(fix) - nested setState calls with accurate this.state

src/diff/index.js

@@ -132,7 +132,10 @@ export function diff(parentDom, newVNode, oldVNode, context, isSvg, excessDomChi
 
 			c.base = newVNode._dom;
 
-			while (tmp=c._renderCallbacks.pop()) tmp.call(c);
+			while (tmp=c._renderCallbacks.pop()) {
+				if (c._nextState) { c.state = c._nextState; }
+				tmp.call(c);
+			}
 
 			// Don't call componentDidUpdate on mount or when we bailed out via
 			// `shouldComponentUpdate`

test/browser/components.test.js

@@ -132,6 +132,42 @@ describe('Components', () => {
 			expect(spy).to.not.be.called;
 		});
 
+		it('should accurately call nested setState callbacks', () => {
+			let states = [];
+			let finalState;
+			class Foo extends Component {
+				constructor(props) {
+					super(props);
+					this.state = { a: 'b' };
+				}
+
+				componentDidMount() {
+					states.push(this.state);
+					// eslint-disable-next-line
+					this.setState({ a: 'a' }, () => {
+						states.push(this.state);
+						this.setState({ a: 'c' }, () => {
+							states.push(this.state);
+						});
+					});
+				}
+
+				render() {
+					finalState = this.state;
+					return <p>Test</p>;
+				}
+			}
+
+			render(<Foo />, scratch);
+			rerender();
+
+			let [firstState, secondState, thirdState] = states;
+			expect(finalState).to.deep.equal({ a: 'c' });
+			expect(firstState).to.deep.equal({ a: 'b' });
+			expect(secondState).to.deep.equal({ a: 'a' });
+			expect(thirdState).to.deep.equal({ a: 'c' });
+		});
+
 		it('should initialize props & context but not state in Component constructor', () => {
 			// Not initializing state matches React behavior: https://codesandbox.io/s/rml19v8o2q
 			class Foo extends Component {