Await: re-throw error when there is no catch block and promise is rejected (#5149)

Author: irshadshalu

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

@@ -188,6 +188,7 @@ export default class AwaitBlockWrapper extends Wrapper {
 			ctx: #ctx,
 			current: null,
 			token: null,
+			hasCatch: ${this.catch.node.start !== null ? 'true' : 'false'},
 			pending: ${this.pending.block.name},
 			then: ${this.then.block.name},
 			catch: ${this.catch.block.name},

src/runtime/internal/await_block.ts

@@ -59,6 +59,9 @@ export function handle_promise(promise, info) {
 			update(info.then, 1, info.value, value);
 			set_current_component(null);
 		}, error => {
+			if (!info.hasCatch) {
+				throw error;
+			}
 			set_current_component(current_component);
 			update(info.catch, 2, info.error, error);
 			set_current_component(null);

test/runtime/samples/await-without-catch/_config.js

@@ -0,0 +1,44 @@
+let fulfil;
+
+let promise = new Promise(f => {
+	fulfil = f;
+});
+
+export default {
+	props: {
+		promise
+	},
+
+	html: `
+		<p>loading...</p>
+	`,
+
+	test({ assert, component, target }) {
+		fulfil(42);
+
+		return promise
+		.then(() => {
+			assert.htmlEqual(target.innerHTML, `
+				<p>loaded</p>
+			`);
+
+			let reject;
+
+			promise = new Promise((f, r) => {
+				reject = r;
+			});
+
+			component.promise = promise;
+
+			assert.htmlEqual(target.innerHTML, `
+				<p>loading...</p>
+			`);
+
+			reject(new Error('this error should be thrown'));
+			return promise;
+		})
+		.catch((err) => {
+			assert.equal(err.message, 'this error should be thrown');
+		});
+	}
+};

test/runtime/samples/await-without-catch/main.svelte

@@ -0,0 +1,9 @@
+<script>
+	export let promise;
+</script>
+
+{#await promise}
+	<p>loading...</p>
+{:then value}
+	<p>loaded</p>
+{/await}