gh-110771: Decompose run_forever() into parts (#110773)

Effectively introduce an unstable, private (really: protected) API for subclasses that want to override `run_forever()`.

1 files changed, 19 insertions, 18 deletions

diff --git a/Lib/asyncio/windows_events.py b/Lib/asyncio/windows_events.py
index 4a4c4be..b62ea75 100644
--- a/Lib/asyncio/windows_events.py
+++ b/Lib/asyncio/windows_events.py
@@ -314,24 +314,25 @@ class ProactorEventLoop(proactor_events.BaseProactorEventLoop):
             proactor = IocpProactor()
         super().__init__(proactor)
 
-    def run_forever(self):
-        try:
-            assert self._self_reading_future is None
-            self.call_soon(self._loop_self_reading)
-            super().run_forever()
-        finally:
-            if self._self_reading_future is not None:
-                ov = self._self_reading_future._ov
-                self._self_reading_future.cancel()
-                # self_reading_future was just cancelled so if it hasn't been
-                # finished yet, it never will be (it's possible that it has
-                # already finished and its callback is waiting in the queue,
-                # where it could still happen if the event loop is restarted).
-                # Unregister it otherwise IocpProactor.close will wait for it
-                # forever
-                if ov is not None:
-                    self._proactor._unregister(ov)
-                self._self_reading_future = None
+    def _run_forever_setup(self):
+        assert self._self_reading_future is None
+        self.call_soon(self._loop_self_reading)
+        super()._run_forever_setup()
+
+    def _run_forever_cleanup(self):
+        super()._run_forever_cleanup()
+        if self._self_reading_future is not None:
+            ov = self._self_reading_future._ov
+            self._self_reading_future.cancel()
+            # self_reading_future was just cancelled so if it hasn't been
+            # finished yet, it never will be (it's possible that it has
+            # already finished and its callback is waiting in the queue,
+            # where it could still happen if the event loop is restarted).
+            # Unregister it otherwise IocpProactor.close will wait for it
+            # forever
+            if ov is not None:
+                self._proactor._unregister(ov)
+            self._self_reading_future = None
 
     async def create_pipe_connection(self, protocol_factory, address):
         f = self._proactor.connect_pipe(address)