Only run propType checks on createElement & cloneElement not on every render.

src/index.js

@@ -293,7 +293,7 @@ function normalizeVNode(vnode) {
 	}
 
 	applyEventNormalization(vnode);
-
+	validatePropTypes(vnode);
 	return vnode;
 }
 
@@ -318,6 +318,28 @@ function cloneElement(element, props, ...children) {
 	return normalizeVNode(preactCloneElement(...cloneArgs));
 }
 
+function validatePropTypes (vnode) {
+	let componentClass = typeof vnode.nodeName === 'function' ? vnode.nodeName : vnode.type;
+
+	if (typeof componentClass !== 'function') return;
+	let name = (
+		componentClass.prototype.displayName
+		|| componentClass.displayName
+		|| componentClass.name
+	);
+
+	let propTypes = componentClass.propTypes;
+
+	if (propTypes) {
+		let props = vnode.props;
+		for (let propKey in propTypes) {
+			if (propTypes.hasOwnProperty(propKey) && typeof propTypes[propKey] === 'function') {
+				let err = propTypes[propKey](props, propKey, name, 'prop');
+				if (err) console.error(new Error(err.message || err));
+			}
+		}
+	}
+}
 
 function isValidElement(element) {
 	return element && ((element instanceof VNode) || element.$$typeof===REACT_ELEMENT_TYPE);
@@ -509,21 +531,6 @@ function propsHook(props, context) {
 			props.children[0] = props.children;
 		}
 	}
-
-	// add proptype checking
-	if (DEV) {
-		let ctor = typeof this==='function' ? this : this.constructor,
-			propTypes = this.propTypes || ctor.propTypes;
-		if (propTypes) {
-			for (let prop in propTypes) {
-				if (propTypes.hasOwnProperty(prop) && typeof propTypes[prop]==='function') {
-					const displayName = this.displayName || ctor.name;
-					let err = propTypes[prop](props, prop, displayName, 'prop');
-					if (err) console.error(new Error(err.message || err));
-				}
-			}
-		}
-	}
 }
 
 

test/component.js

@@ -236,6 +236,28 @@ describe('components', () => {
 			};
 			checkPropTypes(Foo2);
 		});
+
+		it.only('should handle function as children propTypes', () => {
+			function Foo (props) { return React.Children.only(props.children)(); }
+
+			Foo.propTypes = {
+				children: React.PropTypes.func.isRequired
+			};
+
+			sinon.stub(console, 'error');
+
+			React.render(<Foo/>, scratch);
+			expect(console.error).to.have.been.calledWithMatch({
+				message: 'Children.only() expects only one child.'
+			});
+
+			console.error.reset();
+
+			React.render(<Foo>{() => <div/>}</Foo>, scratch);
+			expect(console.error).not.to.have.been.called;
+
+			console.error.restore();
+		});
 	});
 
 	describe("mixins", () => {