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Make undefined return value invariant a warning for memo and forwardRef #19575

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Make undefined return value invariant a warning for memo and forwardRef #19575

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6 changes: 2 additions & 4 deletions packages/react-dom/src/__tests__/ReactEmptyComponent-test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -323,9 +323,7 @@ describe('ReactEmptyComponent', () => {

expect(() => {
ReactTestUtils.renderIntoDocument(<EmptyForwardRef />);
}).toThrowError(
'ForwardRef(Empty)(...): Nothing was returned from render.',
);
}).toWarnDev('ForwardRef(Empty)(...): Nothing was returned from render.');
});

it('should warn about React.memo that returns undefined', () => {
Expand All @@ -334,6 +332,6 @@ describe('ReactEmptyComponent', () => {

expect(() => {
ReactTestUtils.renderIntoDocument(<EmptyMemo />);
}).toThrowError('Empty(...): Nothing was returned from render.');
}).toWarnDev('Empty(...): Nothing was returned from render.');
});
});
17 changes: 13 additions & 4 deletions packages/react-reconciler/src/ReactChildFiber.new.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1383,6 +1383,18 @@ function ChildReconciler(shouldTrackSideEffects) {
// component, throw an error. If Fiber return types are disabled,
// we already threw above.
switch (returnFiber.tag) {
case Block:
case ForwardRef:
case SimpleMemoComponent:
if (__DEV__) {
console.warn(
'%s(...): Nothing was returned from render. This usually means a ' +
'return statement is missing. Or, to render nothing, ' +
'return null.',
getComponentName(returnFiber.type) || 'Component',
);
}
break;
case ClassComponent: {
if (__DEV__) {
const instance = returnFiber.stateNode;
Expand All @@ -1395,10 +1407,7 @@ function ChildReconciler(shouldTrackSideEffects) {
// Intentionally fall through to the next case, which handles both
// functions and classes
// eslint-disable-next-lined no-fallthrough
case Block:
case FunctionComponent:
case ForwardRef:
case SimpleMemoComponent: {
case FunctionComponent: {
invariant(
false,
'%s(...): Nothing was returned from render. This usually means a ' +
Expand Down
17 changes: 13 additions & 4 deletions packages/react-reconciler/src/ReactChildFiber.old.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1375,6 +1375,18 @@ function ChildReconciler(shouldTrackSideEffects) {
// component, throw an error. If Fiber return types are disabled,
// we already threw above.
switch (returnFiber.tag) {
case Block:
case ForwardRef:
case SimpleMemoComponent:
if (__DEV__) {
console.warn(
'%s(...): Nothing was returned from render. This usually means a ' +
'return statement is missing. Or, to render nothing, ' +
'return null.',
getComponentName(returnFiber.type) || 'Component',
);
}
break;
case ClassComponent: {
if (__DEV__) {
const instance = returnFiber.stateNode;
Expand All @@ -1387,10 +1399,7 @@ function ChildReconciler(shouldTrackSideEffects) {
// Intentionally fall through to the next case, which handles both
// functions and classes
// eslint-disable-next-lined no-fallthrough
case Block:
case FunctionComponent:
case ForwardRef:
case SimpleMemoComponent: {
case FunctionComponent: {
invariant(
false,
'%s(...): Nothing was returned from render. This usually means a ' +
Expand Down