update message spec adapter per review

- docs and comments
- adapt complete_reply with `end=null`, `start=-len(matched_text)`
- remove some incorrect `status` fields
- add `handle_reply_status_error` for handling `status=error` replies (no-op, currently)

IPython/html/services/kernels/handlers.py

@@ -81,16 +81,23 b' class ZMQChannelHandler(AuthenticatedZMQStreamHandler):'
         km = self.kernel_manager
         meth = getattr(km, 'connect_%s' % self.channel)
         self.zmq_stream = meth(self.kernel_id, identity=self.session.bsession)
+        # Create a kernel_info channel to query the kernel protocol version.
+        # This channel will be closed after the kernel_info reply is received.
         self.kernel_info_channel = None
         self.kernel_info_channel = km.connect_shell(self.kernel_id)
-        self.kernel_info_channel.on_recv(self._handle_kernel_info)
+        self.kernel_info_channel.on_recv(self._handle_kernel_info_reply)
         self._request_kernel_info()
     
     def _request_kernel_info(self):
+        """send a request for kernel_info"""
         self.log.debug("requesting kernel info")
         self.session.send(self.kernel_info_channel, "kernel_info_request")
     
-    def _handle_kernel_info(self, msg):
+    def _handle_kernel_info_reply(self, msg):
+        """process the kernel_info_reply
+        
+        enabling msg spec adaptation, if necessary
+        """
         idents,msg = self.session.feed_identities(msg)
         try:
             msg = self.session.unserialize(msg)

IPython/html/static/notebook/js/completer.js

@@ -171,6 +171,15 b' var IPython = (function (IPython) {'
         var matches = content.matches;
 
         var cur = this.editor.getCursor();
+        if (end === null) {
+            // adapted message spec replies don't have cursor position info,
+            // interpret end=null as current position,
+            // and negative start relative to that
+            end = utils.to_absolute_cursor_pos(this.editor, cur);
+            if (start < 0) {
+                start = end + start;
+            }
+        }
         var results = CodeMirror.contextHint(this.editor);
         var filtered_results = [];
         //remove results from context completion

IPython/kernel/adapter.py

@@ -5,7 +5,7 b''
 
 import json
 
-from IPython.core.release import kernel_protocol_version, kernel_protocol_version_info
+from IPython.core.release import kernel_protocol_version_info
 from IPython.utils.tokenutil import token_at_cursor
 
 
@@ -45,6 +45,13 b' class Adapter(object):'
             msg['msg_type'] = header['msg_type'] = self.msg_type_map[msg_type]
         return msg
     
+    def handle_reply_status_error(msg):
+        """This will be called *instead of* the regular handler
+        
+        on any reply with status != ok
+        """
+        return msg
+    
     def __call__(self, msg):
         msg = self.update_header(msg)
         msg = self.update_metadata(msg)
@@ -54,9 +61,10 b' class Adapter(object):'
         handler = getattr(self, header['msg_type'], None)
         if handler is None:
             return msg
-        # no transform for status=error
+        
+        # handle status=error replies separately (no change, at present)
         if msg['content'].get('status', None) in {'error', 'aborted'}:
-            return msg
+            return self.handle_reply_status_error(msg)
         return handler(msg)
 
 def _version_str_to_list(version):
@@ -143,7 +151,7 b' class V5toV4(Adapter):'
         cursor_pos = content['cursor_pos']
         line, _ = code_to_line(code, cursor_pos)
         
-        new_content = msg['content'] = {'status' : 'ok'}
+        new_content = msg['content'] = {}
         new_content['oname'] = token_at_cursor(code, cursor_pos)
         new_content['detail_level'] = content['detail_level']
         return msg
@@ -173,12 +181,10 b' class V5toV4(Adapter):'
         msg['content'].pop('password', None)
         return msg
 
-def _tuple_to_str(version):
-    return ".".join(map(str, version))
 
 class V4toV5(Adapter):
     """Convert msg spec V4 to V5"""
-    version = kernel_protocol_version
+    version = '5.0'
     
     # invert message renames above
     msg_type_map = {v:k for k,v in V5toV4.msg_type_map.items()}
@@ -227,13 +233,14 b' class V4toV5(Adapter):'
         return msg
     
     def complete_reply(self, msg):
-        # TODO: complete_reply needs more context than we have
-        # Maybe strip common prefix and give magic cursor_start = cursor_end = 0?
+        # complete_reply needs more context than we have to get cursor_start and end.
+        # use special value of `-1` to indicate to frontend that it should be at
+        # the current cursor position.
         content = msg['content']
         new_content = msg['content'] = {'status' : 'ok'}
-        n = len(content['matched_text'])
-        new_content['matches'] = [ m[n:] for m in content['matches'] ]
-        new_content['cursor_start'] = new_content['cursor_end'] = 0
+        new_content['matches'] = content['matches']
+        new_content['cursor_start'] = -len(content['matched_text'])
+        new_content['cursor_end'] = None
         new_content['metadata'] = {}
         return msg
     

IPython/kernel/tests/test_adapter.py

@@ -114,13 +114,11 b' class V4toV5TestCase(AdapterTest):'
         v4, v5 = self.adapt(msg)
         v4c = v4['content']
         v5c = v5['content']
-        n = len(v4c['matched_text'])
-        expected_matches = [ m[n:] for m in v4c['matches'] ]
         
-        self.assertEqual(v5c['matches'], expected_matches)
+        self.assertEqual(v5c['matches'], v4c['matches'])
         self.assertEqual(v5c['metadata'], {})
-        self.assertEqual(v5c['cursor_start'], 0)
-        self.assertEqual(v5c['cursor_end'], 0)
+        self.assertEqual(v5c['cursor_start'], -4)
+        self.assertEqual(v5c['cursor_end'], None)
     
     def test_object_info_request(self):
         msg = self.msg("object_info_request", {