Fix cascading renders with signals (#4966) (#4969)

Author: JoviDeCroock

hooks/test/browser/useState.test.jsx

@@ -17,6 +17,7 @@ describe('useState', () => {
 	});
 
 	afterEach(() => {
+		Component.prototype.shouldComponentUpdate = undefined;
 		teardown(scratch);
 	});
 
@@ -476,4 +477,64 @@ describe('useState', () => {
 			expect(renders).to.equal(2);
 		});
 	});
+
+	it('Works when we combine strict equality, signals bail and state settling', () => {
+		// In signals we bail when we are using no signals/computeds/....
+		Component.prototype.shouldComponentUpdate = function (
+			nextProps,
+			nextState
+		) {
+			return false;
+		};
+		let setA, setB;
+
+		const fooContext = createContext();
+		const barContext = createContext();
+
+		function FooProvider({ children }) {
+			const [a, _setA] = useState(0);
+			setA = _setA;
+			return <fooContext.Provider value={a}>{children}</fooContext.Provider>;
+		}
+
+		function BarProvider({ children }) {
+			const [b, _setB] = useState(0);
+			setB = _setB;
+			return <barContext.Provider value={b}>{children}</barContext.Provider>;
+		}
+
+		function Child() {
+			const a = useContext(fooContext);
+			const b = useContext(barContext);
+			return (
+				<p>
+					{a}-{b}
+				</p>
+			);
+		}
+
+		function App() {
+			return (
+				<FooProvider>
+					<BarProvider>
+						<Child />
+					</BarProvider>
+				</FooProvider>
+			);
+		}
+
+		render(<App />, scratch);
+		expect(scratch.innerHTML).to.equal('<p>0-0</p>');
+
+		act(() => {
+			// We update A first so that we have a top-down render going on
+			setA(1);
+			// The update will bail at B, we don't want sCU to run because
+			// else we risk the state's _nextValue being settled too early
+			// and thus applying the update too early and bailing on the subsequent
+			// render due to the values already being applied.
+			setB(1);
+		});
+		expect(scratch.innerHTML).to.equal('<p>1-1</p>');
+	});
 });

src/diff/index.js

@@ -183,14 +183,14 @@ export function diff(
 				}
 
 				if (
+					newVNode._original == oldVNode._original ||
 					(!(c._bits & COMPONENT_FORCE) &&
 						c.shouldComponentUpdate != NULL &&
 						c.shouldComponentUpdate(
 							newProps,
 							c._nextState,
 							componentContext
-						) === false) ||
-					newVNode._original == oldVNode._original
+						) === false)
 				) {
 					// More info about this here: https://gist.github.com/JoviDeCroock/bec5f2ce93544d2e6070ef8e0036e4e8
 					if (newVNode._original != oldVNode._original) {