Warn if calling setState outside of render but before commit

packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js

@@ -853,6 +853,75 @@ describe('ReactDOMServerPartialHydration', () => {
     expect(span.className).toBe('hi');
   });
 
+  // @gate experimental
+  it('warns but works if setState is called before commit in a dehydrated component', async () => {
+    let suspend = false;
+    let resolve;
+    const promise = new Promise(resolvePromise => (resolve = resolvePromise));
+
+    let updateText;
+
+    function Child() {
+      const [state, setState] = React.useState('Hello');
+      updateText = setState;
+      Scheduler.unstable_yieldValue('Child');
+      if (suspend) {
+        throw promise;
+      } else {
+        return state;
+      }
+    }
+
+    function Sibling() {
+      Scheduler.unstable_yieldValue('Sibling');
+      return null;
+    }
+
+    function App() {
+      return (
+        <div>
+          <Suspense fallback="Loading...">
+            <Child />
+            <Sibling />
+          </Suspense>
+        </div>
+      );
+    }
+
+    suspend = false;
+    const finalHTML = ReactDOMServer.renderToString(<App />);
+    expect(Scheduler).toHaveYielded(['Child', 'Sibling']);
+
+    const container = document.createElement('div');
+    container.innerHTML = finalHTML;
+
+    const root = ReactDOM.createRoot(container, {hydrate: true});
+
+    await act(async () => {
+      suspend = true;
+      root.render(<App />);
+      expect(Scheduler).toFlushAndYieldThrough(['Child']);
+
+      // While we're part way through the hydration, we update the state.
+      // This will schedule an update on the children of the suspense boundary.
+      expect(() => updateText('Hi')).toErrorDev(
+        "Can't perform a React state update on a component that hasn't mounted yet.",
+      );
+
+      // This will throw it away and rerender.
+      expect(Scheduler).toFlushAndYield(['Child', 'Sibling']);
+
+      expect(container.textContent).toBe('Hello');
+
+      suspend = false;
+      resolve();
+      await promise;
+    });
+    expect(Scheduler).toHaveYielded(['Child', 'Sibling']);
+
+    expect(container.textContent).toBe('Hello');
+  });
+
   // @gate experimental
   it('blocks the update to hydrate first if context has changed', async () => {
     let suspend = false;

packages/react-reconciler/src/ReactFiberBeginWork.new.js

@@ -3112,7 +3112,9 @@ function beginWork(
                 // been unsuspended it has committed as a resolved Suspense component.
                 // If it needs to be retried, it should have work scheduled on it.
                 workInProgress.effectTag |= DidCapture;
-                break;
+                // We should never render the children of a dehydrated boundary until we
+                // upgrade it. We return null instead of bailoutOnAlreadyFinishedWork.
+                return null;
               }
             }
 

packages/react-reconciler/src/ReactFiberBeginWork.old.js

@@ -1110,6 +1110,8 @@ function updateHostComponent(current, workInProgress, renderExpirationTime) {
     }
     // Schedule this fiber to re-render at offscreen priority. Then bailout.
     workInProgress.expirationTime = workInProgress.childExpirationTime = Never;
+    // We should never render the children of a dehydrated boundary until we
+    // upgrade it. We return null instead of bailoutOnAlreadyFinishedWork.
     return null;
   }
 
@@ -3128,7 +3130,8 @@ function beginWork(
                 // been unsuspended it has committed as a resolved Suspense component.
                 // If it needs to be retried, it should have work scheduled on it.
                 workInProgress.effectTag |= DidCapture;
-                break;
+
+                return null;
               }
             }
 

packages/react-reconciler/src/ReactFiberWorkLoop.new.js

@@ -76,6 +76,7 @@ import {
 } from './ReactTypeOfMode';
 import {
   HostRoot,
+  IndeterminateComponent,
   ClassComponent,
   SuspenseComponent,
   SuspenseListComponent,
@@ -500,6 +501,14 @@ function markUpdateLaneFromFiberToRoot(
   if (alternate !== null) {
     alternate.lanes = mergeLanes(alternate.lanes, lane);
   }
+  if (__DEV__) {
+    if (
+      alternate === null &&
+      (fiber.effectTag & (Placement | Hydrating)) !== NoEffect
+    ) {
+      warnAboutUpdateOnNotYetMountedFiberInDEV(fiber);
+    }
+  }
   // Walk the parent path to the root and update the child expiration time.
   let node = fiber.return;
   let root = null;
@@ -508,6 +517,14 @@ function markUpdateLaneFromFiberToRoot(
   } else {
     while (node !== null) {
       alternate = node.alternate;
+      if (__DEV__) {
+        if (
+          alternate === null &&
+          (node.effectTag & (Placement | Hydrating)) !== NoEffect
+        ) {
+          warnAboutUpdateOnNotYetMountedFiberInDEV(fiber);
+        }
+      }
       node.childLanes = mergeLanes(node.childLanes, lane);
       if (alternate !== null) {
         alternate.childLanes = mergeLanes(alternate.childLanes, lane);
@@ -2710,6 +2727,60 @@ function flushRenderPhaseStrictModeWarningsInDEV() {
   }
 }
 
