: 'module',
+    configFile: false,
+    babelrc: false,
   });
   if (ast == null) {
     return null;
@@ -48,6 +50,8 @@ export async function compile({
     plugins,
     sourceType: 'module',
     sourceFileName: file,
+    configFile: false,
+    babelrc: false,
   });
   if (result?.code == null) {
     throw new Error(

compiler/packages/react-forgive/server/src/index.ts

@@ -7,10 +7,14 @@
 
 import {TextDocument} from 'vscode-languageserver-textdocument';
 import {
+  CodeAction,
+  CodeActionKind,
   CodeLens,
+  Command,
   createConnection,
   type InitializeParams,
   type InitializeResult,
+  Position,
   ProposedFeatures,
   TextDocuments,
   TextDocumentSyncKind,
@@ -19,11 +23,22 @@ import {compile, lastResult} from './compiler';
 import {type PluginOptions} from 'babel-plugin-react-compiler/src';
 import {resolveReactConfig} from './compiler/options';
 import {
-  CompileSuccessEvent,
+  type CompileSuccessEvent,
+  type LoggerEvent,
   defaultOptions,
-  LoggerEvent,
 } from 'babel-plugin-react-compiler/src/Entrypoint/Options';
 import {babelLocationToRange, getRangeFirstCharacter} from './compiler/compat';
+import {
+  type AutoDepsDecorationsLSPEvent,
+  AutoDepsDecorationsRequest,
+  mapCompilerEventToLSPEvent,
+} from './requests/autodepsdecorations';
+import {
+  isPositionWithinRange,
+  isRangeWithinRange,
+  Range,
+  sourceLocationToRange,
+} from './utils/range';
 
 const SUPPORTED_LANGUAGE_IDS = new Set([
   'javascript',
@@ -37,17 +52,68 @@ const documents = new TextDocuments(TextDocument);
 
 let compilerOptions: PluginOptions | null = null;
 let compiledFns: Set<CompileSuccessEvent> = new Set();
+let autoDepsDecorations: Array<AutoDepsDecorationsLSPEvent> = [];
+let codeActionEvents: Array<CodeActionLSPEvent> = [];
+
+type CodeActionLSPEvent = {
+  title: string;
+  kind: CodeActionKind;
+  newText: string;
+  anchorRange: Range;
+  editRange: {start: Position; end: Position};
+};
 
 connection.onInitialize((_params: InitializeParams) => {
   // TODO(@poteto) get config fr
   compilerOptions = resolveReactConfig('.') ?? defaultOptions;
   compilerOptions = {
     ...compilerOptions,
+    environment: {
+      ...compilerOptions.environment,
+      inferEffectDependencies: [
+        {
+          function: {
+            importSpecifierName: 'useEffect',
+            source: 'react',
+          },
+          numRequiredArgs: 1,
+        },
+        {
+          function: {
+            importSpecifierName: 'useSpecialEffect',
+            source: 'shared-runtime',
+          },
+          numRequiredArgs: 2,
+        },
+        {
+          function: {
+            importSpecifierName: 'default',
+            source: 'useEffectWrapper',
+          },
+          numRequiredArgs: 1,
+        },
+      ],
+    },
     logger: {
       logEvent(_filename: string | null, event: LoggerEvent) {
+        connection.console.info(`Received event: ${event.kind}`);
+        connection.console.debug(JSON.stringify(event, null, 2));
         if (event.kind === 'CompileSuccess') {
           compiledFns.add(event);
         }
+        if (event.kind === 'AutoDepsDecorations') {
+          autoDepsDecorations.push(mapCompilerEventToLSPEvent(event));
+        }
+        if (event.kind === 'AutoDepsEligible') {
+          const depArrayLoc = sourceLocationToRange(event.depArrayLoc);
+          codeActionEvents.push({
+            title: 'Use React Compiler inferred dependency array',
+            kind: CodeActionKind.QuickFix,
+            newText: '',
+            anchorRange: sourceLocationToRange(event.fnLoc),
+            editRange: {start: depArrayLoc[0], end: depArrayLoc[1]},
+          });
+        }
       },
     },
   };
@@ -55,6 +121,7 @@ connection.onInitialize((_params: InitializeParams) => {
     capabilities: {
       textDocumentSync: TextDocumentSyncKind.Full,
       codeLensProvider: {resolveProvider: true},
+      codeActionProvider: {resolveProvider: true},
     },
   };
   return result;
@@ -65,20 +132,29 @@ connection.onInitialized(() => {
 });
 
