include destroy as valid built-in method for event handlers (fixes #523)

src/validate/html/validateElement.js

@@ -1,5 +1,11 @@
 import flattenReference from '../../utils/flattenReference.js';
 
+const validBuiltins = new Set([
+	'set',
+	'fire',
+	'destroy'
+]);
+
 export default function validateElement ( validator, node ) {
 	const isComponent = node.name === ':Self' || validator.components.has( node.name );
 
@@ -56,10 +62,15 @@ export default function validateElement ( validator, node ) {
 			const { name } = flattenReference( callee );
 
 			if ( name === 'this' || name === 'event' ) return;
-			if ( callee.type === 'Identifier' && callee.name === 'set' || callee.name === 'fire' || validator.methods.has( callee.name ) ) return;
+			if ( callee.type === 'Identifier' && validBuiltins.has( callee.name ) || validator.methods.has( callee.name ) ) return;
+
+			const validCallees = [ 'this.*', 'event.*' ]
+				.concat(
+					Array.from( validBuiltins ),
+					Array.from( validator.methods.keys() )
+				);
 
-			const validCallees = list( [ 'this.*', 'event.*', 'set', 'fire' ].concat( Array.from( validator.methods.keys() ) ) );
-			let message = `'${validator.source.slice( callee.start, callee.end )}' is an invalid callee (should be one of ${validCallees})`;
+			let message = `'${validator.source.slice( callee.start, callee.end )}' is an invalid callee (should be one of ${list( validCallees )})`;
 
 			if ( callee.type === 'Identifier' && validator.helpers.has( callee.name ) ) {
 				message += `. '${callee.name}' exists on 'helpers', did you put it in the wrong place?`;

test/runtime/samples/event-handler-destroy/_config.js

@@ -0,0 +1,20 @@
+export default {
+	html: `
+		<button>destroy</button>
+	`,
+
+	test ( assert, component, target, window ) {
+		const button = target.querySelector( 'button' );
+		const event = new window.MouseEvent( 'click' );
+
+		let destroyed = false;
+		component.on( 'destroy', () => {
+			destroyed = true;
+		});
+
+		button.dispatchEvent( event );
+		assert.htmlEqual( target.innerHTML, `` );
+
+		assert.ok( destroyed );
+	}
+};

test/runtime/samples/event-handler-destroy/main.html

@@ -0,0 +1 @@
+<button on:click='destroy()'>destroy</button>

test/validator/samples/method-nonexistent-helper/errors.json

@@ -1,5 +1,5 @@
 [{
-	"message": "'foo' is an invalid callee (should be one of this.*, event.*, set, fire or bar). 'foo' exists on 'helpers', did you put it in the wrong place?",
+	"message": "'foo' is an invalid callee (should be one of this.*, event.*, set, fire, destroy or bar). 'foo' exists on 'helpers', did you put it in the wrong place?",
 	"pos": 18,
 	"loc": {
 		"line": 1,

test/validator/samples/method-nonexistent/errors.json

@@ -1,5 +1,5 @@
 [{
-	"message": "'foo' is an invalid callee (should be one of this.*, event.*, set, fire or bar)",
+	"message": "'foo' is an invalid callee (should be one of this.*, event.*, set, fire, destroy or bar)",
 	"pos": 18,
 	"loc": {
 		"line": 1,