Add closing read-only property to transportsclosing

* Disallow write() on closing transports
* Disallow aslo calling pause_writing() and resume_writing() on
  StreamReaderProtocol if the transport is closing

1 files changed, 11 insertions, 0 deletions

diff --git a/asyncio/streams.py b/asyncio/streams.py
index 6484c43..409b2f9 100644
--- a/asyncio/streams.py
+++ b/asyncio/streams.py
@@ -153,15 +153,25 @@ class FlowControlMixin(protocols.Protocol):
         self._paused = False
         self._drain_waiter = None
         self._connection_lost = False
+        self._transport = None
+
+    def connection_made(self, transport):
+        self._transport = transport
 
     def pause_writing(self):
         assert not self._paused
+        if self._transport is not None and self._transport.closing:
+            raise RuntimeError('Cannot call pause_writing() '
+                               'on closing or closed transport')
         self._paused = True
         if self._loop.get_debug():
             logger.debug("%r pauses writing", self)
 
     def resume_writing(self):
         assert self._paused
+        if self._transport is not None and self._transport.closing:
+            raise RuntimeError('Cannot call resume_writing() '
+                               'on closing or closed transport')
         self._paused = False
         if self._loop.get_debug():
             logger.debug("%r resumes writing", self)
@@ -217,6 +227,7 @@ class StreamReaderProtocol(FlowControlMixin, protocols.Protocol):
         self._client_connected_cb = client_connected_cb
 
     def connection_made(self, transport):
+        super().connection_made(transport)
         self._stream_reader.set_transport(transport)
         if self._client_connected_cb is not None:
             self._stream_writer = StreamWriter(transport, self,