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[compiler] More flexible/helpful lazy ref initialization (#34449)
Two small QoL improvements inspired by feedback: * `if (ref.current === undefined) { ref.current = ... }` is now allowed. * `if (!ref.current) { ref.current = ... }` is still disallowed, but we emit an extra hint suggesting the `if (!ref.current == null)` pattern. I was on the fence about the latter. We got feedback asking to allow `if (!ref.current)` but if your ref stores a boolean value then this would allow reading the ref in render. The unary form is also less precise in general due to sketchy truthiness conversions. I figured a hint is a good compromise. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34449). * __->__ #34449 * #34424 DiffTrain build for [bd9e6e0](bd9e6e0)
1 parent 23223ad commit 6e1b4fd

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‎compiled/eslint-plugin-react-hooks/index.js‎

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@@ -49448,12 +49448,46 @@ function validateNoRefAccessInRenderImpl(fn, env) {
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case 'StartMemoize':
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case 'FinishMemoize':
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break;
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case 'LoadGlobal': {
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if (instr.value.binding.name === 'undefined') {
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env.set(instr.lvalue.identifier.id, { kind: 'Nullable' });
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}
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break;
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}
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case 'Primitive': {
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if (instr.value.value == null) {
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env.set(instr.lvalue.identifier.id, { kind: 'Nullable' });
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}
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break;
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}
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case 'UnaryExpression': {
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if (instr.value.operator === '!') {
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const value = env.get(instr.value.value.identifier.id);
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const refId = (value === null || value === void 0 ? void 0 : value.kind) === 'RefValue' && value.refId != null
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? value.refId
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: null;
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if (refId !== null) {
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env.set(instr.lvalue.identifier.id, { kind: 'Guard', refId });
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errors.pushDiagnostic(CompilerDiagnostic.create({
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category: ErrorCategory.Refs,
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reason: 'Cannot access refs during render',
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description: ERROR_DESCRIPTION,
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})
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.withDetails({
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kind: 'error',
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loc: instr.value.value.loc,
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message: `Cannot access ref value during render`,
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})
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.withDetails({
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kind: 'hint',
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message: 'To initialize a ref only once, check that the ref is null with the pattern `if (ref.current == null) { ref.current = ... }`',
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}));
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break;
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}
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}
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validateNoRefValueAccess(errors, env, instr.value.value);
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break;
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}
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case 'BinaryExpression': {
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const left = env.get(instr.value.left.identifier.id);
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const right = env.get(instr.value.right.identifier.id);

‎compiled/facebook-www/REVISION‎

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‎compiled/facebook-www/REVISION_TRANSFORMS‎

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‎compiled/facebook-www/React-dev.classic.js‎

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@@ -1418,7 +1418,7 @@ __DEV__ &&
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exports.useTransition = function () {
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return resolveDispatcher().useTransition();
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};
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exports.version = "19.2.0-www-classic-835b0090-20250910";
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exports.version = "19.2.0-www-classic-bd9e6e0b-20250910";
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"undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
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"function" ===
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typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

‎compiled/facebook-www/React-dev.modern.js‎

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@@ -1418,7 +1418,7 @@ __DEV__ &&
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exports.useTransition = function () {
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return resolveDispatcher().useTransition();
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};
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exports.version = "19.2.0-www-modern-835b0090-20250910";
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exports.version = "19.2.0-www-modern-bd9e6e0b-20250910";
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"undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
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"function" ===
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typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

‎compiled/facebook-www/React-prod.classic.js‎

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@@ -600,4 +600,4 @@ exports.useSyncExternalStore = function (
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exports.useTransition = function () {
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return ReactSharedInternals.H.useTransition();
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};
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exports.version = "19.2.0-www-classic-835b0090-20250910";
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exports.version = "19.2.0-www-classic-bd9e6e0b-20250910";

‎compiled/facebook-www/React-prod.modern.js‎

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@@ -600,4 +600,4 @@ exports.useSyncExternalStore = function (
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exports.useTransition = function () {
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return ReactSharedInternals.H.useTransition();
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};
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exports.version = "19.2.0-www-modern-835b0090-20250910";
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exports.version = "19.2.0-www-modern-bd9e6e0b-20250910";

‎compiled/facebook-www/React-profiling.classic.js‎

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@@ -604,7 +604,7 @@ exports.useSyncExternalStore = function (
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exports.useTransition = function () {
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return ReactSharedInternals.H.useTransition();
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};
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exports.version = "19.2.0-www-classic-835b0090-20250910";
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exports.version = "19.2.0-www-classic-bd9e6e0b-20250910";
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"undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
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"function" ===
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typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

‎compiled/facebook-www/React-profiling.modern.js‎

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@@ -604,7 +604,7 @@ exports.useSyncExternalStore = function (
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exports.useTransition = function () {
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return ReactSharedInternals.H.useTransition();
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};
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exports.version = "19.2.0-www-modern-835b0090-20250910";
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exports.version = "19.2.0-www-modern-bd9e6e0b-20250910";
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"undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
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"function" ===
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typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

‎compiled/facebook-www/ReactART-dev.classic.js‎

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@@ -19708,10 +19708,10 @@ __DEV__ &&
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(function () {
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var internals = {
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bundleType: 1,
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version: "19.2.0-www-classic-835b0090-20250910",
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version: "19.2.0-www-classic-bd9e6e0b-20250910",
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rendererPackageName: "react-art",
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currentDispatcherRef: ReactSharedInternals,
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reconcilerVersion: "19.2.0-www-classic-835b0090-20250910"
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reconcilerVersion: "19.2.0-www-classic-bd9e6e0b-20250910"
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};
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internals.overrideHookState = overrideHookState;
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internals.overrideHookStateDeletePath = overrideHookStateDeletePath;
@@ -19745,7 +19745,7 @@ __DEV__ &&
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exports.Shape = Shape;
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exports.Surface = Surface;
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exports.Text = Text;
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exports.version = "19.2.0-www-classic-835b0090-20250910";
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exports.version = "19.2.0-www-classic-bd9e6e0b-20250910";
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"undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
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"function" ===
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typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

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