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, 6 insertions, 0 deletions

diff --git a/asyncio/transports.py b/asyncio/transports.py
index 70b323f..5540f7e 100644
--- a/asyncio/transports.py
+++ b/asyncio/transports.py
@@ -14,6 +14,7 @@ class BaseTransport:
         if extra is None:
             extra = {}
         self._extra = extra
+        self._closing = False
 
     def get_extra_info(self, name, default=None):
         """Get optional transport information."""
@@ -29,6 +30,11 @@ class BaseTransport:
         """
         raise NotImplementedError
 
+    @property
+    def closing(self):
+        """Is the transport being closed?"""
+        return self._closing
+
 
 class ReadTransport(BaseTransport):
     """Interface for read-only transports."""