prevent await block mounting inside removed if block - fixes #1496

Author: Rich-Harris

src/compiler/compile/render_dom/wrappers/AwaitBlock.ts

@@ -137,6 +137,7 @@ export default class AwaitBlockWrapper extends Wrapper {
 		const info_props = [
 			'ctx',
 			'current: null',
+			'token: null',
 			this.pending.block.name && `pending: ${this.pending.block.name}`,
 			this.then.block.name && `then: ${this.then.block.name}`,
 			this.catch.block.name && `catch: ${this.catch.block.name}`,
@@ -223,6 +224,7 @@ export default class AwaitBlockWrapper extends Wrapper {
 
 		block.builders.destroy.add_block(deindent`
 			${info}.block.d(${parent_node ? '' : 'detaching'});
+			${info}.token = null;
 			${info} = null;
 		`);
 

test/runtime/index.js

@@ -21,6 +21,11 @@ let compile = null;
 
 const sveltePath = process.cwd().split('\\').join('/');
 
+let unhandled_rejection = false;
+process.on('unhandledRejection', err => {
+	unhandled_rejection = err;
+});
+
 describe("runtime", () => {
 	before(() => {
 		svelte = loadSvelte(false);
@@ -60,6 +65,8 @@ describe("runtime", () => {
 				throw new Error('skipping test, already failed');
 			}
 
+			unhandled_rejection = null;
+
 			compile = (config.preserveIdentifiers ? svelte : svelte$).compile;
 
 			const cwd = path.resolve(`test/runtime/samples/${dir}`);
@@ -165,10 +172,18 @@ describe("runtime", () => {
 							raf
 						})).then(() => {
 							component.$destroy();
+
+							if (unhandled_rejection) {
+								throw unhandled_rejection;
+							}
 						});
 					} else {
 						component.$destroy();
 						assert.htmlEqual(target.innerHTML, "");
+
+						if (unhandled_rejection) {
+							throw unhandled_rejection;
+						}
 					}
 				})
 				.catch(err => {

test/runtime/samples/await-in-removed-if/_config.js

@@ -0,0 +1,22 @@
+let fulfil;
+
+const promise = new Promise(f => {
+	fulfil = f;
+});
+
+export default {
+	props: {
+		promise
+	},
+
+	html: ``,
+
+	async test({ assert, component, target }) {
+		component.condition = false;
+
+		fulfil();
+		await new Promise(f => setTimeout(f, 0));
+
+		assert.htmlEqual(target.innerHTML, ``);
+	}
+};

test/runtime/samples/await-in-removed-if/main.svelte

@@ -0,0 +1,8 @@
+<script>
+	export let promise;
+	export let condition = true;
+</script>
+
+{#if condition}
+	{#await promise then _}hello{/await}
+{/if}