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Don’t error when returning an empty Fragment #12966

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merged 4 commits into from Jun 11, 2018
Merged

Don’t error when returning an empty Fragment #12966

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931bc7d
Don’t error when returning an empty Fragment
philipp-spiess Jun 2, 2018
4de2539
Test the update path as well
philipp-spiess Jun 2, 2018
697bd71
Reuse existing code path
gaearon Jun 11, 2018
6d8c3f5
An even more explicit solution that also fixes Flow
gaearon Jun 11, 2018
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12 changes: 12 additions & 0 deletions packages/react-dom/src/__tests__/ReactDOMFiber-test.js
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Expand Up @@ -171,6 +171,18 @@ describe('ReactDOMFiber', () => {
expect(firstNode.tagName).toBe('DIV');
});

it('renders an empty fragment', () => {
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No idea if that is the right place for the test :)

const EmptyFragment = () => <React.Fragment />;

let instance = null;
ReactDOM.render(<EmptyFragment />, container);

expect(container.childNodes.length).toBe(0);

const firstNode = ReactDOM.findDOMNode(instance);
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You can just check container.firstChild?

expect(firstNode).toBe(null);
});

let svgEls, htmlEls, mathEls;
const expectSVG = {ref: el => svgEls.push(el)};
const expectHTML = {ref: el => htmlEls.push(el)};
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6 changes: 6 additions & 0 deletions packages/react-reconciler/src/ReactChildFiber.js
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Expand Up @@ -1215,6 +1215,12 @@ function ChildReconciler(shouldTrackSideEffects) {
newChild.key === null
) {
newChild = newChild.props.children;

// In case of an empty fragment, this is undefined. Since we crash when
// undefined is reconciled, we bail out early.
if (typeof newChild === 'undefined') {
return deleteRemainingChildren(returnFiber, currentFirstChild);
}
}

// Handle object types
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