Allow multiple event listeners on a single node

src/parse/state/tag.ts

@@ -131,8 +131,8 @@ export default function tag(parser: Parser) {
 	const type = meta_tags.has(name)
 		? meta_tags.get(name)
 		: (/[A-Z]/.test(name[0]) || name === 'svelte:self' || name === 'svelte:component') ? 'InlineComponent'
-		: name === 'title' && parent_is_head(parser.stack) ? 'Title'
-		: name === 'slot' && !parser.customElement ? 'Slot' : 'Element';
+			: name === 'title' && parent_is_head(parser.stack) ? 'Title'
+				: name === 'slot' && !parser.customElement ? 'Slot' : 'Element';
 
 	const element: Node = {
 		start,
@@ -360,14 +360,6 @@ function read_attribute(parser: Parser, unique_names: Set<string>) {
 
 	let name = parser.read_until(/(\s|=|\/|>)/);
 	if (!name) return null;
-	if (unique_names.has(name)) {
-		parser.error({
-			code: `duplicate-attribute`,
-			message: 'Attributes need to be unique'
-		}, start);
-	}
-
-	unique_names.add(name);
 
 	let end = parser.index;
 
@@ -376,6 +368,15 @@ function read_attribute(parser: Parser, unique_names: Set<string>) {
 	const colon_index = name.indexOf(':');
 	const type = colon_index !== -1 && get_directive_type(name.slice(0, colon_index));
 
+	if (unique_names.has(name) && type != "EventHandler") {
+		parser.error({
+			code: `duplicate-attribute`,
+			message: 'Attributes need to be unique'
+		}, start);
+	}
+
+	unique_names.add(name);
+
 	let value: any[] | true = true;
 	if (parser.eat('=')) {
 		value = read_attribute_value(parser);
@@ -453,8 +454,8 @@ function read_attribute_value(parser: Parser) {
 
 	const regex = (
 		quote_mark === `'` ? /'/ :
-		quote_mark === `"` ? /"/ :
-		/(\/>|[\s"'=<>`])/
+			quote_mark === `"` ? /"/ :
+				/(\/>|[\s"'=<>`])/
 	);
 
 	const value = read_sequence(parser, () => !!parser.match_regex(regex));

test/parser/samples/non-unique-attribute-event-handler/input.svelte

@@ -0,0 +1 @@
+<button on:click="{() => visible = !visible}" on:click="{() => ajax = false}"></button>

test/parser/samples/non-unique-attribute-event-handler/output.json

@@ -0,0 +1,96 @@
+{
+	"html": {
+		"start": 0,
+		"end": 87,
+		"type": "Fragment",
+		"children": [
+			{
+				"start": 0,
+				"end": 87,
+				"type": "Element",
+				"name": "button",
+				"attributes": [
+					{
+						"start": 8,
+						"end": 45,
+						"type": "EventHandler",
+						"name": "click",
+						"modifiers": [],
+						"expression": {
+							"type": "ArrowFunctionExpression",
+							"start": 19,
+							"end": 43,
+							"id": null,
+							"expression": true,
+							"generator": false,
+							"async": false,
+							"params": [],
+							"body": {
+								"type": "AssignmentExpression",
+								"start": 25,
+								"end": 43,
+								"operator": "=",
+								"left": {
+									"type": "Identifier",
+									"start": 25,
+									"end": 32,
+									"name": "visible"
+								},
+								"right": {
+									"type": "UnaryExpression",
+									"start": 35,
+									"end": 43,
+									"operator": "!",
+									"prefix": true,
+									"argument": {
+										"type": "Identifier",
+										"start": 36,
+										"end": 43,
+										"name": "visible"
+									}
+								}
+							}
+						}
+					},
+					{
+						"start": 46,
+						"end": 77,
+						"type": "EventHandler",
+						"name": "click",
+						"modifiers": [],
+						"expression": {
+							"type": "ArrowFunctionExpression",
+							"start": 57,
+							"end": 75,
+							"id": null,
+							"expression": true,
+							"generator": false,
+							"async": false,
+							"params": [],
+							"body": {
+								"type": "AssignmentExpression",
+								"start": 63,
+								"end": 75,
+								"operator": "=",
+								"left": {
+									"type": "Identifier",
+									"start": 63,
+									"end": 67,
+									"name": "ajax"
+								},
+								"right": {
+									"type": "Literal",
+									"start": 70,
+									"end": 75,
+									"value": false,
+									"raw": "false"
+								}
+							}
+						}
+					}
+				],
+				"children": []
+			}
+		]
+	}
+}