Python: Fix event loop terminating too early when the main coro finishes

Author: tronical

api/python/slint/slint/__init__.py

@@ -465,9 +465,9 @@ async def run_inner() -> None:
         global quit_event
         loop = typing.cast(SlintEventLoop, asyncio.get_event_loop())
 
-        tasks: typing.List[asyncio.Task[typing.Any]] = [
-            asyncio.ensure_future(quit_event.wait(), loop=loop)
-        ]
+        quit_task = asyncio.ensure_future(quit_event.wait(), loop=loop)
+
+        tasks: typing.List[asyncio.Task[typing.Any]] = [quit_task]
 
         main_task = None
         if main_coro:
@@ -478,6 +478,8 @@ async def run_inner() -> None:
 
         if main_task is not None and main_task in done:
             main_task.result()  # propagate exception if thrown
+            if quit_task in pending:
+                await quit_event.wait()
 
     global quit_event
     quit_event = asyncio.Event()

api/python/slint/tests/test_async.py

@@ -12,6 +12,7 @@
 import pytest
 import sys
 import platform
+from datetime import timedelta
 
 
 def test_async_basic() -> None:
@@ -181,6 +182,23 @@ async def never_quit() -> None:
         pytest.fail("Should not throw a run-time error")
 
 
+def test_loop_continues_when_main_coro_finished() -> None:
+    async def quit_later(quit_event: asyncio.Event) -> None:
+        await quit_event.wait()
+        slint.quit_event_loop()
+
+    async def simple(quit_event: asyncio.Event) -> None:
+        loop = asyncio.get_event_loop()
+        loop.create_task(quit_later(quit_event))
+
+    quit_event = asyncio.Event()
+    slint.Timer.single_shot(
+        duration=timedelta(milliseconds=100), callback=lambda: quit_event.set()
+    )
+    slint.run_event_loop(simple(quit_event))
+    assert quit_event.is_set()
+
+
 @pytest.mark.skipif(platform.system() == "Windows", reason="pipes aren't supported yet")
 def test_subprocess() -> None:
     async def launch_process(exception_check: typing.List[Exception]) -> None: