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More useful DEV error message when lazy-rendering Context Provider #27168

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More useful DEV error message when lazy-rendering Context Provider #27168

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19 changes: 12 additions & 7 deletions packages/react-reconciler/src/ReactFiberBeginWork.js
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Original file line number Diff line number Diff line change
Expand Up @@ -116,7 +116,11 @@ import shallowEqual from 'shared/shallowEqual';
import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
import getComponentNameFromType from 'shared/getComponentNameFromType';
import ReactStrictModeWarnings from './ReactStrictModeWarnings';
import {REACT_LAZY_TYPE, getIteratorFn} from 'shared/ReactSymbols';
import {
REACT_LAZY_TYPE,
REACT_PROVIDER_TYPE,
getIteratorFn,
} from 'shared/ReactSymbols';
import {
getCurrentFiberOwnerNameInDevOrNull,
setIsRendering,
Expand Down Expand Up @@ -1831,12 +1835,13 @@ function mountLazyComponent(
}
let hint = '';
if (__DEV__) {
if (
Component !== null &&
typeof Component === 'object' &&
Component.$$typeof === REACT_LAZY_TYPE
) {
hint = ' Did you wrap a component in React.lazy() more than once?';
if (Component !== null && typeof Component === 'object') {
if (Component.$$typeof === REACT_LAZY_TYPE) {
hint = ' Did you wrap a component in React.lazy() more than once?';
} else if (Component.type.$$typeof === REACT_PROVIDER_TYPE) {
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@markspolakovs markspolakovs Aug 15, 2023

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Suggested change
} else if (Component.type.$$typeof === REACT_PROVIDER_TYPE) {
} else if (Component.type?.$$typeof === REACT_PROVIDER_TYPE) {

Defensive optional chaining in case Component.type doesn't exist

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@markspolakovs markspolakovs Dec 30, 2023

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This seems to fail the tests

hint =
' Context Providers cannot be lazily rendered without being wrapped in a component.';
}
}
}

Expand Down
31 changes: 31 additions & 0 deletions packages/react-reconciler/src/__tests__/ReactLazy-test.internal.js
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Expand Up @@ -783,6 +783,37 @@ describe('ReactLazy', () => {
);
});

it('throws with a useful error when rendering a context Provider', async () => {
const ctx = React.createContext(null);
const Provider = <ctx.Provider value={{}} />;
const BadLazy = lazy(() => fakeImport(Provider));

const root = ReactTestRenderer.create(
<Suspense fallback={<Text text="Loading..." />}>
<BadLazy />
</Suspense>,
{
unstable_isConcurrent: true,
},
);

await waitForAll(['Loading...']);

await resolveFakeImport(Provider);
root.update(
<Suspense fallback={<Text text="Loading..." />}>
<BadLazy />
</Suspense>,
);
await waitForThrow(
'Element type is invalid. Received a promise that resolves to: [object Object]. ' +
'Lazy element type must resolve to a class or function.' +
(__DEV__
? ' Context Providers cannot be lazily rendered without being wrapped in a component.'
: ''),
);
});

it('warns about defining propTypes on the outer wrapper', () => {
const LazyText = lazy(() => fakeImport(Text));
expect(() => {
Expand Down