 documents.onDidChangeContent(async event => {
-  connection.console.info(`Changed: ${event.document.uri}`);
-  compiledFns.clear();
+  connection.console.info(`Compiling: ${event.document.uri}`);
+  resetState();
   if (SUPPORTED_LANGUAGE_IDS.has(event.document.languageId)) {
     const text = event.document.getText();
-    await compile({
-      text,
-      file: event.document.uri,
-      options: compilerOptions,
-    });
+    try {
+      await compile({
+        text,
+        file: event.document.uri,
+        options: compilerOptions,
+      });
+    } catch (err) {
+      connection.console.error('Failed to compile');
+      if (err instanceof Error) {
+        connection.console.error(err.stack ?? err.message);
+      } else {
+        connection.console.error(JSON.stringify(err, null, 2));
+      }
+    }
   }
 });
 
 connection.onDidChangeWatchedFiles(change => {
-  compiledFns.clear();
+  resetState();
   connection.console.log(
     change.changes.map(c => `File changed: ${c.uri}`).join('\n'),
   );
@@ -118,6 +194,62 @@ connection.onCodeLensResolve(lens => {
   return lens;
 });
 
+connection.onCodeAction(params => {
+  const codeActions: Array<CodeAction> = [];
+  for (const codeActionEvent of codeActionEvents) {
+    if (
+      isRangeWithinRange(
+        [params.range.start, params.range.end],
+        codeActionEvent.anchorRange,
+      )
+    ) {
+      const codeAction = CodeAction.create(
+        codeActionEvent.title,
+        {
+          changes: {
+            [params.textDocument.uri]: [
+              {
+                newText: codeActionEvent.newText,
+                range: codeActionEvent.editRange,
+              },
+            ],
+          },
+        },
+        codeActionEvent.kind,
+      );
+      // After executing a codeaction, we want to draw autodep decorations again
+      codeAction.command = Command.create(
+        'Request autodeps decorations',
+        'react.requestAutoDepsDecorations',
+        codeActionEvent.anchorRange[0],
+      );
+      codeActions.push(codeAction);
+    }
+  }
+  return codeActions;
+});
+
+/**
+ * The client can request the server to compute autodeps decorations based on a currently selected
+ * position if the selected position is within an autodep eligible function call.
+ */
+connection.onRequest(AutoDepsDecorationsRequest.type, async params => {
+  const position = params.position;
+  for (const decoration of autoDepsDecorations) {
+    if (isPositionWithinRange(position, decoration.useEffectCallExpr)) {
+      return decoration;
+    }
+  }
+  return null;
+});
+
+function resetState() {
+  connection.console.debug('Clearing state');
+  compiledFns.clear();
+  autoDepsDecorations = [];
+  codeActionEvents = [];
+}
+
 documents.listen(connection);
 connection.listen();
 connection.console.info(`React Analyzer running in node ${process.version}`);

compiler/packages/react-forgive/server/src/requests/autodepsdecorations.ts

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {type AutoDepsDecorationsEvent} from 'babel-plugin-react-compiler/src/Entrypoint';
+import {type Position} from 'vscode-languageserver-textdocument';
+import {RequestType} from 'vscode-languageserver/node';
+import {type Range, sourceLocationToRange} from '../utils/range';
+
+export type AutoDepsDecorationsLSPEvent = {
+  useEffectCallExpr: Range;
+  decorations: Array<Range>;
+};
+export interface AutoDepsDecorationsParams {
+  position: Position;
+}
+export namespace AutoDepsDecorationsRequest {
+  export const type = new RequestType<
+    AutoDepsDecorationsParams,
+    AutoDepsDecorationsLSPEvent,
+    void
+  >('react/autodeps_decorations');
+}
+
+export function mapCompilerEventToLSPEvent(
+  event: AutoDepsDecorationsEvent,
+): AutoDepsDecorationsLSPEvent {
+  return {
+    useEffectCallExpr: sourceLocationToRange(event.fnLoc),
+    decorations: event.decorations.map(sourceLocationToRange),
+  };
+}

compiler/packages/react-forgive/server/src/utils/range.ts

@@ -0,0 +1,42 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import * as t from '@babel/types';
+import {type Position} from 'vscode-languageserver/node';
+
+export type Range = [Position, Position];
+
+export function isPositionWithinRange(
+  position: Position,
+  [start, end]: Range,
+): boolean {
+  return position.line >= start.line && position.line <= end.line;
+}
+
+export function isRangeWithinRange(aRange: Range, bRange: Range): boolean {
+  const startComparison = comparePositions(aRange[0], bRange[0]);
+  const endComparison = comparePositions(aRange[1], bRange[1]);
+  return startComparison >= 0 && endComparison <= 0;
+}
+
+function comparePositions(a: Position, b: Position): number {
+  const lineComparison = a.line - b.line;
+  if (lineComparison === 0) {
+    return a.character - b.character;
+  } else {
+    return lineComparison;
+  }
+}
+
+export function sourceLocationToRange(
+  loc: t.SourceLocation,
+): [Position, Position] {
+  return [
+    {line: loc.start.line - 1, character: loc.start.column},
+    {line: loc.end.line - 1, character: loc.end.column},
+  ];
+}

