fix(async): abortableAsyncIterable() should call .return() on the generator once aborted

async/abortable.ts

@@ -144,16 +144,21 @@ async function* abortableAsyncIterable<T>(
   signal.addEventListener("abort", abort, { once: true });
 
   const it = p[Symbol.asyncIterator]();
-  while (true) {
-    const race = Promise.race([promise, it.next()]);
-    race.catch(() => {
-      signal.removeEventListener("abort", abort);
-    });
-    const { done, value } = await race;
-    if (done) {
-      signal.removeEventListener("abort", abort);
-      return;
+  try {
+    while (true) {
+      const race = Promise.race([promise, it.next()]);
+      race.catch(() => {
+        signal.removeEventListener("abort", abort);
+      });
+      const { done, value } = await race;
+      if (done) {
+        signal.removeEventListener("abort", abort);
+        return;
+      }
+      yield value;
     }
-    yield value;
+  } catch (e) {
+    await it.return?.();
+    throw e;
   }
 }

async/abortable_test.ts

@@ -130,3 +130,34 @@ Deno.test("abortable.AsyncIterable() handles already aborted signal", async () =
   assertEquals(items, []);
   clearTimeout(t);
 });
+
+Deno.test("abortable.AsyncIterable() calls return before throwing", async () => {
+  const c = new AbortController();
+  let returnCalled = false;
+  const iterable: AsyncIterable<string> = {
+    [Symbol.asyncIterator]: () => ({
+      next: () =>
+        new Promise((resolve) =>
+          setTimeout(() => resolve({ value: "Hello", done: false }), 1)
+        ),
+      return: () => {
+        returnCalled = true;
+        return Promise.resolve({ value: undefined, done: true });
+      },
+    }),
+  };
+  setTimeout(() => c.abort(), 1);
+  const items: string[] = [];
+  const error = await assertRejects(
+    async () => {
+      for await (const item of abortable(iterable, c.signal)) {
+        items.push(item);
+      }
+    },
+    DOMException,
+    "The signal has been aborted",
+  );
+  assertEquals(returnCalled, true);
+  assertEquals(error.name, "AbortError");
+  assertEquals(items, []);
+});