refactor: remove unnecessary do_not_cancel logic (#80)

* refactor: remove unnecessary `do_not_cancel` set

`do_not_cancel` was used to keep track of tasks that should not be
canceled vs. tasks that should during shutdown phase. However, this
separation had no real effect.

* test: update expected text in assertition

The expected output when tasks outlive their grace period has changed,
assert accordingly

aiorun.py

@@ -306,24 +306,16 @@ async def new_coro():
             else:
                 pending_exception_to_raise = exc
 
-    def sep():
-        tasks = all_tasks(loop=loop)
-        do_not_cancel = set()
-        for t in tasks:
-            # TODO: we don't need access to the coro. We could simply
-            # TODO: store the task itself in the weakset.
-            if t._coro in _DO_NOT_CANCEL_COROS:
-                do_not_cancel.add(t)
-
-        tasks -= do_not_cancel
+    tasks = all_tasks(loop=loop)
 
+    if tasks:
         logger.info("Cancelling pending tasks.")
         for t in tasks:
-            logger.debug("Cancelling task: %s", t)
-            t.cancel()
-        return tasks, do_not_cancel
-
-    tasks, do_not_cancel = sep()
+            # TODO: we don't need access to the coro. We could simply
+            # TODO: store the task itself in the weakset.
+            if t._coro not in _DO_NOT_CANCEL_COROS:
+                logger.debug("Cancelling task: %s", t)
+                t.cancel()
 
     async def wait_for_cancelled_tasks(timeout):
         """ Wait for the cancelled tasks to finish up. They have received
@@ -362,19 +354,19 @@ async def wait_for_cancelled_tasks(timeout):
             <snip>
 
         """
-        _, pending = await asyncio.wait([*tasks, *do_not_cancel], timeout=timeout)
+        _, pending = await asyncio.wait([*tasks], timeout=timeout)
         if pending:
             tasks_info = '\n\n'.join(str(t.get_stack()) for t in pending)
             msg = (
-                "During shutdown, the following tasks were cancelled but refused "
+                "During shutdown, the following tasks refused "
                 "to exit after {timeout} seconds: {tasks_info}".format(
                     timeout=timeout,
                     tasks_info=tasks_info
                 )
             )
             logger.warning(msg)
 
-    if tasks or do_not_cancel:
+    if tasks:
         logger.info("Running pending tasks till complete")
         # TODO: obtain all the results, and log any results that are exceptions
         # other than CancelledError. Will be useful for troubleshooting.

tests/test_stop_on_errors.py

@@ -92,7 +92,7 @@ async def main():
 
     print(excinfo.value)
     print(excinfo.traceback)
-    assert "tasks were cancelled but refused to exit after 2.0 seconds" in caplog.text
+    assert "tasks refused to exit after 2.0 seconds" in caplog.text
     assert "Stops the loop" in str(excinfo.value)
     assert all(t.cancelled for t in created_tasks)