Fix missing context with contextType for class components (#122)

Author: w4zZz4p

src/index.js

@@ -92,14 +92,18 @@ function renderToString(vnode, context, opts, inner, isSvgMode, selectValue) {
 			}
 			else {
 				// class-based components
+				let cxType = nodeName.contextType;
+				let provider = cxType && context[cxType.__c];
+				let cctx = cxType != null ? (provider ? provider.props.value : cxType._defaultValue) : context;
+
 				// c = new nodeName(props, context);
-				c = vnode.__c = new nodeName(props, context);
+				c = vnode.__c = new nodeName(props, cctx);
 				c.__v = vnode;
 				// turn off stateful re-rendering:
 				c._dirty = c.__d = true;
 				c.props = props;
 				if (c.state==null) c.state = {};
-				c.context = context;
+				c.context = cctx;
 				if (nodeName.getDerivedStateFromProps) c.state = assign(assign({}, c.state), nodeName.getDerivedStateFromProps(c.props, c.state));
 				else if (c.componentWillMount) c.componentWillMount();
 				rendered = c.render(c.props, c.state, c.context);

test/context.js

@@ -1,5 +1,5 @@
 import render from '../src/jsx';
-import { h, createContext } from 'preact';
+import { h, createContext, Component } from 'preact';
 import chai, { expect } from 'chai';
 import sinonChai from 'sinon-chai';
 chai.use(sinonChai);
@@ -12,6 +12,32 @@ function dedent([str]) {
 describe('context', () => {
 	let renderJsx = (jsx, opts) => render(jsx, null, opts).replace(/ {2}/g, '\t');
 
+	it('should support class component as consumer', () => {
+		const Ctx = createContext();
+
+		class ClassConsumer extends Component {
+			render() {
+				const value = this.context;
+				return (
+				    <section>
+                        value is: {value}
+					</section>
+				);
+			}
+		}
+		ClassConsumer.contextType = Ctx;
+
+		let rendered = renderJsx(
+			<Ctx.Provider value="correct">
+				<ClassConsumer />
+			</Ctx.Provider>
+		);
+
+		expect(rendered).to.equal(dedent`
+			<section>value is: correct</section>
+		`);
+	});
+
 	it('should support createContext', () => {
 		const { Provider, Consumer } = createContext();
 		let rendered = renderJsx(