compiler/packages/react-forgive/tsconfig.json

@@ -0,0 +1,16 @@
+{
+  "extends": "@tsconfig/strictest/tsconfig.json",
+  "compilerOptions": {
+    "module": "Node16",
+    "moduleResolution": "Node16",
+    "rootDir": "../",
+    "noEmit": true,
+    "jsx": "react-jsxdev",
+    "lib": ["ES2022"],
+
+    "target": "ES2022",
+    "importsNotUsedAsValues": "remove",
+  },
+  "exclude": ["node_modules"],
+  "include": ["server/src/**/*.ts", "client/src/**/*.ts"],
+}

compiler/packages/react-mcp-server/README.md

@@ -0,0 +1,22 @@
+# React MCP Server (experimental)
+
+An experimental MCP Server for React.
+
+## Development
+
+First, add this file if you're using Claude Desktop: `code ~/Library/Application\ Support/Claude/claude_desktop_config.json`. Copy the absolute path from `which node` and from `react/compiler/react-mcp-server/dist/index.js` and paste, for example:
+
+```json
+{
+  "mcpServers": {
+    "react": {
+      "command": "/Users/<username>/.asdf/shims/node",
+      "args": [
+        "/Users/<username>/code/react/compiler/packages/react-mcp-server/dist/index.js"
+      ]
+    }
+  }
+}
+```
+
+Next, run `yarn workspace react-mcp-server watch` from the `react/compiler` directory and make changes as needed. You will need to restart Claude everytime you want to try your changes.

compiler/packages/react-mcp-server/package.json

@@ -0,0 +1,35 @@
+{
+  "name": "react-mcp-server",
+  "version": "0.0.0",
+  "description": "React MCP Server (experimental)",
+  "bin": {
+    "react-mcp-server": "./dist/index.js"
+  },
+  "scripts": {
+    "build": "rimraf dist && tsup",
+    "test": "echo 'no tests'",
+    "dev": "concurrently --kill-others -n build,inspect \"yarn run watch\" \"wait-on dist/index.js && yarn run inspect\"",
+    "inspect": "npx @modelcontextprotocol/inspector node dist/index.js",
+    "watch": "yarn build --watch"
+  },
+  "dependencies": {
+    "@babel/core": "^7.26.0",
+    "@babel/parser": "^7.26",
+    "@babel/plugin-syntax-typescript": "^7.25.9",
+    "@modelcontextprotocol/sdk": "^1.9.0",
+    "algoliasearch": "^5.23.3",
+    "cheerio": "^1.0.0",
+    "html-to-text": "^9.0.5",
+    "prettier": "^3.3.3",
+    "zod": "^3.23.8"
+  },
+  "devDependencies": {
+    "@types/html-to-text": "^9.0.4"
+  },
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/facebook/react.git",
+    "directory": "compiler/packages/react-mcp-server"
+  }
+}

compiler/packages/react-mcp-server/src/compiler/index.ts

@@ -0,0 +1,77 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import type * as BabelCore from '@babel/core';
+import {parseAsync, transformFromAstAsync} from '@babel/core';
+import BabelPluginReactCompiler, {
+  type PluginOptions,
+} from 'babel-plugin-react-compiler/src';
+import * as prettier from 'prettier';
+
+export let lastResult: BabelCore.BabelFileResult | null = null;
+
+export type PrintedCompilerPipelineValue =
+  | {
+      kind: 'hir';
+      name: string;
+      fnName: string | null;
+      value: string;
+    }
+  | {kind: 'reactive'; name: string; fnName: string | null; value: string}
+  | {kind: 'debug'; name: string; fnName: string | null; value: string};
+
+type CompileOptions = {
+  text: string;
+  file: string;
+  options: Partial<PluginOptions> | null;
+};
+export async function compile({
+  text,
+  file,
+  options,
+}: CompileOptions): Promise<BabelCore.BabelFileResult> {
+  const ast = await parseAsync(text, {
+    sourceFileName: file,
+    parserOpts: {
+      plugins: ['typescript', 'jsx'],
+    },
+    sourceType: 'module',
+  });
+  if (ast == null) {
+    throw new Error('Could not parse');
+  }
+  const plugins =
+    options != null
+      ? [[BabelPluginReactCompiler, options]]
+      : [[BabelPluginReactCompiler]];
+  const result = await transformFromAstAsync(ast, text, {
+    filename: file,
+    highlightCode: false,
+    retainLines: true,
+    plugins,
+    sourceType: 'module',
+    sourceFileName: file,
+  });
+  if (result?.code == null) {
+    throw new Error(
+      `Expected BabelPluginReactCompiler to compile successfully, got ${result}`,
+    );
+  }
+  try {
+    result.code = await prettier.format(result.code, {
+      semi: false,
+      parser: 'babel-ts',
+    });
+    if (result.code != null) {
+      lastResult = result;
+    }
+  } catch (err) {
+    // If prettier failed just log, no need to crash
+    console.error(err);
+  }
+  return result;
+}

