[compiler][rfc] Enable hook guards in dev mode by default

This validation ensures that React compiler-enabled apps remain correct. That is, code that errors with this validation is most likely ***invalid*** with React compiler is enabled (specifically, hook calls will be compiled to if-else memo blocks).

Hook guards are used extensively for Meta's react compiler rollouts. There, they're enabled for developers (for dev builds) and on e2e test runs. Let's enable by default for oss as well

### Examples of inputs this rule throws on

* Components should not be invoked directly as React Compiler could memoize the call to AnotherComponent, which introduces conditional hook calls in its compiled output.
  ```js
  function Invalid1(props) {
   const myJsx = AnotherComponent(props);
   return <div> { myJsx } </div>;
  }
  ```
* Hooks must be named as hooks. Similarly, hook calls may not appear in functions that are not components or hooks.
  ```js
  const renamedHook = useState;
  function Invalid2() {
    const [state, setState] = renamedHook(0);
  }

  function Invalid3() {
    const myFunc = () => useContext(...);
    myFunc();
  }
  ```

* Hooks must be directly called (from the body of a component or hook)
  ```
  function call(fn) {
    return fn();
  }

  function Invalid4() {
    const result = call(useMyHook);
  }
  ```

compiler/packages/babel-plugin-react-compiler/package.json

@@ -50,6 +50,7 @@
     "pretty-format": "^24",
     "react": "0.0.0-experimental-4beb1fd8-20241118",
     "react-dom": "0.0.0-experimental-4beb1fd8-20241118",
+    "react-compiler-runtime": "0.0.1",
     "ts-jest": "^29.1.1",
     "ts-node": "^10.9.2",
     "zod": "^3.22.4",

compiler/packages/babel-plugin-react-compiler/scripts/jest/makeTransform.ts

@@ -29,6 +29,7 @@ const e2eTransformerCacheKey = 1;
 const forgetOptions: EnvironmentConfig = validateEnvironmentConfig({
   enableAssumeHooksFollowRulesOfReact: true,
   enableFunctionOutlining: false,
+  enableEmitHookGuards: null,
 });
 const debugMode = process.env['DEBUG_FORGET_COMPILER'] != null;
 

compiler/packages/babel-plugin-react-compiler/src/Babel/BabelPlugin.ts

@@ -61,6 +61,18 @@ export default function BabelPluginReactCompiler(
               },
             };
           }
+          if (opts.environment.enableEmitHookGuards != null) {
+            const enableEmitHookGuards = opts.environment.enableEmitHookGuards;
+            if (enableEmitHookGuards.devonly === true && !isDev) {
+              opts = {
+                ...opts,
+                environment: {
+                  ...opts.environment,
+                  enableEmitHookGuards: null,
+                },
+              };
+            }
+          }
           compileProgram(prog, {
             opts,
             filename: pass.filename ?? null,

compiler/packages/babel-plugin-react-compiler/src/HIR/Environment.ts

@@ -396,7 +396,27 @@ const EnvironmentConfigSchema = z.object({
    */
   enableEmitFreeze: ExternalFunctionSchema.nullable().default(null),
 
-  enableEmitHookGuards: ExternalFunctionSchema.nullable().default(null),
+  enableEmitHookGuards: z
+    .intersection(
+      ExternalFunctionSchema,
+      z.object({
+        devonly: z.union([
+          z.literal(true),
+          z.literal(false),
+          /**
+           * Backwards compatibility with previous configuration, which did not
+           * have this field.
+           */
+          z.literal(undefined),
+        ]),
+      }),
+    )
+    .nullable()
+    .default({
+      source: 'react-compiler-runtime',
+      importSpecifierName: '$dispatcherGuard',
+      devonly: true,
+    }),
 
   /**
    * Enable instruction reordering. See InstructionReordering.ts for the details
@@ -668,6 +688,7 @@ const testComplexConfigDefaults: PartialEnvironmentConfig = {
   enableEmitHookGuards: {
     source: 'react-compiler-runtime',
     importSpecifierName: '$dispatcherGuard',
+    devonly: false,
   },
   inlineJsxTransform: {
     elementSymbol: 'react.transitional.element',
@@ -711,6 +732,7 @@ function parseConfigPragmaEnvironmentForTest(
   const maybeConfig: any = {};
   // Get the defaults to programmatically check for boolean properties
   const defaultConfig = EnvironmentConfigSchema.parse({});
+  (maybeConfig as PartialEnvironmentConfig).enableEmitHookGuards = null;
 
