(fix) - minor corrections for diffing tests

debug/test/browser/debug.test.js

@@ -189,17 +189,6 @@ describe('debug', () => {
 		expect(fn).to.throw(/createElement/);
 	});
 
-	it('should throw errors when accessing certain attributes', () => {
-		const vnode = h('div', null);
-		expect(() => vnode).to.not.throw();
-		expect(() => vnode.attributes).to.throw(/use vnode.props/);
-		expect(() => vnode.nodeName).to.throw(/use vnode.type/);
-		expect(() => vnode.children).to.throw(/use vnode.props.children/);
-		expect(() => vnode.attributes = {}).to.throw(/use vnode.props/);
-		expect(() => vnode.nodeName = 'test').to.throw(/use vnode.type/);
-		expect(() => vnode.children = [<div />]).to.throw(/use vnode.props.children/);
-	});
-
 	it('should print an error when component is an array', () => {
 		let fn = () => render(h([<div />]), scratch);
 		expect(fn).to.throw(/createElement/);

src/component.js

@@ -13,6 +13,7 @@ import { Fragment } from './create-element';
 export function Component(props, context) {
 	this.props = props;
 	this.context = context;
+	if (this.state==null) this.state = {};
 	// this.constructor // When component is functional component, this is reset to functional component
 	// if (this.state==null) this.state = {};
 	// this.state = {};
@@ -38,9 +39,9 @@ export function Component(props, context) {
  * updated
  */
 Component.prototype.setState = function(update, callback) {
+	if (this.state) this._prevState = this.state;
 	// only clone state when copying to nextState the first time.
 	let s = (this._nextState!==this.state && this._nextState) || (this._nextState = assign({}, this.state));
-
 	// if update() mutates state in-place, skip the copy:
 	if (typeof update!=='function' || (update = update(s, this.props))) {
 		assign(s, update);
@@ -51,7 +52,6 @@ Component.prototype.setState = function(update, callback) {
 
 	if (this._vnode) {
 		if (callback) this._renderCallbacks.push(callback);
-		if (this.state) this._prevState = this.state;
 		enqueueRender(this);
 	}
 };

src/diff/index.js

@@ -71,6 +71,7 @@ export function diff(parentDom, newVNode, oldVNode, context, isSvg, excessDomChi
 				c._nextState = c.state;
 			}
 			if (newType.getDerivedStateFromProps!=null) {
+				c._prevState = c.state;
 				assign(c._nextState==c.state ? (c._nextState = assign({}, c._nextState)) : c._nextState, newType.getDerivedStateFromProps(newProps, c._nextState));
 			}
 
@@ -100,7 +101,7 @@ export function diff(parentDom, newVNode, oldVNode, context, isSvg, excessDomChi
 			}
 
 			oldProps = c.props;
-			oldState = c._prevState;
+			oldState = c._prevState || {};
 
 			c.context = cctx;
 			c.props = newProps;