compiler/packages/react-mcp-server/src/index.ts

@@ -0,0 +1,365 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {McpServer} from '@modelcontextprotocol/sdk/server/mcp.js';
+import {StdioServerTransport} from '@modelcontextprotocol/sdk/server/stdio.js';
+import {z} from 'zod';
+import {compile, type PrintedCompilerPipelineValue} from './compiler';
+import {
+  CompilerPipelineValue,
+  printReactiveFunctionWithOutlined,
+  printFunctionWithOutlined,
+  PluginOptions,
+  SourceLocation,
+} from 'babel-plugin-react-compiler/src';
+import * as cheerio from 'cheerio';
+import {queryAlgolia} from './utils/algolia';
+import assertExhaustive from './utils/assertExhaustive';
+import {convert} from 'html-to-text';
+
+const server = new McpServer({
+  name: 'React',
+  version: '0.0.0',
+});
+
+server.tool(
+  'query-react-dev-docs',
+  'Search/look up official docs from react.dev',
+  {
+    query: z.string(),
+  },
+  async ({query}) => {
+    try {
+      const pages = await queryAlgolia(query);
+      if (pages.length === 0) {
+        return {
+          content: [{type: 'text' as const, text: `No results`}],
+        };
+      }
+      const content = pages.map(html => {
+        const $ = cheerio.load(html);
+        // react.dev should always have at least one <article> with the main content
+        const article = $('article').html();
+        if (article != null) {
+          return {
+            type: 'text' as const,
+            text: convert(article),
+          };
+        } else {
+          return {
+            type: 'text' as const,
+            // Fallback to converting the whole page to text.
+            text: convert($.html()),
+          };
+        }
+      });
+      return {
+        content,
+      };
+    } catch (err) {
+      return {
+        isError: true,
+        content: [{type: 'text' as const, text: `Error: ${err.stack}`}],
+      };
+    }
+  },
+);
+
+server.tool(
+  'compile',
+  'Compile code with React Compiler. Optionally, for debugging provide a pass name like "HIR" to see more information.',
+  {
+    text: z.string(),
+    passName: z.enum(['HIR', 'ReactiveFunction', 'All', '@DEBUG']).optional(),
+  },
+  async ({text, passName}) => {
+    const pipelinePasses = new Map<
+      string,
+      Array<PrintedCompilerPipelineValue>
+    >();
+    const recordPass: (
+      result: PrintedCompilerPipelineValue,
+    ) => void = result => {
+      const entry = pipelinePasses.get(result.name);
+      if (Array.isArray(entry)) {
+        entry.push(result);
+      } else {
+        pipelinePasses.set(result.name, [result]);
+      }
+    };
+    const logIR = (result: CompilerPipelineValue): void => {
+      switch (result.kind) {
+        case 'ast': {
+          break;
+        }
+        case 'hir': {
+          recordPass({
+            kind: 'hir',
+            fnName: result.value.id,
+            name: result.name,
+            value: printFunctionWithOutlined(result.value),
+          });
+          break;
+        }
+        case 'reactive': {
+          recordPass({
+            kind: 'reactive',
+            fnName: result.value.id,
+            name: result.name,
+            value: printReactiveFunctionWithOutlined(result.value),
+          });
+          break;
+        }
+        case 'debug': {
+          recordPass({
+            kind: 'debug',
+            fnName: null,
+            name: result.name,
+            value: result.value,
+          });
+          break;
+        }
+        default: {
+          assertExhaustive(result, `Unhandled result ${result}`);
+        }
+      }
+    };
+    const errors: Array<{message: string; loc: SourceLocation | null}> = [];
+    const compilerOptions: Partial<PluginOptions> = {
+      panicThreshold: 'none',
+      logger: {
+        debugLogIRs: logIR,
+        logEvent: (_filename, event): void => {
+          if (event.kind === 'CompileError') {
+            const detail = event.detail;
+            const loc =
+              detail.loc == null || typeof detail.loc == 'symbol'
+                ? event.fnLoc
+                : detail.loc;
+            errors.push({
+              message: detail.reason,
+              loc,
+            });
+          }
+        },
+      },
+    };
+    try {
+      const result = await compile({
+        text,
+        file: 'anonymous.tsx',
+        options: compilerOptions,
+      });
+      if (result.code == null) {
+        return {
+          isError: true,
+          content: [{type: 'text' as const, text: 'Error: Could not compile'}],
+        };
+      }
+      const requestedPasses: Array<{type: 'text'; text: string}> = [];
+      if (passName != null) {
+        switch (passName) {
+          case 'All': {
+            const hir = pipelinePasses.get('PropagateScopeDependenciesHIR');
+            if (hir !== undefined) {
+              for (const pipelineValue of hir) {
+                requestedPasses.push({
+                  type: 'text' as const,
+                  text: pipelineValue.value,
+                });
+              }
+            }
+            const reactiveFunc = pipelinePasses.get('PruneHoistedContexts');
+            if (reactiveFunc !== undefined) {
+              for (const pipelineValue of reactiveFunc) {
+                requestedPasses.push({
+                  type: 'text' as const,
+                  text: pipelineValue.value,
+                });
+              }
+            }
+            break;
+          }
+          case 'HIR': {
+            // Last pass before HIR -> ReactiveFunction
+            const requestedPass = pipelinePasses.get(
+              'PropagateScopeDependenciesHIR',
+            );
+            if (requestedPass !== undefined) {
+              for (const pipelineValue of requestedPass) {
+                requestedPasses.push({
+                  type: 'text' as const,
