From b22abcdbbedb0f7583b19031fd65e19b3883671d Mon Sep 17 00:00:00 2001
From: Jim Mussared <jim.mussared@gmail.com>
Date: Thu, 21 Jul 2022 09:54:02 +1000
Subject: [PATCH] extmod/uasyncio: Handle gather with no awaitables.

This previously resulted in gather() yielding but with no way to be
resumed.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
---
 extmod/uasyncio/funcs.py            | 3 +++
 tests/extmod/uasyncio_gather.py     | 5 +++++
 tests/extmod/uasyncio_gather.py.exp | 2 ++
 3 files changed, 10 insertions(+)

diff --git a/extmod/uasyncio/funcs.py b/extmod/uasyncio/funcs.py
index a1d38fbcbf..96883e4fe1 100644
--- a/extmod/uasyncio/funcs.py
+++ b/extmod/uasyncio/funcs.py
@@ -62,6 +62,9 @@ class _Remove:
 
 
 async def gather(*aws, return_exceptions=False):
+    if not aws:
+        return []
+
     def done(t, er):
         # Sub-task "t" has finished, with exception "er".
         nonlocal state
diff --git a/tests/extmod/uasyncio_gather.py b/tests/extmod/uasyncio_gather.py
index c081221c9f..af6ea555ab 100644
--- a/tests/extmod/uasyncio_gather.py
+++ b/tests/extmod/uasyncio_gather.py
@@ -53,6 +53,11 @@ async def main():
 
     print("====")
 
+    # Gather with no awaitables
+    print(await asyncio.gather())
+
+    print("====")
+
     # Test return_exceptions, where one task is cancelled and the other finishes normally
     tasks = [asyncio.create_task(task(1)), asyncio.create_task(task(2))]
     tasks[0].cancel()
diff --git a/tests/extmod/uasyncio_gather.py.exp b/tests/extmod/uasyncio_gather.py.exp
index a5ea47ab50..371d1ae60d 100644
--- a/tests/extmod/uasyncio_gather.py.exp
+++ b/tests/extmod/uasyncio_gather.py.exp
@@ -9,6 +9,8 @@ Task C: Compute factorial(4)...
 Task C: factorial(4) = 24
 [2, 6, 24]
 ====
+[]
+====
 start 2
 end 2
 [CancelledError(), 2]