Slight improvements to code coverage (preactjs#1558)

* Ignore dist folder

* Improve code coverage slightly

Author: marvinhagemeister

debug/src/debug.js

@@ -130,19 +130,19 @@ export function initDebug() {
 	options.diffed = (vnode) => {
 		if (vnode._component && vnode._component.__hooks) {
 			let hooks = vnode._component.__hooks;
-			if (hooks._list.length > 0) {
-				hooks._list.forEach(hook => {
-					if (hook._callback && (!hook._args || !Array.isArray(hook._args))) {
-						console.warn(
-							`In ${vnode.type.name || vnode.type} you are calling useMemo/useCallback without passing arguments.\n` +
-							`This is a noop since it will not be able to memoize, it will execute it every render.`
-						);
-					}
-				});
-			}
+			hooks._list.forEach(hook => {
+				if (hook._callback && (!hook._args || !Array.isArray(hook._args))) {
+					/* istanbul ignore next */
+					console.warn(
+						`In ${vnode.type.name || vnode.type} you are calling useMemo/useCallback without passing arguments.\n` +
+						`This is a noop since it will not be able to memoize, it will execute it every render.`
+					);
+				}
+			});
 			if (hooks._pendingEffects.length > 0) {
 				hooks._pendingEffects.forEach((effect) => {
 					if (!effect._args || !Array.isArray(effect._args)) {
+						/* istanbul ignore next */
 						throw new Error('You should provide an array of arguments as the second argument to the "useEffect" hook.\n\n' +
 							'Not doing so will invoke this effect on every render.\n\n' +
 							'This effect can be found in the render of ' + (vnode.type.name || vnode.type) + '.');
@@ -152,6 +152,7 @@ export function initDebug() {
 			if (hooks._pendingLayoutEffects.length > 0) {
 				hooks._pendingLayoutEffects.forEach((layoutEffect) => {
 					if (!layoutEffect._args || !Array.isArray(layoutEffect._args)) {
+						/* istanbul ignore next */
 						throw new Error('You should provide an array of arguments as the second argument to the "useEffect" hook.\n\n' +
 							'Not doing so will invoke this effect on every render.\n\n' +
 							'This effect can be found in the render of ' + (vnode.type.name || vnode.type) + '.');

debug/test/browser/debug.test.js

@@ -77,6 +77,11 @@ describe('debug', () => {
 		expect(fn).to.throw(/createElement/);
 	});
 
+	it('should print an error on invalid object component', () => {
+		let fn = () => render(h({}), scratch);
+		expect(fn).to.throw(/createElement/);
+	});
+
 	it('should throw an error when using a hook outside a render', () => {
 		class App extends Component {
 			componentWillMount() {
@@ -172,6 +177,15 @@ describe('debug', () => {
 		expect(warnings.length).to.equal(2);
 	});
 
+	it('should warn when non-array args is passed', () => {
+		const App = () => {
+			const foo = useMemo(() => 'foo', 12);
+			return <p>{foo}</p>;
+		};
+		render(<App />, scratch);
+		expect(warnings[0]).to.match(/without passing arguments/);
+	});
+
 	it('should print an error on invalid refs', () => {
 		let fn = () => render(<div ref="a" />, scratch);
 		expect(fn).to.throw(/createRef/);

hooks/src/index.js

@@ -201,6 +201,7 @@ export function useDebugValue(value, formatter) {
  * Invoke a component's pending effects after the next frame renders
  * @type {(component: import('./internal').Component) => void}
  */
+/* istanbul ignore next */
 let afterPaint = () => {};
 
 /**
@@ -219,6 +220,7 @@ function scheduleFlushAfterPaint() {
 	setTimeout(flushAfterPaintEffects, 0);
 }
 
+/* istanbul ignore else */
 if (typeof window !== 'undefined') {
 	afterPaint = (component) => {
 		if (!component._afterPaintQueued && (component._afterPaintQueued = true) && afterPaintEffects.push(component) === 1) {

hooks/test/browser/useImperativeHandle.test.js

@@ -49,4 +49,20 @@ describe('useImperativeHandle', () => {
 		expect(ref.current).to.have.property('test');
 		expect(ref.current.test()).to.equal('test1');
 	});
+
+	it('should not update ref when args have not changed', () => {
+		let ref;
+
+		function Comp() {
+			ref = useRef({});
+			useImperativeHandle(ref, () => ({ test: () => 'test' }), [1]);
+			return <p>Test</p>;
+		}
+
+		render(<Comp />, scratch);
+		expect(ref.current.test()).to.equal('test');
+
+		render(<Comp />, scratch);
+		expect(ref.current.test()).to.equal('test');
+	});
 });

karma.conf.js

@@ -134,6 +134,7 @@ module.exports = function(config) {
 									exclude: [
 										// Default config
 										'coverage/**',
+										'dist/**',
 										'test/**',
 										'test{,-*}.js',
 										'**/*.test.js',