TaskTask use saved coro_repr for __repr__ and ignore some Tasks

Summary:
Tasks that are done() and have a result of None, should be considered managed.  thrift-py3 does this in servers when it calls rpc methods, we don't have a way for the thrift server to monitor the python task since its results are stored in a C++ Folly Promise object.

Also the coro object can be garbage collected before the end of the test which makes understanding left over task errors very hard. So use the coro_repr we save in the `__init__` to make `__repr__` more useful.

Reviewed By: cooperlees

Differential Revision: D24550663

fbshipit-source-id: a8a4e20f1fbc670b75d4f1c4dc9c4f289c3a9123

later/__init__.py

@@ -18,7 +18,7 @@
 from .task import START_TASK, Watcher, WatcherError, as_task, cancel
 
 
-__version__ = "20.2.1"
+__version__ = "20.10.1"
 __all__ = [
     "BiDirectionalEvent",
     "START_TASK",

later/tests/unittest/test_case.py

@@ -37,6 +37,28 @@ async def test_managed_task_done(self):
         )
         await saved_done_task
 
+    async def test_managed_task_done_none(self):
+        global saved_done_task
+
+        async def coro(e: asyncio.Event) -> None:
+            e.set()
+
+        event = asyncio.Event()
+        saved_done_task = asyncio.get_running_loop().create_task(coro(event))
+        await event.wait()
+
+    @unittest.expectedFailure
+    async def test_unmanaged_task_done_value(self):
+        global saved_done_task
+
+        async def coro(e: asyncio.Event) -> bool:
+            e.set()
+            return False
+
+        event = asyncio.Event()
+        saved_done_task = asyncio.get_running_loop().create_task(coro(event))
+        await event.wait()
+
     @unittest.expectedFailure
     async def test_garbage_collected_task_during_testmethod(self):
         t = asyncio.get_running_loop().create_task(asyncio.sleep(10))

later/unittest/case.py

@@ -23,6 +23,7 @@
 import asyncio.futures
 import asyncio.log
 import asyncio.tasks
+import sys
 import unittest.mock as mock
 from functools import wraps
 from typing import Any, Callable, TypeVar
@@ -33,6 +34,7 @@
 _F = TypeVar("_F", bound=Callable[..., Any])
 _IGNORE_TASK_LEAKS_ATTR = "__later_testcase_ignore_tasks__"
 _IGNORE_AIO_ERRS_ATTR = "__later_testcase_ignore_asyncio__"
+atleastpy38 = sys.version_info[:2] >= (3, 8)
 
 
 class TestTask(asyncio.Task):
@@ -43,6 +45,15 @@ def __init__(self, coro, *args, **kws):
         self._coro_repr = asyncio.coroutines._format_coroutine(coro)
         super().__init__(coro, *args, **kws)
 
+    def __repr__(self):
+        repr_info = self._repr_info()
+        coro = f"coro={self._coro_repr}"
+        if atleastpy38:  # py3.8 added name=
+            repr_info[2] = coro  # pragma: nocover
+        else:
+            repr_info[1] = coro  # pragma: nocover
+        return f"<{self.__class__.__name__} {' '.join(repr_info)}>"
+
     def __await__(self):
         self._managed = True
         return super().__await__()
@@ -66,7 +77,15 @@ def mark_managed(fut):
         super().add_done_callback(mark_managed, context=context)
 
     def was_managed(self):
-        return self._managed
+        if self._managed:
+            return True
+        # If the task is done() and the result is None, let it pass as managed
+        return (
+            self.done()
+            and not self.cancelled()
+            and not self.exception()
+            and self.result() is None
+        )
 
     def __del__(self):
         # So a pattern is to create_task, and not save the results.
@@ -148,6 +167,7 @@ def _callTestMethod(self, testMethod):
         if not ignore_tasks:
             # install our own task factory for monitoring usage
             loop.set_task_factory(task_factory)
+
         # Track existing tasks
         start_tasks = all_tasks(loop)
         # Setup a patch for the asyncio logger