move test to core

hooks/test/browser/combinations.test.js

@@ -477,45 +477,4 @@ describe('combinations', () => {
 			'anchor effect'
 		]);
 	});
-
-	it('should not crash or repeatedly add the same child when replacing a matched vnode with null', () => {
-		const B = () => <div>B</div>;
-
-		let update;
-		const Test = () => {
-			const [state, setState] = useState(true);
-			update = () => setState(s => !s);
-
-			if (state) {
-				return (
-					<div>
-						<B />
-						<div />
-					</div>
-				);
-			}
-			return (
-				<div>
-					<div />
-					{null}
-					<B />
-				</div>
-			);
-		};
-
-		render(<Test />, scratch);
-		expect(scratch.innerHTML).to.equal('<div><div>B</div><div></div></div>');
-
-		update();
-		rerender();
-		expect(scratch.innerHTML).to.equal('<div><div></div><div>B</div></div>');
-
-		update();
-		rerender();
-		expect(scratch.innerHTML).to.equal('<div><div>B</div><div></div></div>');
-
-		update();
-		rerender();
-		expect(scratch.innerHTML).to.equal('<div><div></div><div>B</div></div>');
-	});
 });

src/diff/children.js

@@ -234,7 +234,7 @@ function constructNewChildrenArray(newParentVNode, renderResult, oldChildren) {
 				oldVNode &&
 				oldVNode.key == null &&
 				oldVNode._dom &&
-				!oldVNode._flags & MATCHED
+				(oldVNode._flags & MATCHED) === 0
 			) {
 				if (oldVNode._dom == newParentVNode._nextDom) {
 					newParentVNode._nextDom = getDomSibling(oldVNode);

test/browser/render.test.js

@@ -1308,4 +1308,52 @@ describe('render()', () => {
 		expect(divs[1].hasAttribute('role')).to.equal(false);
 		expect(divs[2].hasAttribute('role')).to.equal(false);
 	});
+
+	it('should not crash or repeatedly add the same child when replacing a matched vnode with null', () => {
+		const B = () => <div>B</div>;
+
+		let update;
+		class App extends Component {
+			constructor(props) {
+				super(props);
+				this.state = { show: true };
+				update = () => {
+					this.setState(state => ({ show: !state.show }));
+				};
+			}
+
+			render() {
+				if (this.state.show) {
+					return (
+						<div>
+							<B />
+							<div />
+						</div>
+					);
+				}
+				return (
+					<div>
+						<div />
+						{null}
+						<B />
+					</div>
+				);
+			}
+		}
+
+		render(<App />, scratch);
+		expect(scratch.innerHTML).to.equal('<div><div>B</div><div></div></div>');
+
+		update();
+		rerender();
+		expect(scratch.innerHTML).to.equal('<div><div></div><div>B</div></div>');
+
+		update();
+		rerender();
+		expect(scratch.innerHTML).to.equal('<div><div>B</div><div></div></div>');
+
+		update();
+		rerender();
+		expect(scratch.innerHTML).to.equal('<div><div></div><div>B</div></div>');
+	});
 });