[compiler] Repro for false positive mutation of a value derived from props

Repro from the compiler WG (Thanks Cody!) of a case where the compiler incorrectly thinks a value is mutable.

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

@@ -22,7 +22,6 @@ import {
   BasicBlock,
   isUseRefType,
   SourceLocation,
-  ArrayExpression,
 } from '../HIR';
 import {eachInstructionLValue, eachInstructionOperand} from '../HIR/visitors';
 import {isMutable} from '../ReactiveScopes/InferReactiveScopeVariables';
@@ -37,17 +36,11 @@ type DerivationMetadata = {
   isStateSource: boolean;
 };
 
-type EffectMetadata = {
-  effect: HIRFunction;
-  dependencies: ArrayExpression;
-};
-
 type ValidationContext = {
   readonly functions: Map<IdentifierId, FunctionExpression>;
-  readonly candidateDependencies: Map<IdentifierId, ArrayExpression>;
   readonly errors: CompilerError;
   readonly derivationCache: DerivationCache;
-  readonly effectsCache: Map<IdentifierId, EffectMetadata>;
+  readonly effects: Set<HIRFunction>;
   readonly setStateLoads: Map<IdentifierId, IdentifierId | null>;
   readonly setStateUsages: Map<IdentifierId, Set<SourceLocation>>;
 };
@@ -182,20 +175,18 @@ export function validateNoDerivedComputationsInEffects_exp(
   fn: HIRFunction,
 ): Result<void, CompilerError> {
   const functions: Map<IdentifierId, FunctionExpression> = new Map();
-  const candidateDependencies: Map<IdentifierId, ArrayExpression> = new Map();
   const derivationCache = new DerivationCache();
   const errors = new CompilerError();
-  const effectsCache: Map<IdentifierId, EffectMetadata> = new Map();
+  const effects: Set<HIRFunction> = new Set();
 
   const setStateLoads: Map<IdentifierId, IdentifierId> = new Map();
   const setStateUsages: Map<IdentifierId, Set<SourceLocation>> = new Map();
 
   const context: ValidationContext = {
     functions,
-    candidateDependencies,
     errors,
     derivationCache,
-    effectsCache,
+    effects,
     setStateLoads,
     setStateUsages,
   };
@@ -238,8 +229,8 @@ export function validateNoDerivedComputationsInEffects_exp(
     isFirstPass = false;
   } while (context.derivationCache.snapshot());
 
-  for (const [, effect] of effectsCache) {
-    validateEffect(effect.effect, effect.dependencies, context);
+  for (const effect of effects) {
+    validateEffect(effect, context);
   }
 
   return errors.asResult();
@@ -363,14 +354,8 @@ function recordInstructionDerivations(
       value.args[1].kind === 'Identifier'
     ) {
       const effectFunction = context.functions.get(value.args[0].identifier.id);
-      const deps = context.candidateDependencies.get(
-        value.args[1].identifier.id,
-      );
-      if (effectFunction != null && deps != null) {
-        context.effectsCache.set(value.args[0].identifier.id, {
-          effect: effectFunction.loweredFunc.func,
-          dependencies: deps,
-        });
+      if (effectFunction != null) {
+        context.effects.add(effectFunction.loweredFunc.func);
       }
     } else if (isUseStateType(lvalue.identifier) && value.args.length > 0) {
       typeOfValue = 'fromState';
@@ -382,8 +367,6 @@ function recordInstructionDerivations(
       );
       return;
     }
-  } else if (value.kind === 'ArrayExpression') {
-    context.candidateDependencies.set(lvalue.identifier.id, value);
   }
 
   for (const operand of eachInstructionOperand(instr)) {
@@ -613,7 +596,6 @@ function getFnLocalDeps(
 
 function validateEffect(
   effectFunction: HIRFunction,
-  dependencies: ArrayExpression,
   context: ValidationContext,
 ): void {
   const seenBlocks: Set<BlockId> = new Set();
@@ -630,16 +612,6 @@ function validateEffect(
     Set<SourceLocation>
   > = new Map();
 
-  // Consider setStates in the effect's dependency array as being part of effectSetStateUsages
-  for (const dep of dependencies.elements) {
-    if (dep.kind === 'Identifier') {
-      const root = getRootSetState(dep.identifier.id, context.setStateLoads);
-      if (root !== null) {
-        effectSetStateUsages.set(root, new Set([dep.loc]));
-      }
-    }
-  }
-
   let cleanUpFunctionDeps: Set<IdentifierId> | undefined;
 
   const globals: Set<IdentifierId> = new Set();
@@ -690,18 +662,6 @@ function validateEffect(
         instr.value.args.length === 1 &&
         instr.value.args[0].kind === 'Identifier'
       ) {
-        const calleeMetadata = context.derivationCache.cache.get(
-          instr.value.callee.identifier.id,
-        );
-
-        /*
-         * If the setState comes from a source other than local state skip
-         * since the fix is not to calculate in render
-         */
-        if (calleeMetadata?.typeOfValue != 'fromState') {
-          continue;
-        }
-
         const argMetadata = context.derivationCache.cache.get(
           instr.value.args[0].identifier.id,
         );

