From 8143f26af80f54394dd2bde92e35a4d7e1e4eabd Mon Sep 17 00:00:00 2001
From: Vladimir Kotikov <kotikov.vladimir@gmail.com>
Date: Mon, 28 Aug 2023 09:32:35 +0300
Subject: [PATCH] Do not fail on mapping empty collections

This is quite natural for map function to be a no-op and return an empty collection when input is also empty (the examples are the python's own map funvtion and nodejs' array.map function) rather than throwing an error which it does at the moment.
---
 asyncio_pool/base_pool.py |  3 +++
 tests/test_map.py         | 19 +++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/asyncio_pool/base_pool.py b/asyncio_pool/base_pool.py
index c96bcff..7056f21 100644
--- a/asyncio_pool/base_pool.py
+++ b/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]
 
diff --git a/tests/test_map.py b/tests/test_map.py
index 061f3ff..113fb37 100644
--- a/tests/test_map.py
+++ b/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():