implement event modifiers

src/compile/nodes/Attribute.ts

@@ -17,6 +17,7 @@ export default class Attribute extends Node {
 	isSpread: boolean;
 	isTrue: boolean;
 	isDynamic: boolean;
+	isStatic: boolean;
 	isSynthetic: boolean;
 	shouldCache: boolean;
 	expression?: Expression;
@@ -37,12 +38,14 @@ export default class Attribute extends Node {
 			this.chunks = null;
 
 			this.isDynamic = true; // TODO not necessarily
+			this.isStatic = false;
 			this.shouldCache = false; // TODO does this mean anything here?
 		}
 
 		else {
 			this.name = info.name;
 			this.isTrue = info.value === true;
+			this.isStatic = true;
 			this.isSynthetic = info.synthetic;
 
 			this.dependencies = new Set();
@@ -52,6 +55,8 @@ export default class Attribute extends Node {
 				: info.value.map(node => {
 					if (node.type === 'Text') return node;
 
+					this.isStatic = false;
+
 					const expression = new Expression(component, this, scope, node.expression);
 
 					addToSet(this.dependencies, expression.dynamic_dependencies);

src/compile/nodes/Element.ts

@@ -337,7 +337,7 @@ export default class Element extends Node {
 			}
 
 			if (name === 'slot') {
-				if (attribute.isDynamic) {
+				if (!attribute.isStatic) {
 					component.error(attribute, {
 						code: `invalid-slot-attribute`,
 						message: `slot attribute cannot have a dynamic value`
@@ -425,7 +425,7 @@ export default class Element extends Node {
 
 			if (!attribute) return null;
 
-			if (attribute.isDynamic) {
+			if (!attribute.isStatic) {
 				component.error(attribute, {
 					code: `invalid-type`,
 					message: `'type' attribute cannot be dynamic if input uses two-way binding`
@@ -464,7 +464,7 @@ export default class Element extends Node {
 						(attribute: Attribute) => attribute.name === 'multiple'
 					);
 
-					if (attribute && attribute.isDynamic) {
+					if (attribute && !attribute.isStatic) {
 						component.error(attribute, {
 							code: `dynamic-multiple-attribute`,
 							message: `'multiple' attribute cannot be dynamic if select uses two-way binding`

src/compile/render-dom/wrappers/shared/addEventHandlers.ts

@@ -7,14 +7,12 @@ export default function addEventHandlers(
 	handlers: EventHandler[]
 ) {
 	handlers.forEach(handler => {
-		const modifiers = [];
-		if (handler.modifiers.has('preventDefault')) modifiers.push('event.preventDefault();');
-		if (handler.modifiers.has('stopPropagation')) modifiers.push('event.stopPropagation();');
+		let snippet = handler.render();
+		if (handler.modifiers.has('preventDefault')) snippet = `@preventDefault(${snippet})`;
+		if (handler.modifiers.has('stopPropagation')) snippet = `@stopPropagation(${snippet})`;
 
 		const opts = ['passive', 'once', 'capture'].filter(mod => handler.modifiers.has(mod));
 
-		const snippet = handler.render();
-
 		if (opts.length) {
 			const optString = (opts.length === 1 && opts[0] === 'capture')
 				? 'true'

src/internal/dom.js

@@ -78,6 +78,20 @@ export function addListener(node, event, handler, options) {
 	return () => node.removeEventListener(event, handler, options);
 }
 
+export function preventDefault(fn) {
+	return function(event) {
+		event.preventDefault();
+		return fn.call(this, event);
+	};
+}
+
+export function stopPropagation(fn) {
+	return function(event) {
+		event.stopPropagation();
+		return fn.call(this, event);
+	};
+}
+
 export function setAttribute(node, attribute, value) {
 	if (value == null) node.removeAttribute(attribute);
 	else node.setAttribute(attribute, value);

test/js/samples/event-modifiers/expected.js

@@ -1,15 +1,9 @@
 /* generated by Svelte vX.Y.Z-alpha1 */
-import { SvelteComponent as SvelteComponent_1, addListener, append, createElement, createText, detachNode, init, insert, noop, run, run_all, safe_not_equal } from "svelte/internal.js";
+import { SvelteComponent as SvelteComponent_1, addListener, append, createElement, createText, detachNode, init, insert, noop, preventDefault, run, run_all, safe_not_equal, stopPropagation } from "svelte/internal.js";
 
 function create_fragment(component, ctx) {
 	var div, button0, text1, button1, text3, button2, current, dispose;
 
-	function click_handler(event) {
-		event.stopPropagation();
-		event.preventDefault();
-		handleClick(event);
-	}
-
 	return {
 		c() {
 			div = createElement("div");
@@ -22,7 +16,7 @@ function create_fragment(component, ctx) {
 			button2 = createElement("button");
 			button2.textContent = "or me!";
 			dispose = [
-				addListener(button0, click_handler),
+				addListener(button0, "click", stopPropagation(preventDefault(handleClick))),
 				addListener(button1, "click", handleClick, { once: true, capture: true }),
 				addListener(button2, "click", handleClick, true),
 				addListener(div, "touchstart", handleTouchstart, { passive: true })

test/runtime/samples/event-handler-modifier-once/_config.js

@@ -0,0 +1,16 @@
+export default {
+	html: `
+		<button>0</button>
+	`,
+
+	async test({ assert, component, target, window }) {
+		const button = target.querySelector('button');
+		const event = new window.MouseEvent('click');
+
+		await button.dispatchEvent(event);
+		assert.equal(component.count, 1);
+
+		await button.dispatchEvent(event);
+		assert.equal(component.count, 1);
+	}
+};

test/runtime/samples/event-handler-modifier-once/main.html

@@ -0,0 +1,5 @@
+<script>
+	export let count = 0;
+</script>
+
+<button on:click|once="{() => count += 1}">{count}</button>

test/runtime/samples/event-handler-modifier-prevent-default/_config.js

@@ -0,0 +1,16 @@
+export default {
+	html: `
+		<button>click me</button>
+	`,
+
+	async test({ assert, component, target, window }) {
+		const button = target.querySelector('button');
+		const event = new window.MouseEvent('click', {
+			cancelable: true
+		});
+
+		await button.dispatchEvent(event);
+
+		assert.ok(component.default_was_prevented);
+	}
+};

test/runtime/samples/event-handler-modifier-prevent-default/main.html

@@ -0,0 +1,9 @@
+<script>
+	export let default_was_prevented;
+
+	function handle_click(event) {
+		default_was_prevented = event.defaultPrevented;
+	}
+</script>
+
+<button on:click|preventDefault={handle_click}>click me</button>

test/runtime/samples/event-handler-modifier-stop-propagation/_config.js

@@ -0,0 +1,19 @@
+export default {
+	html: `
+		<div>
+			<button>click me</button>
+		</div>
+	`,
+
+	async test({ assert, component, target, window }) {
+		const button = target.querySelector('button');
+		const event = new window.MouseEvent('click', {
+			bubbles: true
+		});
+
+		await button.dispatchEvent(event);
+
+		assert.ok(component.inner_clicked);
+		assert.ok(!component.outer_clicked);
+	}
+};

test/runtime/samples/event-handler-modifier-stop-propagation/main.html

@@ -0,0 +1,16 @@
+<script>
+	export let inner_clicked;
+	export let outer_clicked;
+
+	function handle_inner_click(event) {
+		inner_clicked = true;
+	}
+
+	function handle_outer_click(event) {
+		outer_clicked = true;
+	}
+</script>
+
+<div on:click={handle_outer_click}>
+	<button on:click|stopPropagation={handle_inner_click}>click me</button>
+</div>