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/effect-derived-computations/effect-used-in-dep-array-still-errors.expect.md

@@ -1,63 +0,0 @@
-
-## Input
-
-```javascript
-// @validateNoDerivedComputationsInEffects_exp @loggerTestOnly
-
-function Component({prop}) {
-  const [s, setS] = useState(0);
-  useEffect(() => {
-    setS(prop);
-  }, [prop, setS]);
-
-  return <div>{prop}</div>;
-}
-
-```
-
-## Code
-
-```javascript
-import { c as _c } from "react/compiler-runtime"; // @validateNoDerivedComputationsInEffects_exp @loggerTestOnly
-
-function Component(t0) {
-  const $ = _c(5);
-  const { prop } = t0;
-  const [, setS] = useState(0);
-  let t1;
-  let t2;
-  if ($[0] !== prop) {
-    t1 = () => {
-      setS(prop);
-    };
-    t2 = [prop, setS];
-    $[0] = prop;
-    $[1] = t1;
-    $[2] = t2;
-  } else {
-    t1 = $[1];
-    t2 = $[2];
-  }
-  useEffect(t1, t2);
-  let t3;
-  if ($[3] !== prop) {
-    t3 = <div>{prop}</div>;
-    $[3] = prop;
-    $[4] = t3;
-  } else {
-    t3 = $[4];
-  }
-  return t3;
-}
-
-```
-
-## Logs
-
-```
-{"kind":"CompileError","detail":{"options":{"description":"Using an effect triggers an additional render which can hurt performance and user experience, potentially briefly showing stale values to the user\n\nThis setState call is setting a derived value that depends on the following reactive sources:\n\nProps: [prop]\n\nData Flow Tree:\n└── prop (Prop)\n\nSee: https://react.dev/learn/you-might-not-need-an-effect#updating-state-based-on-props-or-state","category":"EffectDerivationsOfState","reason":"You might not need an effect. Derive values in render, not effects.","details":[{"kind":"error","loc":{"start":{"line":6,"column":4,"index":150},"end":{"line":6,"column":8,"index":154},"filename":"effect-used-in-dep-array-still-errors.ts","identifierName":"setS"},"message":"This should be computed during render, not in an effect"}]}},"fnLoc":null}
-{"kind":"CompileSuccess","fnLoc":{"start":{"line":3,"column":0,"index":64},"end":{"line":10,"column":1,"index":212},"filename":"effect-used-in-dep-array-still-errors.ts"},"fnName":"Component","memoSlots":5,"memoBlocks":2,"memoValues":3,"prunedMemoBlocks":0,"prunedMemoValues":0}
-```
-      
-### Eval output
-(kind: exception) Fixture not implemented

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/effect-derived-computations/effect-used-in-dep-array-still-errors.js

@@ -1,10 +0,0 @@
-// @validateNoDerivedComputationsInEffects_exp @loggerTestOnly
-
-function Component({prop}) {
-  const [s, setS] = useState(0);
-  useEffect(() => {
-    setS(prop);
-  }, [prop, setS]);
-
-  return <div>{prop}</div>;
-}

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/effect-derived-computations/from-props-setstate-in-effect-no-error.expect.md

@@ -1,65 +0,0 @@
-
-## Input
-
-```javascript
-// @validateNoDerivedComputationsInEffects_exp @enableTreatSetIdentifiersAsStateSetters @loggerTestOnly
-
-function Component({setParentState, prop}) {
-  useEffect(() => {
-    setParentState(prop);
-  }, [prop]);
-
-  return <div>{prop}</div>;
-}
-
-```
-
-## Code
-
-```javascript
-import { c as _c } from "react/compiler-runtime"; // @validateNoDerivedComputationsInEffects_exp @enableTreatSetIdentifiersAsStateSetters @loggerTestOnly
-
-function Component(t0) {
-  const $ = _c(7);
-  const { setParentState, prop } = t0;
-  let t1;
-  if ($[0] !== prop || $[1] !== setParentState) {
-    t1 = () => {
-      setParentState(prop);
-    };
-    $[0] = prop;
-    $[1] = setParentState;
-    $[2] = t1;
-  } else {
-    t1 = $[2];
-  }
-  let t2;
-  if ($[3] !== prop) {
-    t2 = [prop];
-    $[3] = prop;
-    $[4] = t2;
-  } else {
-    t2 = $[4];
-  }
-  useEffect(t1, t2);
-  let t3;
-  if ($[5] !== prop) {
-    t3 = <div>{prop}</div>;
-    $[5] = prop;
-    $[6] = t3;
-  } else {
-    t3 = $[6];
-  }
-  return t3;
-}
-
-```
-
-## Logs
-
-```
-{"kind":"CompileSuccess","fnLoc":{"start":{"line":3,"column":0,"index":105},"end":{"line":9,"column":1,"index":240},"filename":"from-props-setstate-in-effect-no-error.ts"},"fnName":"Component","memoSlots":7,"memoBlocks":3,"memoValues":3,"prunedMemoBlocks":0,"prunedMemoValues":0}
-```
-      
-### Eval output
-(kind: exception) Fixture not implemented

