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compiler: Allow global mutation in jsx props

Browse Source 
Fixes https://x.com/raibima/status/1794395807216738792

The issue is that if you pass a global-modifying function as prop to JSX, we currently report that it's invalid to modify a global during rendering. The problem is that we don't really know when/if the child component will actually call that function prop. It would be against the rules to call the function during render, but it's totally fine to call it during an event handler or from a useEffect.

Since we don't know at the call-site how the child will use the function, we should allow such calls. In the future we could improve this in a few ways:
* For all functions that modify globals, codegen an assertion or warning into the function that fires if it's called "during render". We'd have to precisely define what "during render" is, but this would at least help developers catch this dynamically.
* Use the type system to distinguish "event/effect" and "render" functions to help developers avoid accidentally mutating globals during render.

ghstack-source-id: 4aba4e6d214fd6c062e4029294efe9b8fe25cd83
Pull Request resolved: https://github.com/facebook/react/pull/29591
This commit is contained in:
Joe Savona
2024-05-25 22:03:52 +01:00
parent e2e12f3351
commit 49ed6f0740
13 changed files with 331 additions and 47 deletions
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51
compiler/packages/babel-plugin-react-compiler/src/Inference/InferReferenceEffects.ts
View File

@@ -1103,13 +1103,56 @@ function inferBlock(
break;
}
case "JsxExpression": {
valueKind = {
if (instrValue.tag.kind === "Identifier") {
state.referenceAndRecordEffects(
instrValue.tag,
Effect.Freeze,
ValueReason.JsxCaptured,
functionEffects
);
}
if (instrValue.children !== null) {
for (const child of instrValue.children) {
state.referenceAndRecordEffects(
child,
Effect.Freeze,
ValueReason.JsxCaptured,
functionEffects
);
}
}
for (const attr of instrValue.props) {
if (attr.kind === "JsxSpreadAttribute") {
state.referenceAndRecordEffects(
attr.argument,
Effect.Freeze,
ValueReason.JsxCaptured,
functionEffects
);
} else {
const propEffects: Array<FunctionEffect> = [];
state.referenceAndRecordEffects(
attr.place,
Effect.Freeze,
ValueReason.JsxCaptured,
propEffects
);
functionEffects.push(
...propEffects.filter(
(propEffect) => propEffect.kind !== "GlobalMutation"
)
);
}
}
state.initialize(instrValue, {
kind: ValueKind.Frozen,
reason: new Set([ValueReason.Other]),
context: new Set(),
};
effect = { kind: Effect.Freeze, reason: ValueReason.JsxCaptured };
break;
});
state.define(instr.lvalue, instrValue);
instr.lvalue.effect = Effect.ConditionallyMutate;
continue;
}
case "JsxFragment": {
valueKind = {

86
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/allow-modify-global-in-callback-jsx.expect.md Normal file
View File

@@ -0,0 +1,86 @@
## Input
```javascript
import { useMemo } from "react";
const someGlobal = { value: 0 };
function Component({ value }) {
const onClick = () => {
someGlobal.value = value;
};
return useMemo(() => {
return <div onClick={onClick}>{someGlobal.value}</div>;
}, []);
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{ value: 0 }],
sequentialRenders: [
{ value: 1 },
{ value: 1 },
{ value: 42 },
{ value: 42 },
{ value: 0 },
],
};
```
## Code
```javascript
import { c as _c } from "react/compiler-runtime";
import { useMemo } from "react";
const someGlobal = { value: 0 };
function Component(t0) {
const $ = _c(4);
const { value } = t0;
let t1;
if ($[0] !== value) {
t1 = () => {
someGlobal.value = value;
};
$[0] = value;
$[1] = t1;
} else {
t1 = $[1];
}
const onClick = t1;
let t2;
let t3;
if ($[2] !== onClick) {
t3 = <div onClick={onClick}>{someGlobal.value}</div>;
$[2] = onClick;
$[3] = t3;
} else {
t3 = $[3];
}
t2 = t3;
return t2;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{ value: 0 }],
sequentialRenders: [
{ value: 1 },
{ value: 1 },
{ value: 42 },
{ value: 42 },
{ value: 0 },
],
};
```
### Eval output
(kind: ok) <div>0</div>
<div>0</div>
<div>0</div>
<div>0</div>
<div>0</div>

24
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/allow-modify-global-in-callback-jsx.js Normal file
View File

@@ -0,0 +1,24 @@
import { useMemo } from "react";
const someGlobal = { value: 0 };
function Component({ value }) {
const onClick = () => {
someGlobal.value = value;
};
return useMemo(() => {
return <div onClick={onClick}>{someGlobal.value}</div>;
}, []);
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{ value: 0 }],
sequentialRenders: [
{ value: 1 },
{ value: 1 },
{ value: 42 },
{ value: 42 },
{ value: 0 },
],
};

53
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/allow-reassignment-to-global-function-jsx-prop.expect.md Normal file
View File

