Merge pull request preactjs#1584 from developit/fix/useState

(fix) - useState can potentially add to the state queue and make the _dirty call neglect this

hooks/test/browser/useState.test.js

@@ -129,4 +129,40 @@ describe('useState', () => {
 		rerender();
 		expect(scratch.textContent).to.include('Count: 10');
 	});
+
+	it('should handle queued useState', () => {
+		function Message({ message, onClose }) {
+			const [isVisible, setVisible] = useState(Boolean(message));
+			const [prevMessage, setPrevMessage] = useState(message);
+
+			if (message !== prevMessage) {
+				setPrevMessage(message);
+				setVisible(Boolean(message));
+			}
+
+			if (!isVisible) {
+				return null;
+			}
+			return <p onClick={onClose}>{message}</p>;
+		}
+
+		function App() {
+			const [message, setMessage] = useState('Click Here!!');
+			return (
+				<Message
+					onClose={() => {
+						setMessage('');
+					}}
+					message={message}
+				/>
+			);
+		}
+
+		render(<App />, scratch);
+		expect(scratch.textContent).to.equal('Click Here!!');
+		const text = scratch.querySelector('p');
+		text.click();
+		rerender();
+		expect(scratch.innerHTML).to.equal('');
+	});
 });

src/diff/index.js

@@ -139,8 +139,8 @@ export function diff(dom, parentDom, newVNode, oldVNode, context, isSvg, excessD
 			if (options.render) options.render(newVNode);
 
 			let prev = c._prevVNode || null;
-			let vnode = c._prevVNode = coerceToVNode(c.render(c.props, c.state, c.context));
 			c._dirty = false;
+			let vnode = c._prevVNode = coerceToVNode(c.render(c.props, c.state, c.context));
 
 			if (c.getChildContext!=null) {
 				context = assign(assign({}, context), c.getChildContext());