extmod/uasyncio: Fix gather cancelling and handling of exceptions.

The following fixes are made:
- cancelling a gather now cancels all sub-tasks of the gather (previously
  it would only cancel the first)
- if any sub-task of a gather raises an exception then the gather finishes
  (previously it would only finish if the first sub-task raised)

Fixes issues #5798, #7807, #7901.

Signed-off-by: Damien George <damien@micropython.org>

1 files changed, 53 insertions, 10 deletions

diff --git a/tests/extmod/uasyncio_gather.py b/tests/extmod/uasyncio_gather.py
index 6053873dbc..718e702be6 100644
--- a/tests/extmod/uasyncio_gather.py
+++ b/tests/extmod/uasyncio_gather.py
@@ -27,9 +27,22 @@ async def task(id):
     return id
 
 
-async def gather_task():
+async def task_loop(id):
+    print("task_loop start", id)
+    while True:
+        await asyncio.sleep(0.02)
+        print("task_loop loop", id)
+
+
+async def task_raise(id):
+    print("task_raise start", id)
+    await asyncio.sleep(0.02)
+    raise ValueError(id)
+
+
+async def gather_task(t0, t1):
     print("gather_task")
-    await asyncio.gather(task(1), task(2))
+    await asyncio.gather(t0, t1)
     print("gather_task2")
 
 
@@ -37,19 +50,49 @@ async def main():
     # Simple gather with return values
     print(await asyncio.gather(factorial("A", 2), factorial("B", 3), factorial("C", 4)))
 
+    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()
     print(await asyncio.gather(*tasks, return_exceptions=True))
 
-    # Cancel a multi gather
-    # TODO doesn't work, Task should not forward cancellation from gather to sub-task
-    # but rather CancelledError should cancel the gather directly, which will then cancel
-    # all sub-tasks explicitly
-    # t = asyncio.create_task(gather_task())
-    # await asyncio.sleep(0.01)
-    # t.cancel()
-    # await asyncio.sleep(0.01)
+    print("====")
+
+    # Test return_exceptions, where one task raises an exception and the other finishes normally.
+    tasks = [asyncio.create_task(task(1)), asyncio.create_task(task_raise(2))]
+    print(await asyncio.gather(*tasks, return_exceptions=True))
+
+    print("====")
+
+    # Test case where one task raises an exception and other task keeps running.
+    tasks = [asyncio.create_task(task_loop(1)), asyncio.create_task(task_raise(2))]
+    try:
+        await asyncio.gather(*tasks)
+    except ValueError as er:
+        print(repr(er))
+    print(tasks[0].done(), tasks[1].done())
+    for t in tasks:
+        t.cancel()
+    await asyncio.sleep(0.04)
+
+    print("====")
+
+    # Test case where both tasks raise an exception.
+    tasks = [asyncio.create_task(task_raise(1)), asyncio.create_task(task_raise(2))]
+    try:
+        await asyncio.gather(*tasks)
+    except ValueError as er:
+        print(repr(er))
+    print(tasks[0].done(), tasks[1].done())
+
+    print("====")
+
+    # Cancel a multi gather.
+    t = asyncio.create_task(gather_task(task(1), task(2)))
+    await asyncio.sleep(0.01)
+    t.cancel()
+    await asyncio.sleep(0.04)
 
 
 asyncio.run(main())