fix: MuxAsyncIterator throws muxed errors (#6295)

Fixes #5260

1 files changed, 26 insertions, 1 deletions

diff --git a/std/async/mux_async_iterator_test.ts b/std/async/mux_async_iterator_test.ts
index 7017a4eba..5ca28903b 100644
--- a/std/async/mux_async_iterator_test.ts
+++ b/std/async/mux_async_iterator_test.ts
@@ -1,5 +1,5 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { assertEquals } from "../testing/asserts.ts";
+import { assertEquals, assertThrowsAsync } from "../testing/asserts.ts";
 import { MuxAsyncIterator } from "./mux_async_iterator.ts";
 
 // eslint-disable-next-line require-await
@@ -16,6 +16,12 @@ async function* gen456(): AsyncIterableIterator<number> {
   yield 6;
 }
 
+// eslint-disable-next-line require-await
+async function* genThrows(): AsyncIterableIterator<number> {
+  yield 7;
+  throw new Error("something went wrong");
+}
+
 Deno.test("[async] MuxAsyncIterator", async function (): Promise<void> {
   const mux = new MuxAsyncIterator<number>();
   mux.add(gen123());
@@ -26,3 +32,22 @@ Deno.test("[async] MuxAsyncIterator", async function (): Promise<void> {
   }
   assertEquals(results.size, 6);
 });
+
+Deno.test({
+  name: "[async] MuxAsyncIterator throws",
+  async fn() {
+    const mux = new MuxAsyncIterator<number>();
+    mux.add(gen123());
+    mux.add(genThrows());
+    const results = new Set();
+    await assertThrowsAsync(
+      async () => {
+        for await (const value of mux) {
+          results.add(value);
+        }
+      },
+      Error,
+      "something went wrong"
+    );
+  },
+});