[DevTools] Exclude Suspense boundaries in hidden Activity (#34756)

Author: eps1lon

packages/react-devtools-shared/src/__tests__/store-test.js

@@ -3142,4 +3142,105 @@ describe('Store', () => {
     await actAsync(() => render(null));
     expect(store).toMatchInlineSnapshot(``);
   });
+
+  // @reactVersion >= 19
+  it('should keep suspended boundaries in the Suspense tree but not hidden Activity', async () => {
+    const Activity = React.Activity || React.unstable_Activity;
+
+    const never = new Promise(() => {});
+    function Never() {
+      readValue(never);
+      return null;
+    }
+    function Component({children}) {
+      return <div>{children}</div>;
+    }
+
+    function App({hidden}) {
+      return (
+        <>
+          <Activity mode={hidden ? 'hidden' : 'visible'}>
+            <React.Suspense name="inside-activity">
+              <Component key="inside-activity">inside Activity</Component>
+            </React.Suspense>
+          </Activity>
+          <React.Suspense name="outer-suspense">
+            <React.Suspense name="inner-suspense">
+              <Component key="inside-suspense">inside Suspense</Component>
+            </React.Suspense>
+            {hidden ? <Never /> : null}
+          </React.Suspense>
+        </>
+      );
+    }
+
+    await actAsync(() => {
+      render(<App hidden={true} />);
+    });
+
+    expect(store).toMatchInlineSnapshot(`
+      [root]
+        ▾ <App>
+            <Activity>
+            <Suspense name="outer-suspense">
+      [suspense-root]  rects={[{x:1,y:2,width:15,height:1}]}
+        <Suspense name="outer-suspense" rects={null}>
+    `);
+
+    // mount as visible
+    await actAsync(() => {
+      render(null);
+    });
+    await actAsync(() => {
+      render(<App hidden={false} />);
+    });
+
+    expect(store).toMatchInlineSnapshot(`
+      [root]
+        ▾ <App>
+          ▾ <Activity>
+            ▾ <Suspense name="inside-activity">
+                <Component key="inside-activity">
+          ▾ <Suspense name="outer-suspense">
+            ▾ <Suspense name="inner-suspense">
+                <Component key="inside-suspense">
+      [suspense-root]  rects={[{x:1,y:2,width:15,height:1}, {x:1,y:2,width:15,height:1}]}
+        <Suspense name="inside-activity" rects={[{x:1,y:2,width:15,height:1}]}>
+        <Suspense name="outer-suspense" rects={[{x:1,y:2,width:15,height:1}]}>
+          <Suspense name="inner-suspense" rects={[{x:1,y:2,width:15,height:1}]}>
+    `);
+
+    await actAsync(() => {
+      render(<App hidden={true} />);
+    });
+
+    expect(store).toMatchInlineSnapshot(`
+      [root]
+        ▾ <App>
+            <Activity>
+            <Suspense name="outer-suspense">
+      [suspense-root]  rects={[{x:1,y:2,width:15,height:1}, {x:1,y:2,width:15,height:1}]}
+        <Suspense name="outer-suspense" rects={[{x:1,y:2,width:15,height:1}]}>
+          <Suspense name="inner-suspense" rects={[{x:1,y:2,width:15,height:1}]}>
+    `);
+
+    await actAsync(() => {
+      render(<App hidden={false} />);
+    });
+
+    expect(store).toMatchInlineSnapshot(`
+      [root]
+        ▾ <App>
+          ▾ <Activity>
+            ▾ <Suspense name="inside-activity">
+                <Component key="inside-activity">
+          ▾ <Suspense name="outer-suspense">
+            ▾ <Suspense name="inner-suspense">
+                <Component key="inside-suspense">
+      [suspense-root]  rects={[{x:1,y:2,width:15,height:1}, {x:1,y:2,width:15,height:1}]}
+        <Suspense name="inside-activity" rects={[{x:1,y:2,width:15,height:1}]}>
+        <Suspense name="outer-suspense" rects={[{x:1,y:2,width:15,height:1}]}>
+          <Suspense name="inner-suspense" rects={[{x:1,y:2,width:15,height:1}]}>
+    `);
+  });
 });

