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[DevTools] Measure when reconnecting Suspense #35098

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Merged
eps1lon merged 2 commits into from
Nov 10, 2025
Merged

[DevTools] Measure when reconnecting Suspense #35098

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Current behavior
eps1lon Nov 10, 2025
273e94d
[DevTools] Measure when reconnecting Suspense
eps1lon Nov 10, 2025
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96 changes: 96 additions & 0 deletions packages/react-devtools-shared/src/__tests__/store-test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3298,4 +3298,100 @@ describe('Store', () => {
<Suspense name="Inner" rects={[{x:1,y:2,width:6,height:1}]}>
`);
});

// @reactVersion >= 19.0
it('measures rects when reconnecting', async () => {
function Component({children, promise}) {
let content = '';
if (promise) {
const value = readValue(promise);
if (typeof value === 'string') {
content += value;
}
}
return (
<div>
{content}
{children}
</div>
);
}

function App({outer, inner}) {
return (
<React.Suspense
name="outer"
fallback={<Component key="outer-fallback">loading outer</Component>}>
<Component key="outer-content" promise={outer}>
outer content
</Component>
<React.Suspense
name="inner"
fallback={
<Component key="inner-fallback">loading inner</Component>
}>
<Component key="inner-content" promise={inner}>
inner content
</Component>
</React.Suspense>
</React.Suspense>
);
}

await actAsync(() => {
render(<App outer={null} inner={null} />);
});

expect(store).toMatchInlineSnapshot(`
[root]
▾ <App>
▾ <Suspense name="outer">
<Component key="outer-content">
▾ <Suspense name="inner">
<Component key="inner-content">
[suspense-root] rects={[{x:1,y:2,width:13,height:1}, {x:1,y:2,width:13,height:1}]}
<Suspense name="outer" rects={[{x:1,y:2,width:13,height:1}, {x:1,y:2,width:13,height:1}]}>
<Suspense name="inner" rects={[{x:1,y:2,width:13,height:1}]}>
`);

let outerResolve;
const outerPromise = new Promise(resolve => {
outerResolve = resolve;
});

let innerResolve;
const innerPromise = new Promise(resolve => {
innerResolve = resolve;
});
await actAsync(() => {
render(<App outer={outerPromise} inner={innerPromise} />);
});

expect(store).toMatchInlineSnapshot(`
[root]
▾ <App>
▾ <Suspense name="outer">
<Component key="outer-fallback">
[suspense-root] rects={[{x:1,y:2,width:13,height:1}, {x:1,y:2,width:13,height:1}, {x:1,y:2,width:13,height:1}]}
<Suspense name="outer" rects={[{x:1,y:2,width:13,height:1}, {x:1,y:2,width:13,height:1}]}>
<Suspense name="inner" rects={[{x:1,y:2,width:13,height:1}]}>
`);

await actAsync(() => {
outerResolve('..');
innerResolve('.');
});

expect(store).toMatchInlineSnapshot(`
[root]
▾ <App>
▾ <Suspense name="outer">
<Component key="outer-content">
▾ <Suspense name="inner">
<Component key="inner-content">
[suspense-root] rects={[{x:1,y:2,width:15,height:1}, {x:1,y:2,width:14,height:1}]}
<Suspense name="outer" rects={[{x:1,y:2,width:15,height:1}, {x:1,y:2,width:14,height:1}]}>
<Suspense name="inner" rects={[{x:1,y:2,width:14,height:1}]}>
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@eps1lon eps1lon Nov 10, 2025 •
edited
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This measured a width of 13 without this change (see first commit) i.e. it was measuring without the resolved content.

`);
});
});
11 changes: 11 additions & 0 deletions packages/react-devtools-shared/src/backend/fiber/renderer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2586,6 +2586,17 @@ export function attach(
}
}
} else {
const suspenseNode = fiberInstance.suspenseNode;
if (suspenseNode !== null && fiber.memoizedState === null) {
// We're reconnecting an unsuspended Suspense. Measure to see if anything changed.
const prevRects = suspenseNode.rects;
const nextRects = measureInstance(fiberInstance);
if (!areEqualRects(prevRects, nextRects)) {
suspenseNode.rects = nextRects;
recordSuspenseResize(suspenseNode);
}
}

const {key} = fiber;
const displayName = getDisplayNameForFiber(fiber);
const elementType = getElementTypeForFiber(fiber);
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