Use &encoding for msgpack Packer

- This commit disables automatic encoding of Unicode strings until
  &encoding is retrieved, and then resets the packer to use &encoding
- Previously the msgpack Packer always encoded Unicode as utf-8

Author: equalsraf

neovim/api/nvim.py

@@ -44,7 +44,10 @@ def from_session(cls, session):
         creating specialized objects from Nvim remote handles.
         """
         session.error_wrapper = lambda e: NvimError(e[1])
-        channel_id, metadata = session.request('vim_get_api_info')
+        channel_id, metadata = session.request(b'vim_get_api_info')
+
+        encoding = session.request(b'vim_get_option', b'encoding')
+        session._async_session._msgpack_stream.set_packer_encoding(encoding)
 
         if IS_PYTHON3:
             hook = DecodeHook()

neovim/msgpack_rpc/msgpack_stream.py

@@ -21,11 +21,15 @@ def __init__(self, event_loop):
         """Wrap `event_loop` on a msgpack-aware interface."""
         self._event_loop = event_loop
         self._posted = deque()
-        self._packer = Packer(use_bin_type=True)
+        self._packer = Packer(use_bin_type=True, encoding=None)
         self._unpacker = Unpacker()
         self._message_cb = None
         self._stopped = False
 
+    def set_packer_encoding(self, encoding):
+        """Switch encoding for Unicode strings."""
+        self._packer = Packer(use_bin_type=True, encoding=encoding)
+
     def post(self, msg):
         """Post `msg` to the read queue of the `MsgpackStream` instance.