+let didWarnStateUpdateForNotYetMountedComponent: Set<string> | null = null;
+function warnAboutUpdateOnNotYetMountedFiberInDEV(fiber) {
+  if (__DEV__) {
+    if ((executionContext & RenderContext) !== NoContext) {
+      // We let the other warning about render phase updates deal with this one.
+      return;
+    }
+
+    const tag = fiber.tag;
+    if (
+      tag !== IndeterminateComponent &&
+      tag !== HostRoot &&
+      tag !== ClassComponent &&
+      tag !== FunctionComponent &&
+      tag !== ForwardRef &&
+      tag !== MemoComponent &&
+      tag !== SimpleMemoComponent &&
+      tag !== Block
+    ) {
+      // Only warn for user-defined components, not internal ones like Suspense.
+      return;
+    }
+
+    // We show the whole stack but dedupe on the top component's name because
+    // the problematic code almost always lies inside that component.
+    const componentName = getComponentName(fiber.type) || 'ReactComponent';
+    if (didWarnStateUpdateForNotYetMountedComponent !== null) {
+      if (didWarnStateUpdateForNotYetMountedComponent.has(componentName)) {
+        return;
+      }
+      didWarnStateUpdateForNotYetMountedComponent.add(componentName);
+    } else {
+      didWarnStateUpdateForNotYetMountedComponent = new Set([componentName]);
+    }
+
+    const previousFiber = ReactCurrentFiberCurrent;
+    try {
+      setCurrentDebugFiberInDEV(fiber);
+      console.error(
+        "Can't perform a React state update on a component that hasn't mounted yet. " +
+          'This indicates that you have a side-effect in your render function that ' +
+          'asynchronously later calls tries to update the component. Move this work to ' +
+          'useEffect instead.',
+      );
+    } finally {
+      if (previousFiber) {
+        setCurrentDebugFiberInDEV(fiber);
+      } else {
+        resetCurrentDebugFiberInDEV();
+      }
+    }
+  }
+}
+
 let didWarnStateUpdateForUnmountedComponent: Set<string> | null = null;
 function warnAboutUpdateOnUnmountedFiberInDEV(fiber) {
   if (__DEV__) {

packages/react-reconciler/src/ReactFiberWorkLoop.old.js

@@ -96,6 +96,7 @@ import {
 } from './ReactTypeOfMode';
 import {
   HostRoot,
+  IndeterminateComponent,
   ClassComponent,
   SuspenseComponent,
   SuspenseListComponent,
@@ -498,6 +499,15 @@ function markUpdateTimeFromFiberToRoot(fiber, expirationTime) {
   if (alternate !== null && alternate.expirationTime < expirationTime) {
     alternate.expirationTime = expirationTime;
   }
+  if (__DEV__) {
+    if (
+      alternate === null &&
+      (fiber.effectTag & (Placement | Hydrating)) !== NoEffect
+    ) {
+      warnAboutUpdateOnNotYetMountedFiberInDEV(fiber);
+    }
+  }
+
   // Walk the parent path to the root and update the child expiration time.
   let node = fiber.return;
   let root = null;
@@ -506,6 +516,14 @@ function markUpdateTimeFromFiberToRoot(fiber, expirationTime) {
   } else {
     while (node !== null) {
       alternate = node.alternate;
+      if (__DEV__) {
+        if (
+          alternate === null &&
+          (node.effectTag & (Placement | Hydrating)) !== NoEffect
+        ) {
+          warnAboutUpdateOnNotYetMountedFiberInDEV(fiber);
+        }
+      }
       if (node.childExpirationTime < expirationTime) {
         node.childExpirationTime = expirationTime;
         if (
@@ -2901,6 +2919,60 @@ function flushRenderPhaseStrictModeWarningsInDEV() {
   }
 }
 
+let didWarnStateUpdateForNotYetMountedComponent: Set<string> | null = null;
+function warnAboutUpdateOnNotYetMountedFiberInDEV(fiber) {
+  if (__DEV__) {
+    if ((executionContext & RenderContext) !== NoContext) {
+      // We let the other warning about render phase updates deal with this one.
+      return;
+    }
+
+    const tag = fiber.tag;
+    if (
+      tag !== IndeterminateComponent &&
+      tag !== HostRoot &&
+      tag !== ClassComponent &&
+      tag !== FunctionComponent &&
+      tag !== ForwardRef &&
+      tag !== MemoComponent &&
+      tag !== SimpleMemoComponent &&
+      tag !== Block
+    ) {
+      // Only warn for user-defined components, not internal ones like Suspense.
+      return;
+    }
+
+    // We show the whole stack but dedupe on the top component's name because
+    // the problematic code almost always lies inside that component.
+    const componentName = getComponentName(fiber.type) || 'ReactComponent';
+    if (didWarnStateUpdateForNotYetMountedComponent !== null) {
+      if (didWarnStateUpdateForNotYetMountedComponent.has(componentName)) {
+        return;
+      }
+      didWarnStateUpdateForNotYetMountedComponent.add(componentName);
+    } else {
+      didWarnStateUpdateForNotYetMountedComponent = new Set([componentName]);
+    }
+
+    const previousFiber = ReactCurrentFiberCurrent;
+    try {
+      setCurrentDebugFiberInDEV(fiber);
+      console.error(
+        "Can't perform a React state update on a component that hasn't mounted yet. " +
+          'This indicates that you have a side-effect in your render function that ' +
+          'asynchronously later calls tries to update the component. Move this work to ' +
+          'useEffect instead.',
+      );
+    } finally {
+      if (previousFiber) {
+        setCurrentDebugFiberInDEV(fiber);
+      } else {
+        resetCurrentDebugFiberInDEV();
+      }
+    }
+  }
+}
+
 let didWarnStateUpdateForUnmountedComponent: Set<string> | null = null;
 function warnAboutUpdateOnUnmountedFiberInDEV(fiber) {
   if (__DEV__) {