+                  text: pipelineValue.value,
+                });
+              }
+            } else {
+              console.error(`Could not find requested pass ${passName}`);
+            }
+            break;
+          }
+          case 'ReactiveFunction': {
+            // Last pass
+            const requestedPass = pipelinePasses.get('PruneHoistedContexts');
+            if (requestedPass !== undefined) {
+              for (const pipelineValue of requestedPass) {
+                requestedPasses.push({
+                  type: 'text' as const,
+                  text: pipelineValue.value,
+                });
+              }
+            } else {
+              console.error(`Could not find requested pass ${passName}`);
+            }
+            break;
+          }
+          case '@DEBUG': {
+            for (const [, pipelinePass] of pipelinePasses) {
+              for (const pass of pipelinePass) {
+                requestedPasses.push({
+                  type: 'text' as const,
+                  text: `${pass.name}\n\n${pass.value}`,
+                });
+              }
+            }
+            break;
+          }
+          default: {
+            assertExhaustive(
+              passName,
+              `Unhandled passName option: ${passName}`,
+            );
+          }
+        }
+        const requestedPass = pipelinePasses.get(passName);
+        if (requestedPass !== undefined) {
+          for (const pipelineValue of requestedPass) {
+            if (pipelineValue.name === passName) {
+              requestedPasses.push({
+                type: 'text' as const,
+                text: pipelineValue.value,
+              });
+            }
+          }
+        }
+      }
+      if (errors.length > 0) {
+        return {
+          content: errors.map(err => {
+            return {
+              type: 'text' as const,
+              text:
+                err.loc === null || typeof err.loc === 'symbol'
+                  ? `React Compiler bailed out:\n\n${err.message}`
+                  : `React Compiler bailed out:\n\n${err.message}@${err.loc.start.line}:${err.loc.end.line}`,
+            };
+          }),
+        };
+      }
+      return {
+        content: [
+          {type: 'text' as const, text: result.code},
+          ...requestedPasses,
+        ],
+      };
+    } catch (err) {
+      return {
+        isError: true,
+        content: [{type: 'text' as const, text: `Error: ${err.stack}`}],
+      };
+    }
+  },
+);
+
+server.prompt('review-react-code', () => ({
+  messages: [
+    {
+      role: 'assistant',
+      content: {
+        type: 'text',
+        text: `
+## Role
+You are a React assistant that helps users write more efficient and optimizable React code. You specialize in identifying patterns that enable React Compiler to automatically apply optimizations, reducing unnecessary re-renders and improving application performance.
+
+## Follow these guidelines in all code you produce and suggest
+Use functional components with Hooks: Do not generate class components or use old lifecycle methods. Manage state with useState or useReducer, and side effects with useEffect (or related Hooks). Always prefer functions and Hooks for any new component logic.
+
+Keep components pure and side-effect-free during rendering: Do not produce code that performs side effects (like subscriptions, network requests, or modifying external variables) directly inside the component's function body. Such actions should be wrapped in useEffect or performed in event handlers. Ensure your render logic is a pure function of props and state.
+
+Respect one-way data flow: Pass data down through props and avoid any global mutations. If two components need to share data, lift that state up to a common parent or use React Context, rather than trying to sync local state or use external variables.
+
+Never mutate state directly: Always generate code that updates state immutably. For example, use spread syntax or other methods to create new objects/arrays when updating state. Do not use assignments like state.someValue = ... or array mutations like array.push() on state variables. Use the state setter (setState from useState, etc.) to update state.
+
+Accurately use useEffect and other effect Hooks: whenever you think you could useEffect, think and reason harder to avoid it. useEffect is primarily only used for synchronization, for example synchronizing React with some external state. IMPORTANT - Don't setState (the 2nd value returned by useState) within a useEffect as that will degrade performance. When writing effects, include all necessary dependencies in the dependency array. Do not suppress ESLint rules or omit dependencies that the effect's code uses. Structure the effect callbacks to handle changing values properly (e.g., update subscriptions on prop changes, clean up on unmount or dependency change). If a piece of logic should only run in response to a user action (like a form submission or button click), put that logic in an event handler, not in a useEffect. Where possible, useEffects should return a cleanup function.
+
+Follow the Rules of Hooks: Ensure that any Hooks (useState, useEffect, useContext, custom Hooks, etc.) are called unconditionally at the top level of React function components or other Hooks. Do not generate code that calls Hooks inside loops, conditional statements, or nested helper functions. Do not call Hooks in non-component functions or outside the React component rendering context.
+
+Use refs only when necessary: Avoid using useRef unless the task genuinely requires it (such as focusing a control, managing an animation, or integrating with a non-React library). Do not use refs to store application state that should be reactive. If you do use refs, never write to or read from ref.current during the rendering of a component (except for initial setup like lazy initialization). Any ref usage should not affect the rendered output directly.
