BUG: Fix broken codemirror highlighting on file rename.

When a users uses the rename dialog in the text editor, we call
_set_mode_for_model on the returned model.  The expected model to be
returned from rename has no value for mimetype, which causes us to pass
`undefined` to `CodeMirror.findModeByMIME`, which returns `undefined`
back.  We then try access an attribute of the (undefined) return value,
causing an error.

This now properly checks whether the `mimetype` attribute is set on the
input model.

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

@@ -1,190 +1,193 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     'jquery',
     'base/js/utils',
     'codemirror/lib/codemirror',
     'codemirror/mode/meta',
     'codemirror/addon/comment/comment',
     'codemirror/addon/dialog/dialog',
     'codemirror/addon/edit/closebrackets',
     'codemirror/addon/edit/matchbrackets',
     'codemirror/addon/search/searchcursor',
     'codemirror/addon/search/search',
     'codemirror/keymap/emacs',
     'codemirror/keymap/sublime',
     'codemirror/keymap/vim',
     ],
 function($,
     utils,
     CodeMirror
 ) {
     "use strict";
 
     var Editor = function(selector, options) {
         var that = this;
         this.selector = selector;
         this.contents = options.contents;
         this.events = options.events;
         this.base_url = options.base_url;
         this.file_path = options.file_path;
         this.config = options.config;
         this.codemirror = new CodeMirror($(this.selector)[0]);
         this.generation = -1;
         
         // It appears we have to set commands on the CodeMirror class, not the
         // instance. I'd like to be wrong, but since there should only be one CM
         // instance on the page, this is good enough for now.
         CodeMirror.commands.save = $.proxy(this.save, this);
         
         this.save_enabled = false;
         
         this.config.loaded.then(function () {
             // load codemirror config
             var cfg = that.config.data.Editor || {};
             var cmopts = $.extend(true, {}, // true = recursive copy
                 Editor.default_codemirror_options,
                 cfg.codemirror_options || {}
             );
             that._set_codemirror_options(cmopts);
             that.events.trigger('config_changed.Editor', {config: that.config});
         });
     };
     
     // default CodeMirror options
     Editor.default_codemirror_options = {
         extraKeys: {
             "Tab" :  "indentMore",
         },
         indentUnit: 4,
         theme: "ipython",
         lineNumbers: true,
         lineWrapping: true,
     };
     
     Editor.prototype.load = function() {
         /** load the file */
         var that = this;
         var cm = this.codemirror;
         return this.contents.get(this.file_path, {type: 'file', format: 'text'})
             .then(function(model) {
                 cm.setValue(model.content);
 
                 // 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) {
                 that.events.trigger("file_load_failed.Editor", error);
                 if (error.xhr.responseJSON.reason === 'bad format') {
                     window.location = utils.url_path_join(
                         that.base_url,
                         'files',
                         that.file_path
                     );
                 }
                 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
-        var modeinfo = CodeMirror.findModeByMIME(model.mimetype);
-        if (modeinfo.mode === "null") {
+        var modeinfo;
+        if (model.mimetype) {
+            modeinfo = CodeMirror.findModeByMIME(model.mimetype);
+        }
+        if (!modeinfo || modeinfo.mode === "null") {
             // find by mime failed, use find by ext
             var ext_idx = model.name.lastIndexOf('.');
             
             if (ext_idx > 0) {
                 // CodeMirror.findModeByExtension wants extension without '.'
                 modeinfo = CodeMirror.findModeByExtension(model.name.slice(ext_idx + 1));
             }
         }
         if (modeinfo) {
             this.set_codemirror_mode(modeinfo);
         }
     };
     
     Editor.prototype.set_codemirror_mode = function (modeinfo) {
         /** set the codemirror mode from a modeinfo struct */
         var that = this;
         utils.requireCodeMirrorMode(modeinfo, function () {
             that.codemirror.setOption('mode', modeinfo.mode);
             that.events.trigger("mode_changed.Editor", modeinfo);
         });
     };
     
     Editor.prototype.get_filename = function () {
         return utils.url_path_split(this.file_path)[1];
     };
 
     Editor.prototype.rename = function (new_name) {
         /** rename the file */
         var that = this;
         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 (model) {
                 that.file_path = model.path;
                 that.events.trigger('file_renamed.Editor', model);
                 that._set_mode_for_model(model);
             }
         );
     };
     
     Editor.prototype.save = function () {
         /** save the file */
         if (!this.save_enabled) {
             console.log("Not saving, save disabled");
             return;
         }
         var model = {
             path: this.file_path,
             type: 'file',
             format: 'text',
             content: this.codemirror.getValue(),
         };
         var that = this;
         // record change generation for isClean
         this.generation = this.codemirror.changeGeneration();
         return this.contents.save(this.file_path, model).then(function(data) {
             that.events.trigger("file_saved.Editor", data);
         });
     };
     
     Editor.prototype._set_codemirror_options = function (options) {
         // update codemirror options from a dict
         var codemirror = this.codemirror;
         $.map(options, function (value, opt) {
             if (value === null) {
                 value = CodeMirror.defaults[opt];
             }
             codemirror.setOption(opt, value);
         });
     };
     
     Editor.prototype.update_codemirror_options = function (options) {
         /** update codemirror options locally and save changes in config */
         var that = this;
         this._set_codemirror_options(options);
         return this.config.update({
             Editor: {
                 codemirror_options: options
             }
         }).then(
             that.events.trigger('config_changed.Editor', {config: that.config})
         );
     };
 
     return {Editor: Editor};
 });