asyncio: sync with Tulip

* Tulip issue 184: FlowControlMixin constructor now get the event loop if the
  loop parameter is not set. Add unit tests to ensure that constructor of
  StreamReader and StreamReaderProtocol classes get the event loop.
* Remove outdated TODO/XXX

Lib/asyncio/futures.py

@@ -20,7 +20,6 @@ _FINISHED = 'FINISHED'
 
 _PY34 = sys.version_info >= (3, 4)
 
-# TODO: Do we really want to depend on concurrent.futures internals?
 Error = concurrent.futures._base.Error
 CancelledError = concurrent.futures.CancelledError
 TimeoutError = concurrent.futures.TimeoutError
@@ -30,7 +29,6 @@ STACK_DEBUG = logging.DEBUG - 1  # heavy-duty debugging
 
 class InvalidStateError(Error):
     """The operation is not allowed in this state."""
-    # TODO: Show the future, its state, the method, and the required state.
 
 
 class _TracebackLogger:

Lib/asyncio/proactor_events.py

@@ -487,7 +487,8 @@ class BaseProactorEventLoop(base_events.BaseEventLoop):
         self.call_soon(loop)
 
     def _process_events(self, event_list):
-        pass    # XXX hard work currently done in poll
+        # Events are processed in the IocpProactor._poll() method
+        pass
 
     def _stop_accept_futures(self):
         for future in self._accept_futures.values():

Lib/asyncio/selector_events.py

@@ -145,7 +145,6 @@ class BaseSelectorEventLoop(base_events.BaseEventLoop):
             pass  # False alarm.
         except OSError as exc:
             # There's nowhere to send the error, so just log it.
-            # TODO: Someone will want an error handler for this.
             if exc.errno in (errno.EMFILE, errno.ENFILE,
                              errno.ENOBUFS, errno.ENOMEM):
                 # Some platforms (e.g. Linux keep reporting the FD as

Lib/asyncio/streams.py

@@ -145,7 +145,10 @@ class FlowControlMixin(protocols.Protocol):
     """
 
     def __init__(self, loop=None):
-        self._loop = loop  # May be None; we may never need it.
+        if loop is None:
+            self._loop = events.get_event_loop()
+        else:
+            self._loop = loop
         self._paused = False
         self._drain_waiter = None
         self._connection_lost = False
@@ -306,8 +309,9 @@ class StreamReader:
         # it also doubles as half the buffer limit.
         self._limit = limit
         if loop is None:
-            loop = events.get_event_loop()
-        self._loop = loop
+            self._loop = events.get_event_loop()
+        else:
+            self._loop = loop
         self._buffer = bytearray()
         self._eof = False  # Whether we're done.
         self._waiter = None  # A future.

Lib/asyncio/unix_events.py

@@ -496,9 +496,6 @@ class _UnixWritePipeTransport(transports._FlowControlMixin,
     def can_write_eof(self):
         return True
 
-    # TODO: Make the relationships between write_eof(), close(),
-    # abort(), _fatal_error() and _close() more straightforward.
-
     def write_eof(self):
         if self._closing:
             return
@@ -897,7 +894,7 @@ class FastChildWatcher(BaseChildWatcher):
 
 
 class _UnixDefaultEventLoopPolicy(events.BaseDefaultEventLoopPolicy):
-    """XXX"""
+    """UNIX event loop policy with a watcher for child processes."""
     _loop_factory = _UnixSelectorEventLoop
 
     def __init__(self):

Lib/test/test_asyncio/test_streams.py

@@ -625,6 +625,25 @@ os.close(fd)
         data = self.loop.run_until_complete(reader.read(-1))
         self.assertEqual(data, b'data')
 
+    def test_streamreader_constructor(self):
+        self.addCleanup(asyncio.set_event_loop, None)
+        asyncio.set_event_loop(self.loop)
+
+        # Tulip issue #184: Ensure that StreamReaderProtocol constructor
+        # retrieves the current loop if the loop parameter is not set
+        reader = asyncio.StreamReader()
+        self.assertIs(reader._loop, self.loop)
+
+    def test_streamreaderprotocol_constructor(self):
+        self.addCleanup(asyncio.set_event_loop, None)
+        asyncio.set_event_loop(self.loop)
+
+        # Tulip issue #184: Ensure that StreamReaderProtocol constructor
+        # retrieves the current loop if the loop parameter is not set
+        reader = mock.Mock()
+        protocol = asyncio.StreamReaderProtocol(reader)
+        self.assertIs(protocol._loop, self.loop)
+
 
 if __name__ == '__main__':
     unittest.main()