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[compiler] Allow extraneous non-reactive locals (#35190)
The existing exhaustive-deps rule allows omitting non-reactive dependencies, even if they're not memoized. Conceptually, if a value is non-reactive then it cannot semantically change. Even if the value is a new object, that object represents the exact same value and doesn't necessitate redoing downstream computation. Thus its fine to exclude nonreactive dependencies, whether they're a stable type or not. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/35190). * #35201 * #35202 * #35192 * __->__ #35190
Joseph Savona committed
Nov 24, 2025 at 12:18 UTC
67c1487ffd872c95a3bb7d8104eac6eca79fe8cb
3 files changed
+101
-58
compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateExhaustiveDependencies.ts
+38
-48
@@ -43,20 +43,37 @@ import {retainWhere} from '../Utils/utils';
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const DEBUG = false;
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/**
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- * Validates that existing manual memoization had exhaustive dependencies.
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- * Memoization with missing or extra reactive dependencies is invalid React
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- * and compilation can change behavior, causing a value to be computed more
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- * or less times.
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+ * Validates that existing manual memoization is exhaustive and does not
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+ * have extraneous dependencies. The goal of the validation is to ensure
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+ * that auto-memoization will not substantially change the behavior of
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+ * the program:
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+ * - If the manual dependencies were non-exhaustive (missing important deps)
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+ * then auto-memoization will include those dependencies, and cause the
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+ * value to update *more* frequently.
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+ * - If the manual dependencies had extraneous deps, then auto memoization
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+ * will remove them and cause the value to update *less* frequently.
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*
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- * TODOs:
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- * - Handle cases of mixed optional and non-optional versions of the same path,
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- * eg referecing both x.y.z and x.y?.z in the same memo block. we should collapse
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- * this into a single canonical dep that we look for in the manual deps. see the
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- * existing exhaustive deps rule for implementation.
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- * - Handle cases where the user deps were not simple identifiers + property chains.
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- * We try to detect this in ValidateUseMemo but we miss some cases. The problem
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- * is that invalid forms can be value blocks or function calls that don't get
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- * removed by DCE, leaving a structure like:
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+ * We consider a value V as missing if ALL of the following conditions are met:
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+ * - V is reactive
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+ * - There is no manual dependency path P such that whenever V would change,
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+ * P would also change. If V is `x.y.z`, this means there must be some
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+ * path P that is either `x.y.z`, `x.y`, or `x`. Note that we assume no
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+ * interior mutability, such that a shorter path "covers" changes to longer
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+ * more precise paths.
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+ *
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+ * We consider a value V extraneous if either of the folowing are true:
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+ * - V is a reactive local that is unreferenced
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+ * - V is a global that is unreferenced
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+ *
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+ * In other words, we allow extraneous non-reactive values since we know they cannot
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+ * impact how often the memoization would run.
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+ *
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+ * ## TODO: Invalid, Complex Deps
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+ *
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+ * Handle cases where the user deps were not simple identifiers + property chains.
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+ * We try to detect this in ValidateUseMemo but we miss some cases. The problem
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+ * is that invalid forms can be value blocks or function calls that don't get
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+ * removed by DCE, leaving a structure like:
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*
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* StartMemoize
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* t0 = <value to memoize>
@@ -209,31 +226,9 @@ export function validateExhaustiveDependencies(
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reason: 'Unexpected function dependency',
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loc: value.loc,
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});
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- /**
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- * Dependencies technically only need to include reactive values. However,
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- * reactivity inference for general values is subtle since it involves all
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- * of our complex control and data flow analysis. To keep results more
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- * stable and predictable to developers, we intentionally stay closer to
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- * the rules of the classic exhaustive-deps rule. Values should be included
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- * as dependencies if either of the following is true:
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- * - They're reactive
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- * - They're non-reactive and not a known-stable value type.
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- *
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- * Thus `const ref: Ref = cond ? ref1 : ref2` has to be a dependency
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- * (assuming `cond` is reactive) since it's reactive despite being a ref.
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- *
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- * Similarly, `const x = [1,2,3]` has to be a dependency since even
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- * though it's non reactive, it's not a known stable type.
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- *
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- * TODO: consider reimplementing a simpler form of reactivity inference.
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- * Ideally we'd consider `const ref: Ref = cond ? ref1 : ref2` as a required
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- * dependency even if our data/control flow tells us that `cond` is non-reactive.
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- * It's simpler for developers to reason about based on a more structural/AST
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- * driven approach.
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- */
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- const isRequiredDependency =
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- reactive.has(inferredDependency.identifier.id) ||
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- !isStableType(inferredDependency.identifier);
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+ const isRequiredDependency = reactive.has(
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+ inferredDependency.identifier.id,
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+ );
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let hasMatchingManualDependency = false;
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for (const manualDependency of manualDependencies) {
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if (
@@ -265,18 +260,13 @@ export function validateExhaustiveDependencies(
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extra.push(dep);
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}
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- /*
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- * For compatiblity with the existing exhaustive-deps rule, we allow
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- * known-stable values as dependencies even if the value is not reactive.
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- * This allows code that takes a dep on a non-reactive setState function
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- * to pass, for example.
