Warn about undefined return value for memo and forwardRef (#19550)

Author: Brian Vaughn

packages/react-dom/src/__tests__/ReactEmptyComponent-test.js

@@ -316,4 +316,24 @@ describe('ReactEmptyComponent', () => {
 constnoscript2=container.firstChild;
 expect(noscript2).toBe(null);
 });
+
+it('should warn about React.forwardRef that returns undefined',()=>{
+constEmpty=()=>{};
+constEmptyForwardRef=React.forwardRef(Empty);
+
+expect(()=>{
+ReactTestUtils.renderIntoDocument(<EmptyForwardRef/>);
+}).toThrowError(
+'ForwardRef(Empty)(...): Nothing was returned from render.',
+);
+});
+
+it('should warn about React.memo that returns undefined',()=>{
+constEmpty=()=>{};
+constEmptyMemo=React.memo(Empty);
+
+expect(()=>{
+ReactTestUtils.renderIntoDocument(<EmptyMemo/>);
+}).toThrowError('Empty(...): Nothing was returned from render.');
+});
 });

packages/react-reconciler/src/ReactChildFiber.new.js

@@ -29,7 +29,9 @@ import {
 ClassComponent,
 HostText,
 HostPortal,
+ForwardRef,
 Fragment,
+SimpleMemoComponent,
 Block,
 }from'./ReactWorkTags';
 importinvariantfrom'shared/invariant';
@@ -1393,14 +1395,16 @@ function ChildReconciler(shouldTrackSideEffects) {
 // Intentionally fall through to the next case, which handles both
 // functions and classes
 // eslint-disable-next-lined no-fallthrough
-caseFunctionComponent: {
-constComponent=returnFiber.type;
+caseBlock:
+caseFunctionComponent:
+caseForwardRef:
+caseSimpleMemoComponent: {
 invariant(
 false,
 '%s(...): Nothing was returned from render. This usually means a '+
 'return statement is missing. Or, to render nothing, '+
 'return null.',
-Component.displayName||Component.name||'Component',
+getComponentName(returnFiber.type)||'Component',
 );
 }
 }

packages/react-reconciler/src/ReactChildFiber.old.js

@@ -29,7 +29,9 @@ import {
 ClassComponent,
 HostText,
 HostPortal,
+ForwardRef,
 Fragment,
+SimpleMemoComponent,
 Block,
 }from'./ReactWorkTags';
 importinvariantfrom'shared/invariant';
@@ -1385,14 +1387,16 @@ function ChildReconciler(shouldTrackSideEffects) {
 // Intentionally fall through to the next case, which handles both
 // functions and classes
 // eslint-disable-next-lined no-fallthrough
-caseFunctionComponent: {
-constComponent=returnFiber.type;
+caseBlock:
+caseFunctionComponent:
+caseForwardRef:
+caseSimpleMemoComponent: {
 invariant(
 false,
 '%s(...): Nothing was returned from render. This usually means a '+
 'return statement is missing. Or, to render nothing, '+
 'return null.',
-Component.displayName||Component.name||'Component',
+getComponentName(returnFiber.type)||'Component',
 );
 }
 }