+
+Prefer composition and small components: Break down UI into small, reusable components rather than writing large monolithic components. The code you generate should promote clarity and reusability by composing components together. Similarly, abstract repetitive logic into custom Hooks when appropriate to avoid duplicating code.
+
+Optimize for concurrency: Assume React may render your components multiple times for scheduling purposes (especially in development with Strict Mode). Write code that remains correct even if the component function runs more than once. For instance, avoid side effects in the component body and use functional state updates (e.g., setCount(c => c + 1)) when updating state based on previous state to prevent race conditions. Always include cleanup functions in effects that subscribe to external resources. Don't write useEffects for "do this when this changes" side-effects. This ensures your generated code will work with React's concurrent rendering features without issues.
+
+Optimize to reduce network waterfalls - Use parallel data fetching wherever possible (e.g., start multiple requests at once rather than one after another). Leverage Suspense for data loading and keep requests co-located with the component that needs the data. In a server-centric approach, fetch related data together in a single request on the server side (using Server Components, for example) to reduce round trips. Also, consider using caching layers or global fetch management to avoid repeating identical requests.
+
+Rely on React Compiler - useMemo, useCallback, and React.memo can be omitted if React Compiler is enabled. Avoid premature optimization with manual memoization. Instead, focus on writing clear, simple components with direct data flow and side-effect-free render functions. Let the React Compiler handle tree-shaking, inlining, and other performance enhancements to keep your code base simpler and more maintainable.
+
+Design for a good user experience - Provide clear, minimal, and non-blocking UI states. When data is loading, show lightweight placeholders (e.g., skeleton screens) rather than intrusive spinners everywhere. Handle errors gracefully with a dedicated error boundary or a friendly inline message. Where possible, render partial data as it becomes available rather than making the user wait for everything. Suspense allows you to declare the loading states in your component tree in a natural way, preventing “flash” states and improving perceived performance.
+
+Server Components - Shift data-heavy logic to the server whenever possible. Break up the more static parts of the app into server components. Break up data fetching into server components. Only client components (denoted by the 'use client' top level directive) need interactivity. By rendering parts of your UI on the server, you reduce the client-side JavaScript needed and avoid sending unnecessary data over the wire. Use Server Components to prefetch and pre-render data, allowing faster initial loads and smaller bundle sizes. This also helps manage or eliminate certain waterfalls by resolving data on the server before streaming the HTML (and partial React tree) to the client.
+
+## Available Tools
+- 'docs': Look up documentation from react.dev. Returns text as a string.
+- 'compile': Run the user's code through React Compiler. Returns optimized JS/TS code with potential diagnostics.
+
+## Process
+1. Analyze the user's code for optimization opportunities:
+   - Check for React anti-patterns that prevent compiler optimization
+   - Identify unnecessary manual optimizations (useMemo, useCallback, React.memo) that the compiler can handle
+   - Look for component structure issues that limit compiler effectiveness
+   - Think about each suggestion you are making and consult React docs using the docs://{query} resource for best practices
+
+2. Use React Compiler to verify optimization potential:
+   - Run the code through the compiler and analyze the output
+   - You can run the compiler multiple times to verify your work
+   - Check for successful optimization by looking for const $ = _c(n) cache entries, where n is an integer
+   - Identify bailout messages that indicate where code could be improved
+   - Compare before/after optimization potential
+
+3. Provide actionable guidance:
+   - Explain specific code changes with clear reasoning
+   - Show before/after examples when suggesting changes
+   - Include compiler results to demonstrate the impact of optimizations
+   - Only suggest changes that meaningfully improve optimization potential
+
+## Optimization Guidelines
+- Avoid mutation of values that are memoized by the compiler
+- State updates should be structured to enable granular updates
+- Side effects should be isolated and dependencies clearly defined
+- The compiler automatically inserts memoization, so manually added useMemo/useCallback/React.memo can often be removed
+
+## Understanding Compiler Output
+- Successful optimization adds import { c as _c } from "react/compiler-runtime";
+- Successful optimization initializes a constant sized cache with const $ = _c(n), where n is the size of the cache as an integer
+- When suggesting changes, try to increase or decrease the number of cached expressions (visible in const $ = _c(n))
+  - Increase: more memoization coverage
+  - Decrease: if there are unnecessary dependencies, less dependencies mean less re-rendering
+`,
+      },
+    },
+  ],
+}));
+
+async function main() {
+  const transport = new StdioServerTransport();
+  await server.connect(transport);
+  console.error('React Compiler MCP Server running on stdio');
+}
+
+main().catch(error => {
+  console.error('Fatal error in main():', error);
+  process.exit(1);
+});