   for (const token of pragma.split(' ')) {
     if (!token.startsWith('@')) {

compiler/packages/react-compiler-runtime/src/index.ts

@@ -41,7 +41,6 @@ export const c =
 
 const LazyGuardDispatcher: {[key: string]: (...args: Array<any>) => any} = {};
 [
-  'readContext',
   'useCallback',
   'useContext',
   'useEffect',
@@ -58,10 +57,8 @@ const LazyGuardDispatcher: {[key: string]: (...args: Array<any>) => any} = {};
   'useMutableSource',
   'useSyncExternalStore',
   'useId',
-  'unstable_isNewReconciler',
-  'getCacheSignal',
-  'getCacheForType',
   'useCacheRefresh',
+  'useOptimistic',
 ].forEach(name => {
   LazyGuardDispatcher[name] = () => {
     throw new Error(
@@ -74,15 +71,29 @@ const LazyGuardDispatcher: {[key: string]: (...args: Array<any>) => any} = {};
 let originalDispatcher: unknown = null;
 
 // Allow guards are not emitted for useMemoCache
-LazyGuardDispatcher['useMemoCache'] = (count: number) => {
-  if (originalDispatcher == null) {
-    throw new Error(
-      'React Compiler internal invariant violation: unexpected null dispatcher',
-    );
-  } else {
-    return (originalDispatcher as any).useMemoCache(count);
-  }
-};
+
+for (const key of [
+  // Allow guards may not be emitted for useMemoCache
+  'useMemoCache',
+  'unstable_useMemoCache',
+  // Not named as hooks
+  'readContext',
+  'unstable_isNewReconciler',
+  'getCacheSignal',
+  'getCacheForType',
+  // Not 'real' hooks (i.e. not implemented with an index based id)
+  'use',
+]) {
+  LazyGuardDispatcher[key] = (...args) => {
+    if (originalDispatcher == null) {
+      throw new Error(
+        'React Compiler internal invariant violation: unexpected null dispatcher',
+      );
+    } else {
+      return (originalDispatcher as any).useMemoCache(...args);
+    }
+  };
+}
 
 enum GuardKind {
   PushGuardContext = 0,
@@ -92,8 +103,13 @@ enum GuardKind {
 }
 
 function setCurrent(newDispatcher: any) {
-  ReactSecretInternals.ReactCurrentDispatcher.current = newDispatcher;
-  return ReactSecretInternals.ReactCurrentDispatcher.current;
+  if (ReactSecretInternals.ReactCurrentDispatcher != null) {
+    ReactSecretInternals.ReactCurrentDispatcher.current = newDispatcher;
+    return ReactSecretInternals.ReactCurrentDispatcher.current;
+  } else {
+    ReactSecretInternals.H = newDispatcher;
+    return ReactSecretInternals.H;
+  }
 }
 
 const guardFrames: Array<unknown> = [];
@@ -134,7 +150,9 @@ const guardFrames: Array<unknown> = [];
  * ```
  */
 export function $dispatcherGuard(kind: GuardKind) {
-  const curr = ReactSecretInternals.ReactCurrentDispatcher.current;
+  const curr =
+    ReactSecretInternals.H ??
+    ReactSecretInternals.ReactCurrentDispatcher.current;
   if (kind === GuardKind.PushGuardContext) {
     // Push before checking invariant or errors
     guardFrames.push(curr);
@@ -169,7 +187,29 @@ export function $dispatcherGuard(kind: GuardKind) {
     // ExpectHooks could be nested, so we save the current dispatcher
     // for the matching PopExpectHook to restore.
     guardFrames.push(curr);
-    setCurrent(originalDispatcher);
+    if (originalDispatcher != null) {
+      /**
+       * originalDispatcher could be null in the following case.
+       * ```js
+       * function Component() {
+       *   "use no memo";
+       *   const useFn = useMakeHook();
+       *   useFn();
+       * }
+       * function useMakeHook() {
+       *   // ...
+       *   return () => {
+       *     useState(...);
+       *   };
+       * }
+       * ```
+       *
+       * React compiler currently does not memoize within inner functions. While this
+       * code breaks the programming model (hooks as first class values), let's
+       * either ignore this or error with a better message (within another dispatcher)
+       */
+      setCurrent(originalDispatcher);
+    }
   } else if (kind === GuardKind.PopExpectHook) {
     const lastFrame = guardFrames.pop();
     if (lastFrame == null) {