From c221924aece0f0bc434c0b0dc787a2fcd04a3943 Mon Sep 17 00:00:00 2001
From: scarf <greenscarf005@gmail.com>
Date: Tue, 8 Oct 2024 23:20:01 +0900
Subject: [PATCH] feat(async/unstable): accept iterator varargs in
 `MuxAsyncIterator` (#6087)

Co-authored-by: Yoshiya Hinosawa <stibium121@gmail.com>
---
 async/deno.json                           |  1 +
 async/unstable_mux_async_iterator.ts      | 50 +++++++++++++++++++++++
 async/unstable_mux_async_iterator_test.ts | 22 ++++++++++
 3 files changed, 73 insertions(+)
 create mode 100644 async/unstable_mux_async_iterator.ts
 create mode 100644 async/unstable_mux_async_iterator_test.ts

diff --git a/async/deno.json b/async/deno.json
index c2c5e4ad8..b3cdcd23c 100644
--- a/async/deno.json
+++ b/async/deno.json
@@ -8,6 +8,7 @@
     "./debounce": "./debounce.ts",
     "./delay": "./delay.ts",
     "./mux-async-iterator": "./mux_async_iterator.ts",
+    "./unstable-mux-async-iterator": "./unstable_mux_async_iterator.ts",
     "./pool": "./pool.ts",
     "./retry": "./retry.ts",
     "./tee": "./tee.ts"
diff --git a/async/unstable_mux_async_iterator.ts b/async/unstable_mux_async_iterator.ts
new file mode 100644
index 000000000..3cc157ce7
--- /dev/null
+++ b/async/unstable_mux_async_iterator.ts
@@ -0,0 +1,50 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+// This module is browser compatible.
+
+import { MuxAsyncIterator as MaxAsyncIterator_ } from "./mux_async_iterator.ts";
+
+/**
+ * Multiplexes multiple async iterators into a single stream. It currently
+ * makes an assumption that the final result (the value returned and not
+ * yielded from the iterator) does not matter; if there is any result, it is
+ * discarded.
+ *
+ * @experimental **UNSTABLE**: New API, yet to be vetted.
+ *
+ * @example Usage
+ * ```ts
+ * import { MuxAsyncIterator } from "@std/async/unstable-mux-async-iterator";
+ * import { assertEquals } from "@std/assert";
+ *
+ * async function* gen123(): AsyncIterableIterator<number> {
+ *   yield 1;
+ *   yield 2;
+ *   yield 3;
+ * }
+ *
+ * async function* gen456(): AsyncIterableIterator<number> {
+ *   yield 4;
+ *   yield 5;
+ *   yield 6;
+ * }
+ *
+ * const mux = new MuxAsyncIterator(gen123(), gen456());
+ *
+ * const result = await Array.fromAsync(mux);
+ *
+ * assertEquals(result, [1, 4, 2, 5, 3, 6]);
+ * ```
+ *
+ * @typeParam T The type of the provided async iterables and generated async iterable.
+ */
+export class MuxAsyncIterator<T> extends MaxAsyncIterator_<T> {
+  /**
+   * Constructs a new {@linkcode MuxAsyncIterator} instance.
+   *
+   * @param iterables The async iterables to multiplex.
+   */
+  constructor(...iterables: AsyncIterable<T>[]) {
+    super();
+    for (const iterable of iterables) this.add(iterable);
+  }
+}
diff --git a/async/unstable_mux_async_iterator_test.ts b/async/unstable_mux_async_iterator_test.ts
new file mode 100644
index 000000000..ada1cbae3
--- /dev/null
+++ b/async/unstable_mux_async_iterator_test.ts
@@ -0,0 +1,22 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+import { assertEquals } from "@std/assert";
+import { MuxAsyncIterator } from "./unstable_mux_async_iterator.ts";
+
+async function* gen123(): AsyncIterableIterator<number> {
+  yield 1;
+  yield 2;
+  yield 3;
+}
+
+async function* gen456(): AsyncIterableIterator<number> {
+  yield 4;
+  yield 5;
+  yield 6;
+}
+
+Deno.test("(unstable) MuxAsyncIterator() works with constructor iterables", async () => {
+  const mux = new MuxAsyncIterator(gen123(), gen456());
+  const results = new Set(await Array.fromAsync(mux));
+  assertEquals(results.size, 6);
+  assertEquals(results, new Set([1, 4, 2, 5, 3, 6]));
+});