[compiler] Reuse DropManualMemoization for ValidateNoVoidUseMemo #34001
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This was referenced Jul 25, 2025
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compiler/packages/babel-plugin-react-compiler/src/Inference/DropManualMemoization.ts
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| > 7 | console.log('computing'); | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | ||
| > 8 | }, []); | ||
| | ^^^^^^^^^ React Compiler has skipped optimizing this component because React.useMemo doesn't return a value. useMemo should only be used for memoizing values, not running arbitrary side effects. |
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I think we could make this a validation that only runs in the linter by default. The code was already memoizing something with side effects, so the compiler shouldn't make it worse — we have ValidatePreserveManualMemo to ensure that we don't change the memoization.
Let's write the message to remove the "RC has skipped optimizing..." text and focus on why the pattern is problematic.
compiler/packages/babel-plugin-react-compiler/src/Inference/DropManualMemoization.ts
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…33989) Adds a new property to ReturnTerminals to disambiguate whether it was explicit, implicit (arrow function expressions), or void (where it was omitted). I will use this property in the next PR adding a new validation pass. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33989). * #34022 * #34002 * #34001 * #33990 * __->__ #33989
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Adds a new validation pass to validate against `useMemo`s that don't return anything. This usually indicates some kind of "useEffect"-like code that has side effects that need to be memoized to prevent overfiring, and is an anti-pattern. A follow up validation could also look at the return value of `useMemo`s to see if they are being used. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33990). * #34022 * #34002 * #34001 * __->__ #33990 * #33989
Much of the logic in the new validation pass is already implemented in DropManualMemoization, so let's combine them. I opted to keep the environment flag so we can more precisely control the rollout.
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…33989) Adds a new property to ReturnTerminals to disambiguate whether it was explicit, implicit (arrow function expressions), or void (where it was omitted). I will use this property in the next PR adding a new validation pass. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33989). * #34022 * #34002 * #34001 * #33990 * __->__ #33989 DiffTrain build for [5dd622e](5dd622e)
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…33989) Adds a new property to ReturnTerminals to disambiguate whether it was explicit, implicit (arrow function expressions), or void (where it was omitted). I will use this property in the next PR adding a new validation pass. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33989). * #34022 * #34002 * #34001 * #33990 * __->__ #33989 DiffTrain build for [5dd622e](5dd622e)
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Adds a new validation pass to validate against `useMemo`s that don't return anything. This usually indicates some kind of "useEffect"-like code that has side effects that need to be memoized to prevent overfiring, and is an anti-pattern. A follow up validation could also look at the return value of `useMemo`s to see if they are being used. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33990). * #34022 * #34002 * #34001 * __->__ #33990 * #33989 DiffTrain build for [c60eebf](c60eebf)
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Adds a new validation pass to validate against `useMemo`s that don't return anything. This usually indicates some kind of "useEffect"-like code that has side effects that need to be memoized to prevent overfiring, and is an anti-pattern. A follow up validation could also look at the return value of `useMemo`s to see if they are being used. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33990). * #34022 * #34002 * #34001 * __->__ #33990 * #33989 DiffTrain build for [c60eebf](c60eebf)
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Much of the logic in the new validation pass is already implemented in DropManualMemoization, so let's combine them. I opted to keep the environment flag so we can more precisely control the rollout.
Stack created with Sapling. Best reviewed with ReviewStack.