28f77b42dd
note: This implements the idea discussed in https://github.com/reactwg/react/discussions/389#discussioncomment-14252280 Currently we create `Impure` effects for impure functions like `Date.now()` or `Math.random()`, and then throw if the effect is reachable during render. However, impurity is a property of the resulting value: if the value isn't accessed during render then it's okay: maybe you're console-logging the time while debugging (fine), or storing the impure value into a ref and only accessing it in an effect or event handler (totally ok). This PR updates to validate that impure values are not transitively consumed during render, building on the `Render` effect. The validation currently uses an algorithm very similar to that of InferReactivePlaces - building a set of known impure values, starting with `Impure` effects as the sources and then flowing outward via data flow and mutations. If a transitively impure value reaches a `Render` effect, it's an error. We record both the source of the impure value and where it gets rendered to make it easier to understand and fix errors: ``` Error: Cannot access impure value during render Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent). error.invalid-impure-functions-in-render-via-render-helper.ts:10:25 8 | const array = makeArray(now); 9 | const hasDate = identity(array); > 10 | return <Bar hasDate={hasDate} />; | ^^^^^^^ Cannot access impure value during render 11 | }; 12 | return <Foo renderItem={renderItem} />; 13 | } error.invalid-impure-functions-in-render-via-render-helper.ts:6:14 4 | 5 | function Component() { > 6 | const now = Date.now(); | ^^^^^^^^^^ `Date.now` is an impure function. 7 | const renderItem = () => { 8 | const array = makeArray(now); 9 | const hasDate = identity(array); ``` Impure values are allowed to flow into refs, meaning that we now allow `useRef(Date.now())` or `useRef(localFunctionThatReturnsMathDotRandom())` which would have errored previously. The next PR reuses this improved impurity tracking to validate ref access in render as well.
eslint-plugin-react-compiler
ESLint plugin surfacing problematic React code found by the React compiler.
Installation
You'll first need to install ESLint:
npm i eslint --save-dev
Next, install eslint-plugin-react-compiler:
npm install eslint-plugin-react-compiler --save-dev
Usage
Flat config
Edit your eslint 8+ config (for example eslint.config.mjs) with the recommended configuration:
+ import reactCompiler from "eslint-plugin-react-compiler"
import react from "eslint-plugin-react"
export default [
// Your existing config
{ ...pluginReact.configs.flat.recommended, settings: { react: { version: "detect" } } },
+ reactCompiler.configs.recommended
]
Legacy config (.eslintrc)
Add react-compiler to the plugins section of your configuration file. You can omit the eslint-plugin- prefix:
{
"plugins": [
"react-compiler"
]
}
Then configure the rules you want to use under the rules section.
{
"rules": {
"react-compiler/react-compiler": "error"
}
}
Rules
TODO: Run eslint-doc-generator to generate the rules list.