compiler/packages/react-mcp-server/src/types/algolia.ts

@@ -0,0 +1,100 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// https://github.com/algolia/docsearch/blob/15ebcba606b281aa0dddc4ccb8feb19d396bf79e/packages/docsearch-react/src/types/DocSearchHit.ts
+type ContentType =
+  | 'content'
+  | 'lvl0'
+  | 'lvl1'
+  | 'lvl2'
+  | 'lvl3'
+  | 'lvl4'
+  | 'lvl5'
+  | 'lvl6';
+
+interface DocSearchHitAttributeHighlightResult {
+  value: string;
+  matchLevel: 'full' | 'none' | 'partial';
+  matchedWords: string[];
+  fullyHighlighted?: boolean;
+}
+
+interface DocSearchHitHighlightResultHierarchy {
+  lvl0: DocSearchHitAttributeHighlightResult;
+  lvl1: DocSearchHitAttributeHighlightResult;
+  lvl2: DocSearchHitAttributeHighlightResult;
+  lvl3: DocSearchHitAttributeHighlightResult;
+  lvl4: DocSearchHitAttributeHighlightResult;
+  lvl5: DocSearchHitAttributeHighlightResult;
+  lvl6: DocSearchHitAttributeHighlightResult;
+}
+
+interface DocSearchHitHighlightResult {
+  content: DocSearchHitAttributeHighlightResult;
+  hierarchy: DocSearchHitHighlightResultHierarchy;
+  hierarchy_camel: DocSearchHitHighlightResultHierarchy[];
+}
+
+interface DocSearchHitAttributeSnippetResult {
+  value: string;
+  matchLevel: 'full' | 'none' | 'partial';
+}
+
+interface DocSearchHitSnippetResult {
+  content: DocSearchHitAttributeSnippetResult;
+  hierarchy: DocSearchHitHighlightResultHierarchy;
+  hierarchy_camel: DocSearchHitHighlightResultHierarchy[];
+}
+
+export declare type DocSearchHit = {
+  objectID: string;
+  content: string | null;
+  url: string;
+  url_without_anchor: string;
+  type: ContentType;
+  anchor: string | null;
+  hierarchy: {
+    lvl0: string;
+    lvl1: string;
+    lvl2: string | null;
+    lvl3: string | null;
+    lvl4: string | null;
+    lvl5: string | null;
+    lvl6: string | null;
+  };
+  _highlightResult: DocSearchHitHighlightResult;
+  _snippetResult: DocSearchHitSnippetResult;
+  _rankingInfo?: {
+    promoted: boolean;
+    nbTypos: number;
+    firstMatchedWord: number;
+    proximityDistance?: number;
+    geoDistance: number;
+    geoPrecision?: number;
+    nbExactWords: number;
+    words: number;
+    filters: number;
+    userScore: number;
+    matchedGeoLocation?: {
+      lat: number;
+      lng: number;
+      distance: number;
+    };
+  };
+  _distinctSeqID?: number;
+  __autocomplete_indexName?: string;
+  __autocomplete_queryID?: string;
+  __autocomplete_algoliaCredentials?: {
+    appId: string;
+    apiKey: string;
+  };
+  __autocomplete_id?: number;
+};
+
+export type InternalDocSearchHit = DocSearchHit & {
+  __docsearch_parent: InternalDocSearchHit | null;
+};

