update mode on rename

IPython/html/static/edit/js/editor.js

@@ -73,6 +73,21 b' function($,'
                 // Setting the file's initial value creates a history entry,
                 // which we don't want.
                 cm.clearHistory();
+                that._set_mode_for_model(model);
+                that.save_enabled = true;
+                that.generation = cm.changeGeneration();
+                that.events.trigger("file_loaded.Editor", model);
+            },
+            function(error) {
+                cm.setValue("Error! " + error.message +
+                                "\nSaving disabled.");
+                that.save_enabled = false;
+            }
+        );
+    };
+
+    Editor.prototype._set_mode_for_model = function (model) {
+        /** Set the CodeMirror mode based on the file model */
 
                 // Find and load the highlighting mode,
                 // first by mime-type, then by file extension
@@ -87,18 +102,8 b' function($,'
                     }
                 }
                 if (modeinfo) {
-                    that.set_codemirror_mode(modeinfo);
+            this.set_codemirror_mode(modeinfo);
                 }
-                that.save_enabled = true;
-                that.generation = cm.changeGeneration();
-                that.events.trigger("file_loaded.Editor", model);
-            },
-            function(error) {
-                cm.setValue("Error! " + error.message +
-                                "\nSaving disabled.");
-                that.save_enabled = false;
-            }
-        );
     };
     
     Editor.prototype.set_codemirror_mode = function (modeinfo) {
@@ -120,9 +125,10 b' function($,'
         var parent = utils.url_path_split(this.file_path)[0];
         var new_path = utils.url_path_join(parent, new_name);
         return this.contents.rename(this.file_path, new_path).then(
-            function (json) {
-                that.file_path = json.path;
-                that.events.trigger('file_renamed.Editor', json);
+            function (model) {
+                that.file_path = model.path;
+                that.events.trigger('file_renamed.Editor', model);
+                that._set_mode_for_model(model);
             }
         );
     };