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/effect-derived-computations/from-props-setstate-in-effect-no-error.js

@@ -1,9 +0,0 @@
-// @validateNoDerivedComputationsInEffects_exp @enableTreatSetIdentifiersAsStateSetters @loggerTestOnly
-
-function Component({setParentState, prop}) {
-  useEffect(() => {
-    setParentState(prop);
-  }, [prop]);
-
-  return <div>{prop}</div>;
-}

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/effect-derived-computations/usestate-derived-from-prop-no-show-in-data-flow-tree.expect.md

@@ -64,6 +64,7 @@ function Component(t0) {
 ## Logs
 
 ```
+{"kind":"CompileError","detail":{"options":{"description":"Using an effect triggers an additional render which can hurt performance and user experience, potentially briefly showing stale values to the user\n\nThis setState call is setting a derived value that depends on the following reactive sources:\n\nState: [second]\n\nData Flow Tree:\n└── second (State)\n\nSee: https://react.dev/learn/you-might-not-need-an-effect#updating-state-based-on-props-or-state","category":"EffectDerivationsOfState","reason":"You might not need an effect. Derive values in render, not effects.","details":[{"kind":"error","loc":{"start":{"line":14,"column":4,"index":443},"end":{"line":14,"column":8,"index":447},"filename":"usestate-derived-from-prop-no-show-in-data-flow-tree.ts","identifierName":"setS"},"message":"This should be computed during render, not in an effect"}]}},"fnLoc":null}
 {"kind":"CompileSuccess","fnLoc":{"start":{"line":3,"column":0,"index":64},"end":{"line":18,"column":1,"index":500},"filename":"usestate-derived-from-prop-no-show-in-data-flow-tree.ts"},"fnName":"Component","memoSlots":5,"memoBlocks":2,"memoValues":3,"prunedMemoBlocks":0,"prunedMemoValues":0}
 ```
       

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/new-mutability/error.todo-repro-destructure-from-prop-with-default-value.expect.md

@@ -0,0 +1,43 @@
+
+## Input
+
+```javascript
+export function useFormatRelativeTime(opts = {}) {
+  const {timeZone, minimal} = opts;
+  const format = useCallback(function formatWithUnit() {}, [minimal]);
+  // We record `{timeZone}` as capturing timeZone into the object,
+  // then assume that dateTimeFormat() mutates that object,
+  // which in turn can mutate timeZone and the object it came from,
+  // which means that the value `minimal` is derived from can change.
+  //
+  // The bug is that we shouldn't be recording a Capture effect given
+  // that `opts` is known maybe-frozen. If we correctly recorded
+  // an ImmutableCapture, this wouldn't be mistaken as mutating
+  // opts/minimal
+  dateTimeFormat({timeZone});
+  return format;
+}
+
+```
+
+
+## Error
+
+```
+Found 1 error:
+
+Compilation Skipped: Existing memoization could not be preserved
+
+React Compiler has skipped optimizing this component because the existing manual memoization could not be preserved. This dependency may be mutated later, which could cause the value to change unexpectedly.
+
+error.todo-repro-destructure-from-prop-with-default-value.ts:3:60
+  1 | export function useFormatRelativeTime(opts = {}) {
+  2 |   const {timeZone, minimal} = opts;
+> 3 |   const format = useCallback(function formatWithUnit() {}, [minimal]);
+    |                                                             ^^^^^^^ This dependency may be modified later
+  4 |   // We record `{timeZone}` as capturing timeZone into the object,
+  5 |   // then assume that dateTimeFormat() mutates that object,
+  6 |   // which in turn can mutate timeZone and the object it came from,
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/new-mutability/error.todo-repro-destructure-from-prop-with-default-value.js

@@ -0,0 +1,15 @@
+export function useFormatRelativeTime(opts = {}) {
+  const {timeZone, minimal} = opts;
+  const format = useCallback(function formatWithUnit() {}, [minimal]);
+  // We record `{timeZone}` as capturing timeZone into the object,
+  // then assume that dateTimeFormat() mutates that object,
+  // which in turn can mutate timeZone and the object it came from,
+  // which means that the value `minimal` is derived from can change.
+  //
+  // The bug is that we shouldn't be recording a Capture effect given
+  // that `opts` is known maybe-frozen. If we correctly recorded
+  // an ImmutableCapture, this wouldn't be mistaken as mutating
+  // opts/minimal
+  dateTimeFormat({timeZone});
+  return format;
+}