dispatch transition events inside render callback - fixes #2158

src/internal/transitions.js

@@ -2,6 +2,7 @@ import { identity as linear, noop, run_all } from './utils.js';
 import { loop } from './loop.js';
 import { create_rule, delete_rule } from './style_manager.js';
 import { custom_event } from './dom.js';
+import { add_render_callback } from './scheduler.js';
 
 let promise;
 
@@ -16,6 +17,10 @@ function wait() {
 	return promise;
 }
 
+function dispatch(node, direction, kind) {
+	node.dispatchEvent(custom_event(`${direction ? 'intro' : 'outro'}${kind}`));
+}
+
 let outros;
 
 export function group_outros() {
@@ -239,14 +244,14 @@ export function create_bidirectional_transition(node, fn, params, intro) {
 			if (b) tick(0, 1);
 
 			running_program = init(program, duration);
-			node.dispatchEvent(custom_event(`${running_program.b ? 'intro' : 'outro'}start`));
+			add_render_callback(() => dispatch(node, b, 'start'))
 
 			loop(now => {
 				if (pending_program && now > pending_program.start) {
 					running_program = init(pending_program, duration);
 					pending_program = null;
 
-					node.dispatchEvent(custom_event(`${running_program.b ? 'intro' : 'outro'}start`));
+					dispatch(node, running_program.b, 'start');
 
 					if (css) {
 						clear_animation();
@@ -257,7 +262,7 @@ export function create_bidirectional_transition(node, fn, params, intro) {
 				if (running_program) {
 					if (now >= running_program.end) {
 						tick(t = running_program.b, 1 - t);
-						node.dispatchEvent(custom_event(`${running_program.b ? 'intro' : 'outro'}end`));
+						dispatch(node, running_program.b, 'end');
 
 						if (!pending_program) {
 							// we're done

test/runtime/samples/transition-js-events/_config.js

@@ -1,21 +1,51 @@
 export default {
 	props: {
-		visible: true,
+		visible: false,
 		things: ['a', 'b', 'c', 'd']
 	},
 
-	intro: true,
+	// intro: true,
+
+	html: `
+		<p>waiting...</p>
+	`,
+
+	async test({ assert, component, target, raf }) {
+		component.visible = true;
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>introstart</p>
+			<p>a</p>
+			<p>b</p>
+			<p>c</p>
+			<p>d</p>
+		`);
 
-	test({ assert, component, target, window, raf }) {
 		raf.tick(50);
 		assert.deepEqual(component.intros.sort(), ['a', 'b', 'c', 'd']);
 		assert.equal(component.intro_count, 4);
 
-		raf.tick(100);
+		await raf.tick(100);
 		assert.equal(component.intro_count, 0);
 
+		assert.htmlEqual(target.innerHTML, `
+			<p>introend</p>
+			<p>a</p>
+			<p>b</p>
+			<p>c</p>
+			<p>d</p>
+		`);
+
 		component.visible = false;
 
+		assert.htmlEqual(target.innerHTML, `
+			<p>outrostart</p>
+			<p>a</p>
+			<p>b</p>
+			<p>c</p>
+			<p>d</p>
+		`);
+
 		raf.tick(150);
 		assert.deepEqual(component.outros.sort(), ['a', 'b', 'c', 'd']);
 		assert.equal(component.outro_count, 4);
@@ -24,12 +54,17 @@ export default {
 		assert.equal(component.outro_count, 0);
 
 		component.visible = true;
-		component.$on('intro.start', () => {
-			throw new Error(`intro.start should fire during set(), not after`);
-		});
 
-		raf.tick(250);
+		await raf.tick(250);
 		assert.deepEqual(component.intros.sort(), ['a', 'a', 'b', 'b', 'c', 'c', 'd', 'd']);
 		assert.equal(component.intro_count, 4);
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>introstart</p>
+			<p>a</p>
+			<p>b</p>
+			<p>c</p>
+			<p>d</p>
+		`);
 	}
 };

test/runtime/samples/transition-js-events/main.svelte

@@ -9,6 +9,8 @@
 	export let intro_count = 0;
 	export let outro_count = 0;
 
+	let status = 'waiting...';
+
 	function foo(node, params) {
 		return {
 			duration: 100,
@@ -21,22 +23,28 @@
 	function introstart(e) {
 		intros.push(e.target.textContent);
 		intro_count += 1;
+		status = 'introstart';
 	}
 
 	function introend(e) {
 		intro_count -= 1;
+		status = 'introend';
 	}
 
 	function outrostart(e) {
 		outros.push(e.target.textContent);
 		outro_count += 1;
+		status = 'outrostart';
 	}
 
 	function outroend(e) {
 		outro_count -= 1;
+		status = 'outroend';
 	}
 </script>
 
+<p>{status}</p>
+
 {#each things as thing}
 	{#if visible}
 		<p