Fix #21

Author: nicolas-van

src/asyncGeneratorMap.mjs

@@ -183,7 +183,17 @@ async function * asyncGeneratorMap (iterable, iteratee, queueOrConcurrency = 1,
       if (result.snapshot.status === 'rejected') {
         throw result.snapshot.reason
       } else {
-        yield result.snapshot.value
+        let yielded = false
+        try {
+          yield result.snapshot.value
+          yielded = true
+        } finally {
+          if (!yielded)
+          {
+            await it.return()
+            return
+          }
+        }
       }
     }
     if (exhausted && lastIndexFetched === lastIndexHandled) {

src/asyncGeneratorMap.test.mjs

@@ -632,3 +632,75 @@ test('asyncGeneratorMap reaches concurrency', async () => {
   expect(maxConcurrency).toStrictEqual(expectedConcurrency)
   expect(result).toStrictEqual(await asyncIterableToArray(range(100)))
 })
+
+test('common for await interrupts generator on interrupted iteration', async () => {
+
+  let finallyReached = false;
+
+  async function *asyncGenWithFinally() {
+    try {
+      for (const element of range(10)) {
+        yield element;
+      }
+    } finally {
+      finallyReached = true;
+    }
+  }
+
+  for await (const n of asyncGenWithFinally()) {
+    if (n === 2) {
+      break
+    }
+  }
+
+  expect(finallyReached).toBe(true);
+})
+
+test('common for await calls AsyncGenerator.return() not AsyncGenerator.throw()', async () => {
+
+  let catchedException = null;
+
+  async function *asyncGenWithFinally() {
+    try {
+      for (const element of range(10)) {
+        yield element;
+      }
+    } catch (e) {
+      catchedException = e;
+    }
+  }
+
+  try {
+    for await (const n of asyncGenWithFinally()) {
+      if (n === 2) {
+        throw new TestError();
+      }
+    }
+  } catch (e) // ignore
+  {
+    expect(e instanceof TestError).toBe(true)
+  }
+  expect(catchedException).toBe(null);
+})
+
+test('asyncGeneratorMap interrupts generator on interrupted iteration', async () => {
+
+  let finallyReached = false;
+
+  async function *asyncGenWithFinally() {
+    try {
+      for (const element of range(10)) {
+        yield element;
+      }
+    } finally {
+      finallyReached = true;
+    }
+  }
+
+  for await (const n of asyncGeneratorMap(asyncGenWithFinally(), n => n*2)) {
+    if (n === 4) {
+      break
+    }
+  }
+  expect(finallyReached).toBe(true);
+})