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laurenandGitHub
cc2074aff8
## What
Codegen registers `_c` (the memo cache import) as a side effect whenever
a function compiles with memo slots. The registration persists on
`ProgramContext.imports` even if the function is later discarded (`'use
no forget'`, `'use no memo'`, lint mode, validation errors). If other
applied functions in the file compile to 0 memo slots, the stale `import
{ c as _c } from "react/compiler-runtime";` leaks into the output.
## Fix
In `applyCompiledFunctions`, drop the memo cache import if no applied
function uses memo slots. If `react/compiler-runtime` has no remaining
specifiers, drop the module entry too so we don't emit a bare `import
"react/compiler-runtime";`.
## Reproducer
`use-no-forget-multiple-with-eslint-suppression.js`:
```js
import {useRef} from 'react';
const useControllableState = options => {};
function NoopComponent() {}
function Component() {
'use no forget';
const ref = useRef(null);
// eslint-disable-next-line react-hooks/rules-of-hooks
ref.current = 'bad';
return <button ref={ref} />;
}
```
`NoopComponent` applies with 0 memo slots. `Component` is opted out, but
codegen already registered `_c` for it. Before:
```js
import { c as _c } from "react/compiler-runtime";
import { useRef } from "react";
```
After:
```js
import { useRef } from "react";
```
## Prior art
TS counterpart to the Rust port's fix in
7e26eb89fc3264a34a9f03a68ac7a870d9f74b51. That commit also added
`no-cache-slots-no-import.js`, which codifies the "no memo slots, no
import" rule.
## Test plan
- `yarn snap`: 1719/1719 passing
- Snapshot for `use-no-forget-multiple-with-eslint-suppression` loses
its spurious `_c` import
- `no-cache-slots-no-import` still passes
React Compiler
React Compiler is a compiler that optimizes React applications, ensuring that only the minimal parts of components and hooks will re-render when state changes. The compiler also validates that components and hooks follow the Rules of React.
More information about the design and architecture of the compiler are covered in the Design Goals.
More information about developing the compiler itself is covered in the Development Guide.