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Do not unmount layout effects on initial Offscreen mount #25592

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merged 5 commits into from
Nov 1, 2022
Merged

Do not unmount layout effects on initial Offscreen mount #25592

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804f3c7
Do not unmount layout effects on initial Offscreen mount
sammy-SC Oct 31, 2022
8eee696
Add unit test for the edge case
sammy-SC Oct 31, 2022
3e65e5a
Add comment to explain the unit test
sammy-SC Oct 31, 2022
838a7af
prettier
sammy-SC Oct 31, 2022
30f1466
Add comment and make the condition more obvious
sammy-SC Nov 1, 2022
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2 changes: 1 addition & 1 deletion packages/react-reconciler/src/ReactFiberCommitWork.new.js
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Expand Up @@ -2880,7 +2880,7 @@ function commitMutationEffectsOnFiber(
}

if (isHidden) {
if (!wasHidden) {
if (current !== null && current.memoizedState === null) {
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@philIip philIip Oct 31, 2022 •
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so my understanding is that the issue is happening bc when the hidden offscreen component is mounted, we are not running layout effects.

conceptually, why would we want to run layout effects if the component is hidden? what is the example of breaking behavior?

also it is kinda confusing so i think we should rename this or add a comment explaining what the actual behavior is (i.e. neverVisible) or sth like that

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so my understanding is that the issue is happening bc when the hidden offscreen component is mounted, we are not running layout effects.

The issue is that layout effects are cleaned up even when Offscreen is hidden. If you look at the test, it may happen when two OffScreens are nested (keep in mind every Suspense boundary uses Offscreen).

if ((offscreenBoundary.mode & ConcurrentMode) !== NoMode) {
// Disappear the layout effects of all the children
recursivelyTraverseDisappearLayoutEffects(offscreenBoundary);
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2 changes: 1 addition & 1 deletion packages/react-reconciler/src/ReactFiberCommitWork.old.js
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Expand Up @@ -2880,7 +2880,7 @@ function commitMutationEffectsOnFiber(
}

if (isHidden) {
if (!wasHidden) {
if (current !== null && current.memoizedState === null) {
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if ((offscreenBoundary.mode & ConcurrentMode) !== NoMode) {
// Disappear the layout effects of all the children
recursivelyTraverseDisappearLayoutEffects(offscreenBoundary);
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38 changes: 38 additions & 0 deletions packages/react-reconciler/src/__tests__/ReactOffscreen-test.js
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Expand Up @@ -268,6 +268,44 @@ describe('ReactOffscreen', () => {
expect(root).toMatchRenderedOutput(<span prop="Child" />);
});

// @gate enableOffscreen
it('nested offscreen does not call componentWillUnmount when hidden', async () => {
// This is a bug that appeared during production test of <unstable_Offscreen />.
// It is a very specific scenario with nested Offscreens. The inner offscreen
// goes from visible to hidden in synchronous update.
class ClassComponent extends React.Component {
render() {
return <Text text="Child" />;
}

componentWillUnmount() {
Scheduler.unstable_yieldValue('componentWillUnmount');
}
}

function App() {
const [isVisible, setIsVisible] = React.useState(true);

if (isVisible === true) {
setIsVisible(false);
}

return (
<Offscreen mode="hidden">
<Offscreen mode={isVisible ? 'visible' : 'hidden'}>
<ClassComponent />
</Offscreen>
</Offscreen>
);
}

const root = ReactNoop.createRoot();
await act(async () => {
root.render(<App />);
});
expect(Scheduler).toHaveYielded(['Child']);
});

// @gate enableOffscreen
it('mounts/unmounts layout effects when visibility changes (starting hidden)', async () => {
function Child({text}) {
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