Do not fail on mapping empty collections

asyncio_pool/base_pool.py

@@ -238,6 +238,9 @@ async def map(self, fn, iterable, cb=None, ctx=None, *,
             fut = await self.spawn(fn(it), cb, ctx)
             futures.append(fut)
 
+        if not futures:
+            return []
+
         await aio.wait(futures)
         return [get_result(fut) for fut in futures]
 

tests/test_map.py

@@ -16,6 +16,14 @@ async def test_map_simple():
     assert res == [i*10 for i in task]
 
 
+@pytest.mark.asyncio
+async def test_map_empty():
+    task = []
+    pool = AioPool(size=7)
+    res = await pool.map(wrk, task)
+    assert res == []
+
+
 @pytest.mark.asyncio
 async def test_map_crash():
     task = range(5)
@@ -52,6 +60,17 @@ async def wrk(n):
             i += 1  # does not support enumerate btw (
 
 
+@pytest.mark.asyncio
+async def test_itermap_empty():
+    async def wrk(n):
+        await aio.sleep(n)
+        return n
+
+    async with AioPool(size=3) as pool:
+        async for res in pool.itermap(wrk, [], flat=False, timeout=0.6):
+            assert False
+
+
 @pytest.mark.asyncio
 async def test_itermap_cancel():