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+ /**
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+ * Per docblock, we only consider dependencies as extraneous if
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+ * they are unused globals or reactive locals. Notably, this allows
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+ * non-reactive locals.
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*/
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retainWhere(extra, dep => {
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- const isNonReactiveStableValue =
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- dep.root.kind === 'NamedLocal' &&
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- !dep.root.value.reactive &&
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- isStableType(dep.root.value.identifier);
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- return !isNonReactiveStableValue;
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+ return dep.root.kind === 'Global' || dep.root.value.reactive;
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});
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if (missing.length !== 0 || extra.length !== 0) {
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/exhaustive-deps.expect.md
+50
-8
@@ -3,7 +3,7 @@
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```javascript
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// @validateExhaustiveMemoizationDependencies
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-import {useMemo} from 'react';
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+import {useCallback, useMemo} from 'react';
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import {makeObject_Primitives, Stringify} from 'shared-runtime';
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function useHook1(x) {
@@ -47,6 +47,16 @@ function useHook6(x) {
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}, [x]);
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}
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+function useHook7(x) {
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+ const [state, setState] = useState(true);
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+ const f = () => {
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+ setState(x => !x);
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+ };
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+ return useCallback(() => {
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+ f();
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+ }, [f]);
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+}
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+
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function Component({x, y, z}) {
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const a = useHook1(x);
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const b = useHook2(x);
@@ -54,7 +64,8 @@ function Component({x, y, z}) {
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const d = useHook4(x, y, z);
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const e = useHook5(x);
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const f = useHook6(x);
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- return <Stringify results={[a, b, c, d, e, f]} />;
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+ const g = useHook7(x);
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+ return <Stringify results={[a, b, c, d, e, f, g]} />;
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}
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```
@@ -63,7 +74,7 @@ function Component({x, y, z}) {
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```javascript
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import { c as _c } from "react/compiler-runtime"; // @validateExhaustiveMemoizationDependencies
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-import { useMemo } from "react";
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+import { useCallback, useMemo } from "react";
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import { makeObject_Primitives, Stringify } from "shared-runtime";
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function useHook1(x) {
@@ -121,8 +132,36 @@ function useHook6(x) {
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return f;
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}
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+function useHook7(x) {
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+ const $ = _c(2);
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+ const [, setState] = useState(true);
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+ let t0;
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+ if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
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+ t0 = () => {
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+ setState(_temp);
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+ };
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+ $[0] = t0;
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+ } else {
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+ t0 = $[0];
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+ }
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+ const f = t0;
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+ let t1;
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+ if ($[1] === Symbol.for("react.memo_cache_sentinel")) {
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+ t1 = () => {
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+ f();
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+ };
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+ $[1] = t1;
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+ } else {
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+ t1 = $[1];
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+ }
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+ return t1;
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+}
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+function _temp(x_0) {
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+ return !x_0;
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+}
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+
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function Component(t0) {
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- const $ = _c(7);
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+ const $ = _c(8);
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const { x, y, z } = t0;
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const a = useHook1(x);
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const b = useHook2(x);
@@ -130,6 +169,7 @@ function Component(t0) {
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const d = useHook4(x, y, z);
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const e = useHook5(x);
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const f = useHook6(x);
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+ const g = useHook7(x);
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let t1;
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if (
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$[0] !== a ||
@@ -137,18 +177,20 @@ function Component(t0) {
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$[2] !== c ||
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$[3] !== d ||
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$[4] !== e ||
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- $[5] !== f
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+ $[5] !== f ||
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+ $[6] !== g
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) {
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- t1 = <Stringify results={[a, b, c, d, e, f]} />;
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+ t1 = <Stringify results={[a, b, c, d, e, f, g]} />;
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$[0] = a;
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$[1] = b;
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$[2] = c;
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$[3] = d;
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$[4] = e;
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$[5] = f;
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- $[6] = t1;
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+ $[6] = g;
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+ $[7] = t1;
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} else {
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- t1 = $[6];
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+ t1 = $[7];
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}
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return t1;
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}
compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/exhaustive-deps.js
+13
-2
@@ -1,5 +1,5 @@
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// @validateExhaustiveMemoizationDependencies
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-import {useMemo} from 'react';
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+import {useCallback, useMemo} from 'react';
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import {makeObject_Primitives, Stringify} from 'shared-runtime';
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function useHook1(x) {
@@ -43,6 +43,16 @@ function useHook6(x) {
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}, [x]);
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}
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+function useHook7(x) {
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+ const [state, setState] = useState(true);
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+ const f = () => {
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+ setState(x => !x);
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+ };
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+ return useCallback(() => {
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+ f();
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+ }, [f]);
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+}
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+
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function Component({x, y, z}) {
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const a = useHook1(x);
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const b = useHook2(x);
@@ -50,5 +60,6 @@ function Component({x, y, z}) {
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const d = useHook4(x, y, z);
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const e = useHook5(x);
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const f = useHook6(x);
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- return <Stringify results={[a, b, c, d, e, f]} />;
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+ const g = useHook7(x);
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+ return <Stringify results={[a, b, c, d, e, f, g]} />;
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}