packages/react-devtools-shared/src/backend/fiber/renderer.js

@@ -3144,12 +3144,30 @@ export function attach(
     }
   }
 
+  /**
+   * Offscreen of suspended Suspense
+   */
+  function isSuspendedOffscreen(fiber: Fiber): boolean {
+    switch (fiber.tag) {
+      case LegacyHiddenComponent:
+      // fallthrough since all published implementations currently implement the same state as Offscreen.
+      case OffscreenComponent:
+        return (
+          fiber.memoizedState !== null &&
+          fiber.return !== null &&
+          fiber.return.tag === SuspenseComponent
+        );
+      default:
+        return false;
+    }
+  }
+
   function unmountRemainingChildren() {
     if (
       reconcilingParent !== null &&
       (reconcilingParent.kind === FIBER_INSTANCE ||
         reconcilingParent.kind === FILTERED_FIBER_INSTANCE) &&
-      isHiddenOffscreen(reconcilingParent.data) &&
+      isSuspendedOffscreen(reconcilingParent.data) &&
       !isInDisconnectedSubtree
     ) {
       // This is a hidden offscreen, we need to execute this in the context of a disconnected subtree.
@@ -4026,7 +4044,7 @@ export function attach(
         trackDebugInfoFromHostComponent(nearestInstance, fiber);
       }
 
-      if (isHiddenOffscreen(fiber)) {
+      if (isSuspendedOffscreen(fiber)) {
         // If an Offscreen component is hidden, mount its children as disconnected.
         const stashedDisconnected = isInDisconnectedSubtree;
         isInDisconnectedSubtree = true;
@@ -4037,6 +4055,9 @@ export function attach(
         } finally {
           isInDisconnectedSubtree = stashedDisconnected;
         }
+      } else if (isHiddenOffscreen(fiber)) {
+        // hidden Activity is noisy.
+        // Including it may show overlapping Suspense rects
       } else if (fiber.tag === SuspenseComponent && OffscreenComponent === -1) {
         // Legacy Suspense without the Offscreen wrapper. For the modern Suspense we just handle the
         // Offscreen wrapper itself specially.
@@ -4981,6 +5002,8 @@ export function attach(
 
       const prevWasHidden = isHiddenOffscreen(prevFiber);
       const nextIsHidden = isHiddenOffscreen(nextFiber);
+      const prevWasSuspended = isSuspendedOffscreen(prevFiber);
+      const nextIsSuspended = isSuspendedOffscreen(nextFiber);
 
       if (isLegacySuspense) {
         if (
@@ -5058,8 +5081,8 @@ export function attach(
           );
           updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
         }
-      } else if (nextIsHidden) {
-        if (!prevWasHidden) {
+      } else if (nextIsSuspended) {
+        if (!prevWasSuspended) {
           // We're hiding the children. Disconnect them from the front end but keep state.
           if (fiberInstance !== null && !isInDisconnectedSubtree) {
             disconnectChildrenRecursively(remainingReconcilingChildren);
@@ -5077,7 +5100,7 @@ export function attach(
         } finally {
           isInDisconnectedSubtree = stashedDisconnected;
         }
-      } else if (prevWasHidden && !nextIsHidden) {
+      } else if (prevWasSuspended && !nextIsSuspended) {
         // We're revealing the hidden children. We now need to update them to the latest state.
         // We do this while still in the disconnected state and then we reconnect the new ones.
         // This avoids reconnecting things that are about to be removed anyway.
@@ -5103,6 +5126,13 @@ export function attach(
           // Children may have reordered while they were hidden.
           updateFlags |= ShouldResetChildren | ShouldResetSuspenseChildren;
         }
+      } else if (nextIsHidden) {
+        if (prevWasHidden) {
+          // still hidden. Nothing to do.
+        } else {
+          // We're hiding the children. Remove them from the Frontend
+          unmountRemainingChildren();
+        }
       } else if (
         nextFiber.tag === SuspenseComponent &&
         OffscreenComponent !== -1 &&
@@ -5259,7 +5289,7 @@ export function attach(
         // We need to crawl the subtree for closest non-filtered Fibers
         // so that we can display them in a flat children set.
         if (fiberInstance !== null && fiberInstance.kind === FIBER_INSTANCE) {
-          if (!nextIsHidden && !isInDisconnectedSubtree) {
+          if (!nextIsSuspended && !isInDisconnectedSubtree) {
             recordResetChildren(fiberInstance);
           }
 
@@ -5335,7 +5365,7 @@ export function attach(
       if (
         (child.kind === FIBER_INSTANCE ||
           child.kind === FILTERED_FIBER_INSTANCE) &&
-        isHiddenOffscreen(child.data)
+        isSuspendedOffscreen(child.data)
       ) {
         // This instance's children are already disconnected.
       } else {