implement event modifiers

src/compile/nodes/Element.ts

@@ -595,12 +595,7 @@ export default class Element extends Node {
 
 				if (modifier === 'passive') {
 					if (passiveEvents.has(handler.name)) {
-						const usesEvent = (
+						if (!handler.usesEventObject) {
-							handler.callee.name === 'event' ||
-							handler.args.some(x => x.usesEvent)
-						);
-
-						if (!usesEvent) {
 							component.warn(handler, {
 								code: 'redundant-event-modifier',
 								message: `Touch event handlers that don't use the 'event' object are passive by default`
@@ -623,6 +618,11 @@ export default class Element extends Node {
 					});
 				}
 			});
+
+			if (passiveEvents.has(handler.name) && !handler.usesEventObject) {
+				// touch/wheel events should be passive by default
+				handler.modifiers.add('passive');
+			}
 		});
 	}
 

src/compile/nodes/EventHandler.ts

@@ -16,6 +16,7 @@ export default class EventHandler extends Node {
 
 	usesComponent: boolean;
 	usesContext: boolean;
+	usesEventObject: boolean;
 	isCustomEvent: boolean;
 	shouldHoist: boolean;
 
@@ -42,11 +43,13 @@ export default class EventHandler extends Node {
 
 			this.usesComponent = !validCalleeObjects.has(this.callee.name);
 			this.usesContext = false;
+			this.usesEventObject = this.callee.name === 'event';
 
 			this.args = info.expression.arguments.map(param => {
 				const expression = new Expression(component, this, scope, param);
 				addToSet(this.dependencies, expression.dependencies);
 				if (expression.usesContext) this.usesContext = true;
+				if (expression.usesEvent) this.usesEventObject = true;
 				return expression;
 			});
 
@@ -58,6 +61,7 @@ export default class EventHandler extends Node {
 			this.args = null;
 			this.usesComponent = true;
 			this.usesContext = false;
+			this.usesEventObject = true;
 
 			this.snippet = null; // TODO handle shorthand events here?
 		}

src/compile/render-dom/wrappers/Element/index.ts

@@ -649,8 +649,13 @@ export default class ElementWrapper extends Wrapper {
 					${handlerName}.destroy();
 				`);
 			} else {
+				const modifiers = [];
+				if (handler.modifiers.has('preventDefault')) modifiers.push('event.preventDefault();');
+				if (handler.modifiers.has('stopPropagation')) modifiers.push('event.stopPropagation();');
+
 				const handlerFunction = deindent`
 					function ${handlerName}(event) {
+						${modifiers}
 						${handlerBody}
 					}
 				`;
@@ -661,6 +666,20 @@ export default class ElementWrapper extends Wrapper {
 					block.builders.init.addBlock(handlerFunction);
 				}
 
+				const opts = ['passive', 'once', 'capture'].filter(mod => handler.modifiers.has(mod));
+				if (opts.length) {
+					const optString = (opts.length === 1 && opts[0] === 'capture')
+						? 'true'
+						: `{ ${opts.map(opt => `${opt}: true`).join(', ')} }`;
+
+					block.builders.hydrate.addLine(
+						`@addListener(${this.var}, "${handler.name}", ${handlerName}, ${optString});`
+					);
+
+					block.builders.destroy.addLine(
+						`@removeListener(${this.var}, "${handler.name}", ${handlerName}, ${optString});`
+					);
+				} else {
 					block.builders.hydrate.addLine(
 						`@addListener(${this.var}, "${handler.name}", ${handlerName});`
 					);
@@ -669,6 +688,7 @@ export default class ElementWrapper extends Wrapper {
 						`@removeListener(${this.var}, "${handler.name}", ${handlerName});`
 					);
 				}
+			}
 		});
 	}
 

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

@@ -0,0 +1,91 @@
+/* generated by Svelte vX.Y.Z */
+import { addListener, append, assign, createElement, createText, detachNode, init, insert, noop, proto, removeListener } from "svelte/shared.js";
+
+var methods = {
+	handleTouchstart() {
+		// ...
+	},
+
+	handleClick() {
+		// ...
+	}
+};
+
+function create_main_fragment(component, ctx) {
+	var div, button0, text1, button1, text3, button2;
+
+	function click_handler(event) {
+		event.preventDefault();
+		event.stopPropagation();
+		component.handleClick();
+	}
+
+	function click_handler_1(event) {
+		component.handleClick();
+	}
+
+	function click_handler_2(event) {
+		component.handleClick();
+	}
+
+	function touchstart_handler(event) {
+		component.handleTouchstart();
+	}
+
+	return {
+		c() {
+			div = createElement("div");
+			button0 = createElement("button");
+			button0.textContent = "click me";
+			text1 = createText("\n\t");
+			button1 = createElement("button");
+			button1.textContent = "or me";
+			text3 = createText("\n\t");
+			button2 = createElement("button");
+			button2.textContent = "or me!";
+			addListener(button0, "click", click_handler);
+			addListener(button1, "click", click_handler_1, { once: true, capture: true });
+			addListener(button2, "click", click_handler_2, true);
+			addListener(div, "touchstart", touchstart_handler, { passive: true });
+		},
+
+		m(target, anchor) {
+			insert(target, div, anchor);
+			append(div, button0);
+			append(div, text1);
+			append(div, button1);
+			append(div, text3);
+			append(div, button2);
+		},
+
+		p: noop,
+
+		d(detach) {
+			if (detach) {
+				detachNode(div);
+			}
+
+			removeListener(button0, "click", click_handler);
+			removeListener(button1, "click", click_handler_1, { once: true, capture: true });
+			removeListener(button2, "click", click_handler_2, true);
+			removeListener(div, "touchstart", touchstart_handler, { passive: true });
+		}
+	};
+}
+
+function SvelteComponent(options) {
+	init(this, options);
+	this._state = assign({}, options.data);
+	this._intro = true;
+
+	this._fragment = create_main_fragment(this, this._state);
+
+	if (options.target) {
+		this._fragment.c();
+		this._mount(options.target, options.anchor);
+	}
+}
+
+assign(SvelteComponent.prototype, proto);
+assign(SvelteComponent.prototype, methods);
+export default SvelteComponent;

test/js/samples/event-modifiers/input.html

@@ -0,0 +1,19 @@
+<div on:touchstart="handleTouchstart()">
+	<button on:click|stopPropagation|preventDefault="handleClick()">click me</button>
+	<button on:click|once|capture="handleClick()">or me</button>
+	<button on:click|capture="handleClick()">or me!</button>
+</div>
+
+<script>
+	export default {
+		methods: {
+			handleTouchstart() {
+				// ...
+			},
+
+			handleClick() {
+				// ...
+			}
+		}
+	};
+</script>

test/parser/samples/event-handler/output.json

@@ -15,6 +15,7 @@
 						"end": 45,
 						"type": "EventHandler",
 						"name": "click",
+						"modifiers": [],
 						"expression": {
 							"type": "CallExpression",
 							"start": 18,