[compiler] ValidateExhaustiveDeps disallows unnecessary non-reactive deps #34472
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This was referenced Sep 11, 2025
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mofeiZ
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The `@enablePreserveExistingMemoizationGuarantees` mode can still fail to preserve manual memoization due to mismtached dependencies. Specifically, where the user's dependencies are more precise than the compiler infers bc the compiler is being conservative about what might be nullable. In this mode though we're intentionally using information from the manual memoization and can also rely on the deps as a signal for what's non-nullable. The idea of the PR is that we treat manual memo deps just like other inferred-as-non-nullable objects during PropagateScopeDeps. We're careful to not treat the full path as non-nullable, only up to the last property index. So `x.y.z` as a manual dep treats `x` and `x.y` as non-nullable, allowing us to preserve a conditional dependency on `x.y.z`. Optionals within manual dependencies are a bit trickier and aren't handled yet, but hopefully that's less common and something we can improve in a follow-up. Not handling them just means that developers may hit false positives on validating existing memoization if they use optional chains in manual dependencies.
…ation The compiler currently drops manual memoization and rewrites it using its own inference. If the existing manual memo dependencies has missing or extra dependencies, compilation can change behavior by running the computation more often (if deps were missing) or less often (if there were extra deps). We currently address this by relying on the developer to use the ESLint plugin and have `eslint-disable-next-line react-hooks/exhaustive-deps` suppressions in their code. If a suppression exists, we skip compilation. But not everyone is using the linter! Relying on the linter is also imprecise since it forces us to bail out on exhaustive-deps checks that only effect (ahem) effects — and while it isn't good to have incorrect deps on effects, it isn't a problem for compilation. So this PR is a rough sketch of validating manual memoization dependencies in the compiler. Long-term we could use this to also check effect deps and replace the ExhaustiveDeps lint rule, but for now I'm focused specifically on manual memoization use-cases. If this works, we can stop bailing out on ESLint suppressions, since the compiler will implement all the appropriate checks (we already check rules of hooks).
Records more information in DropManualMemoization so that we know the full span of the manual dependencies array (if present). This allows ValidateExhaustiveDeps to include a suggestion with the correct deps.
…deps Just to be consistent, we disallow unnecessary deps even if they're known to be non-reactive.
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Just to be consistent, we disallow unnecessary deps even if they're known to be non-reactive.
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