compiler/packages/react-mcp-server/src/utils/algolia.ts

@@ -0,0 +1,119 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import type {DocSearchHit, InternalDocSearchHit} from '../types/algolia';
+import {liteClient, type Hit, type SearchResponse} from 'algoliasearch/lite';
+
+// https://github.com/reactjs/react.dev/blob/55986965fbf69c2584040039c9586a01bd54eba7/src/siteConfig.js#L15-L19
+const ALGOLIA_CONFIG = {
+  appId: '1FCF9AYYAT',
+  apiKey: '1b7ad4e1c89e645e351e59d40544eda1',
+  indexName: 'beta-react',
+};
+
+export const ALGOLIA_CLIENT = liteClient(
+  ALGOLIA_CONFIG.appId,
+  ALGOLIA_CONFIG.apiKey,
+);
+
+export function printHierarchy(
+  hit: DocSearchHit | InternalDocSearchHit,
+): string {
+  let val = `${hit.hierarchy.lvl0} > ${hit.hierarchy.lvl1}`;
+  if (hit.hierarchy.lvl2 != null) {
+    val = val.concat(` > ${hit.hierarchy.lvl2}`);
+  }
+  if (hit.hierarchy.lvl3 != null) {
+    val = val.concat(` > ${hit.hierarchy.lvl3}`);
+  }
+  if (hit.hierarchy.lvl4 != null) {
+    val = val.concat(` > ${hit.hierarchy.lvl4}`);
+  }
+  if (hit.hierarchy.lvl5 != null) {
+    val = val.concat(` > ${hit.hierarchy.lvl5}`);
+  }
+  if (hit.hierarchy.lvl6 != null) {
+    val = val.concat(` > ${hit.hierarchy.lvl6}`);
+  }
+  return val;
+}
+
+export async function queryAlgolia(
+  message: string | Array<string>,
+): Promise<Array<string>> {
+  const {results} = await ALGOLIA_CLIENT.search<DocSearchHit>({
+    requests: [
+      {
+        query: Array.isArray(message) ? message.join('\n') : message,
+        indexName: ALGOLIA_CONFIG.indexName,
+        attributesToRetrieve: [
+          'hierarchy.lvl0',
+          'hierarchy.lvl1',
+          'hierarchy.lvl2',
+          'hierarchy.lvl3',
+          'hierarchy.lvl4',
+          'hierarchy.lvl5',
+          'hierarchy.lvl6',
+          'content',
+          'url',
+        ],
+        attributesToSnippet: [
+          `hierarchy.lvl1:10`,
+          `hierarchy.lvl2:10`,
+          `hierarchy.lvl3:10`,
+          `hierarchy.lvl4:10`,
+          `hierarchy.lvl5:10`,
+          `hierarchy.lvl6:10`,
+          `content:10`,
+        ],
+        snippetEllipsisText: '…',
+        hitsPerPage: 30,
+        attributesToHighlight: [
+          'hierarchy.lvl0',
+          'hierarchy.lvl1',
+          'hierarchy.lvl2',
+          'hierarchy.lvl3',
+          'hierarchy.lvl4',
+          'hierarchy.lvl5',
+          'hierarchy.lvl6',
+          'content',
+        ],
+      },
+    ],
+  });
+  const firstResult = results[0] as SearchResponse<DocSearchHit>;
+  const {hits} = firstResult;
+  const deduped = new Map();
+  for (const hit of hits) {
+    // drop hashes to dedupe properly
+    const u = new URL(hit.url);
+    if (deduped.has(u.pathname)) {
+      continue;
+    }
+    deduped.set(u.pathname, hit);
+  }
+  const pages: Array<string | null> = await Promise.all(
+    Array.from(deduped.values()).map(hit => {
+      return fetch(hit.url, {
+        headers: {
+          'User-Agent':
+            'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36',
+        },
+      }).then(res => {
+        if (res.ok === true) {
+          return res.text();
+        } else {
+          console.error(
+            `Could not fetch docs: ${res.status} ${res.statusText}`,
+          );
+          return null;
+        }
+      });
+    }),
+  );
+  return pages.filter(page => page !== null);
+}

compiler/packages/react-mcp-server/src/utils/assertExhaustive.ts

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * Trigger an exhaustiveness check in TypeScript and throw at runtime.
+ */
+export default function assertExhaustive(_: never, errorMsg: string): never {
+  throw new Error(errorMsg);
+}

compiler/packages/react-mcp-server/todo.md

@@ -0,0 +1,5 @@
+TODO
+
+- [ ] If code doesnt compile, read diagnostics and try again
+- [ ] Provide detailed examples in assistant prompt (use another LLM to generate good prompts, iterate from there)
+- [ ] Provide more tools for working with HIR/AST (eg so we can prompt it to try and optimize code via HIR, which it can then translate back into user code changes)