bpo-33792: Add selector and proactor windows policies (GH-7487)

(cherry picked from commit 8f40429)

Co-authored-by: Yury Selivanov <yury@magic.io>

Author: miss-islington

Doc/whatsnew/3.7.rst

@@ -733,6 +733,10 @@ include:
 * Exceptions occurring in cancelled tasks are no longer logged.
   (Contributed by Yury Selivanov in :issue:`30508`.)
 
+* New ``WindowsSelectorEventLoopPolicy`` and
+  ``WindowsProactorEventLoopPolicy`` classes.
+  (Contributed by Yury Selivanov in :issue:`33792`.)
+
 Several ``asyncio`` APIs have been
 :ref:`deprecated <whatsnew37-asyncio-deprecated>`.
 

Lib/asyncio/windows_events.py

@@ -21,7 +21,8 @@
 
 __all__ = (
     'SelectorEventLoop', 'ProactorEventLoop', 'IocpProactor',
-    'DefaultEventLoopPolicy',
+    'DefaultEventLoopPolicy', 'WindowsSelectorEventLoopPolicy',
+    'WindowsProactorEventLoopPolicy',
 )
 
 
@@ -801,8 +802,12 @@ def callback(f):
 SelectorEventLoop = _WindowsSelectorEventLoop
 
 
-class _WindowsDefaultEventLoopPolicy(events.BaseDefaultEventLoopPolicy):
+class WindowsSelectorEventLoopPolicy(events.BaseDefaultEventLoopPolicy):
     _loop_factory = SelectorEventLoop
 
 
-DefaultEventLoopPolicy = _WindowsDefaultEventLoopPolicy
+class WindowsProactorEventLoopPolicy(events.BaseDefaultEventLoopPolicy):
+    _loop_factory = ProactorEventLoop
+
+
+DefaultEventLoopPolicy = WindowsSelectorEventLoopPolicy

Lib/test/test_asyncio/test_windows_events.py

@@ -162,5 +162,36 @@ def test_wait_for_handle_cancel(self):
         fut.cancel()
 
 
+class WinPolicyTests(test_utils.TestCase):
+
+    def test_selector_win_policy(self):
+        async def main():
+            self.assertIsInstance(
+                asyncio.get_running_loop(),
+                asyncio.SelectorEventLoop)
+
+        old_policy = asyncio.get_event_loop_policy()
+        try:
+            asyncio.set_event_loop_policy(
+                asyncio.WindowsSelectorEventLoopPolicy())
+            asyncio.run(main())
+        finally:
+            asyncio.set_event_loop_policy(old_policy)
+
+    def test_proactor_win_policy(self):
+        async def main():
+            self.assertIsInstance(
+                asyncio.get_running_loop(),
+                asyncio.ProactorEventLoop)
+
+        old_policy = asyncio.get_event_loop_policy()
+        try:
+            asyncio.set_event_loop_policy(
+                asyncio.WindowsProactorEventLoopPolicy())
+            asyncio.run(main())
+        finally:
+            asyncio.set_event_loop_policy(old_policy)
+
+
 if __name__ == '__main__':
     unittest.main()

Misc/NEWS.d/next/Library/2018-06-07-12-38-12.bpo-33792.3aKG7u.rst

@@ -0,0 +1,2 @@
+Add asyncio.WindowsSelectorEventLoopPolicy and
+asyncio.WindowsProactorEventLoopPolicy.