Merge `ReceiveMsgStream` and `MsgStream`

Since one-way streaming can be accomplished by just *not* sending on one
side (and/or thus wrapping such usage in a more restrictive API), we
just drop the recv-only parent type. The only method different was
`MsgStream.send()`, now merged in. Further in usage of `.subscribe()`
we monkey patch the underlying stream's `.send()` onto the delivered
broadcast receiver so that subscriber tasks can two-way stream as though
using the stream directly.

This allows us to more definitively drop `tractor.open_stream_from()` in
the longer run if we so choose as well; note currently this will
potentially create an issue if a caller tries to `.send()` on such a one
way stream.

tractor/__init__.py

@@ -24,7 +24,6 @@ from ._clustering import open_actor_cluster
 from ._ipc import Channel
 from ._streaming import (
     Context,
-    ReceiveMsgStream,
     MsgStream,
     stream,
     context,
@@ -64,7 +63,6 @@ __all__ = [
     'MsgStream',
     'BaseExceptionGroup',
     'Portal',
-    'ReceiveMsgStream',
     'RemoteActorError',
     'breakpoint',
     'context',

tractor/_portal.py

@@ -45,7 +45,10 @@ from ._exceptions import (
     NoResult,
     ContextCancelled,
 )
-from ._streaming import Context, ReceiveMsgStream
+from ._streaming import (
+    Context,
+    MsgStream,
+)
 
 
 log = get_logger(__name__)
@@ -101,7 +104,7 @@ class Portal:
         # it is expected that ``result()`` will be awaited at some
         # point.
         self._expect_result: Optional[Context] = None
-        self._streams: set[ReceiveMsgStream] = set()
+        self._streams: set[MsgStream] = set()
         self.actor = current_actor()
 
     async def _submit_for_result(
@@ -316,7 +319,7 @@ class Portal:
         async_gen_func: Callable,  # typing: ignore
         **kwargs,
 
-    ) -> AsyncGenerator[ReceiveMsgStream, None]:
+    ) -> AsyncGenerator[MsgStream, None]:
 
         if not inspect.isasyncgenfunction(async_gen_func):
             if not (
@@ -341,7 +344,7 @@ class Portal:
 
         try:
             # deliver receive only stream
-            async with ReceiveMsgStream(
+            async with MsgStream(
                 ctx, ctx._recv_chan,
             ) as rchan:
                 self._streams.add(rchan)

tractor/_streaming.py

@@ -50,12 +50,13 @@ log = get_logger(__name__)
 # - use __slots__ on ``Context``?
 
 
-class ReceiveMsgStream(trio.abc.ReceiveChannel):
+class MsgStream(trio.abc.Channel):
     '''
-    A IPC message stream for receiving logically sequenced values over
-    an inter-actor ``Channel``. This is the type returned to a local
-    task which entered either ``Portal.open_stream_from()`` or
-    ``Context.open_stream()``.
+    A bidirectional message stream for receiving logically sequenced
+    values over an inter-actor IPC ``Channel``.
+
+    This is the type returned to a local task which entered either
+    ``Portal.open_stream_from()`` or ``Context.open_stream()``.
 
     Termination rules:
 
@@ -317,15 +318,15 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
         async with self._broadcaster.subscribe() as bstream:
             assert bstream.key != self._broadcaster.key
             assert bstream._recv == self._broadcaster._recv
+
+            # NOTE: we patch on a `.send()` to the bcaster so that the
+            # caller can still conduct 2-way streaming using this
+            # ``bstream`` handle transparently as though it was the msg
+            # stream instance.
+            bstream.send = self.send
+
             yield bstream
 
-
-class MsgStream(ReceiveMsgStream, trio.abc.Channel):
-    '''
-    Bidirectional message stream for use within an inter-actor actor
-    ``Context```.
-
-    '''
     async def send(
         self,
         data: Any