Only send stop msg if not received from far end

tractor/_streaming.py

@@ -53,7 +53,8 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
 
     # delegate directly to underlying mem channel
     def receive_nowait(self):
-        return self._rx_chan.receive_nowait()
+        msg = self._rx_chan.receive_nowait()
+        return msg['yield']
 
     async def receive(self):
         try:
@@ -106,6 +107,7 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
             # when the send is closed we assume the stream has
             # terminated and signal this local iterator to stop
             await self.aclose()
+
             # await self._ctx.send_stop()
             raise StopAsyncIteration
 
@@ -326,10 +328,14 @@ class Context:
             try:
                 yield rchan
 
-            finally:
+            except trio.EndOfChannel:
+                raise
+
+            else:
                 # signal ``StopAsyncIteration`` on far end.
                 await self.send_stop()
 
+            finally:
                 if self._portal:
                     self._portal._streams.remove(rchan)