@@ -0,0 +1,53 @@
## Input
```javascript
function Component() {
const onClick = () => {
// Cannot assign to globals
someUnknownGlobal = true;
moduleLocal = true;
};
// It's possible that this could be an event handler / effect function,
// but we don't know that and optimistically assume it will only be
// called by an event handler or effect, where it is allowed to modify globals
return <div onClick={onClick} />;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{}],
};
```
## Code
```javascript
import { c as _c } from "react/compiler-runtime";
function Component() {
const $ = _c(1);
let t0;
if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
const onClick = () => {
someUnknownGlobal = true;
moduleLocal = true;
};
t0 = <div onClick={onClick} />;
$[0] = t0;
} else {
t0 = $[0];
}
return t0;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{}],
};
```
### Eval output
(kind: ok) <div></div>

16
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/allow-reassignment-to-global-function-jsx-prop.js Normal file
View File

@@ -0,0 +1,16 @@
function Component() {
const onClick = () => {
// Cannot assign to globals
someUnknownGlobal = true;
moduleLocal = true;
};
// It's possible that this could be an event handler / effect function,
// but we don't know that and optimistically assume it will only be
// called by an event handler or effect, where it is allowed to modify globals
return <div onClick={onClick} />;
}
export const FIXTURE_ENTRYPOINT = {
fn: Component,
params: [{}],
};

27
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-component-tag-function.expect.md Normal file
View File

@@ -0,0 +1,27 @@
## Input
```javascript
function Component() {
const Foo = () => {
someGlobal = true;
};
return <Foo />;
}
```
## Error
```
1 | function Component() {
2 | const Foo = () => {
> 3 | someGlobal = true;
| ^^^^^^^^^^ InvalidReact: Unexpected reassignment of a variable which was defined outside of the component. Components and hooks should be pure and side-effect free, but variable reassignment is a form of side-effect. If this variable is used in rendering, use useState instead. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render) (3:3)
4 | };
5 | return <Foo />;
6 | }
```

6
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-component-tag-function.js Normal file
View File

@@ -0,0 +1,6 @@
function Component() {
const Foo = () => {
someGlobal = true;
};
return <Foo />;
}

30
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-children.expect.md Normal file
View File

@@ -0,0 +1,30 @@
## Input
```javascript
function Component() {
const foo = () => {
someGlobal = true;
};
// Children are generally access/called during render, so
// modifying a global in a children function is almost
// certainly a mistake.
return <Foo>{foo}</Foo>;
}
```
## Error
```
1 | function Component() {
2 | const foo = () => {
> 3 | someGlobal = true;
| ^^^^^^^^^^ InvalidReact: Unexpected reassignment of a variable which was defined outside of the component. Components and hooks should be pure and side-effect free, but variable reassignment is a form of side-effect. If this variable is used in rendering, use useState instead. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render) (3:3)
4 | };
5 | // Children are generally access/called during render, so
6 | // modifying a global in a children function is almost
```

9
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-children.js Normal file
View File

@@ -0,0 +1,9 @@
function Component() {
const foo = () => {
someGlobal = true;
};
// Children are generally access/called during render, so
// modifying a global in a children function is almost
// certainly a mistake.
return <Foo>{foo}</Foo>;
}

27
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-spread-attribute.expect.md Normal file
View File

@@ -0,0 +1,27 @@
## Input
```javascript
function Component() {
const foo = () => {
someGlobal = true;
};
return <div {...foo} />;
}
```
## Error
```
1 | function Component() {
2 | const foo = () => {
> 3 | someGlobal = true;
| ^^^^^^^^^^ InvalidReact: Unexpected reassignment of a variable which was defined outside of the component. Components and hooks should be pure and side-effect free, but variable reassignment is a form of side-effect. If this variable is used in rendering, use useState instead. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render) (3:3)
4 | };
5 | return <div {...foo} />;
6 | }
```

6
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-spread-attribute.js Normal file
View File

@@ -0,0 +1,6 @@
function Component() {
const foo = () => {
someGlobal = true;
};
return <div {...foo} />;
}

32
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.reassignment-to-global-function-prop.expect.md
View File

@@ -1,32 +0,0 @@
## Input
```javascript
function Component() {
const foo = () => {
// Cannot assign to globals
someUnknownGlobal = true;
moduleLocal = true;
};
// It's possible that this could be an event handler / effect function,
// but we don't know that and conservatively assume it's a render helper
// where it's disallowed to modify globals
return <Foo foo={foo} />;
}
```
## Error
```
2 | const foo = () => {
3 | // Cannot assign to globals
> 4 | someUnknownGlobal = true;
| ^^^^^^^^^^^^^^^^^ InvalidReact: Unexpected reassignment of a variable which was defined outside of the component. Components and hooks should be pure and side-effect free, but variable reassignment is a form of side-effect. If this variable is used in rendering, use useState instead. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render) (4:4)
5 | moduleLocal = true;
6 | };
7 | // It's possible that this could be an event handler / effect function,
```

11
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.reassignment-to-global-function-prop.js
View File

@@ -1,11 +0,0 @@
function Component() {
const foo = () => {
// Cannot assign to globals
someUnknownGlobal = true;
moduleLocal = true;
};
// It's possible that this could be an event handler / effect function,
// but we don't know that and conservatively assume it's a render helper
// where it's disallowed to modify globals
return <Foo foo={foo} />;
}