Don't throw Errors with Objects as the message/

IPython/html/static/base/js/utils.js

@@ -1,764 +1,761
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     'base/js/namespace',
     'jquery',
     'codemirror/lib/codemirror',
     'rsvp',
 ], function(IPython, $, CodeMirror, rsvp){
     "use strict";
     
     IPython.load_extensions = function () {
         // load one or more IPython notebook extensions with requirejs
         
         var extensions = [];
         var extension_names = arguments;
         for (var i = 0; i < extension_names.length; i++) {
             extensions.push("nbextensions/" + arguments[i]);
         }
         
         require(extensions,
             function () {
                 for (var i = 0; i < arguments.length; i++) {
                     var ext = arguments[i];
                     var ext_name = extension_names[i];
                     // success callback
                     console.log("Loaded extension: " + ext_name);
                     if (ext && ext.load_ipython_extension !== undefined) {
                         ext.load_ipython_extension();
                     }
                 }
             },
             function (err) {
                 // failure callback
                 console.log("Failed to load extension(s):", err.requireModules, err);
             }
         );
     };
 
     //============================================================================
     // Cross-browser RegEx Split
     //============================================================================
 
     // This code has been MODIFIED from the code licensed below to not replace the
     // default browser split.  The license is reproduced here.
 
     // see http://blog.stevenlevithan.com/archives/cross-browser-split for more info:
     /*!
      * Cross-Browser Split 1.1.1
      * Copyright 2007-2012 Steven Levithan <stevenlevithan.com>
      * Available under the MIT License
      * ECMAScript compliant, uniform cross-browser split method
      */
 
     /**
      * Splits a string into an array of strings using a regex or string
      * separator. Matches of the separator are not included in the result array.
      * However, if `separator` is a regex that contains capturing groups,
      * backreferences are spliced into the result each time `separator` is
      * matched. Fixes browser bugs compared to the native
      * `String.prototype.split` and can be used reliably cross-browser.
      * @param {String} str String to split.
      * @param {RegExp|String} separator Regex or string to use for separating
      *     the string.
      * @param {Number} [limit] Maximum number of items to include in the result
      *     array.
      * @returns {Array} Array of substrings.
      * @example
      *
      * // Basic use
      * regex_split('a b c d', ' ');
      * // -> ['a', 'b', 'c', 'd']
      *
      * // With limit
      * regex_split('a b c d', ' ', 2);
      * // -> ['a', 'b']
      *
      * // Backreferences in result array
      * regex_split('..word1 word2..', /([a-z]+)(\d+)/i);
      * // -> ['..', 'word', '1', ' ', 'word', '2', '..']
      */
     var regex_split = function (str, separator, limit) {
         // If `separator` is not a regex, use `split`
         if (Object.prototype.toString.call(separator) !== "[object RegExp]") {
             return split.call(str, separator, limit);
         }
         var output = [],
             flags = (separator.ignoreCase ? "i" : "") +
                     (separator.multiline  ? "m" : "") +
                     (separator.extended   ? "x" : "") + // Proposed for ES6
                     (separator.sticky     ? "y" : ""), // Firefox 3+
             lastLastIndex = 0,
             // Make `global` and avoid `lastIndex` issues by working with a copy
             separator = new RegExp(separator.source, flags + "g"),
             separator2, match, lastIndex, lastLength;
         str += ""; // Type-convert
 
         var compliantExecNpcg = typeof(/()??/.exec("")[1]) === "undefined";
         if (!compliantExecNpcg) {
             // Doesn't need flags gy, but they don't hurt
             separator2 = new RegExp("^" + separator.source + "$(?!\\s)", flags);
         }
         /* Values for `limit`, per the spec:
          * If undefined: 4294967295 // Math.pow(2, 32) - 1
          * If 0, Infinity, or NaN: 0
          * If positive number: limit = Math.floor(limit); if (limit > 4294967295) limit -= 4294967296;
          * If negative number: 4294967296 - Math.floor(Math.abs(limit))
          * If other: Type-convert, then use the above rules
          */
         limit = typeof(limit) === "undefined" ?
             -1 >>> 0 : // Math.pow(2, 32) - 1
             limit >>> 0; // ToUint32(limit)
         while (match = separator.exec(str)) {
             // `separator.lastIndex` is not reliable cross-browser
             lastIndex = match.index + match[0].length;
             if (lastIndex > lastLastIndex) {
                 output.push(str.slice(lastLastIndex, match.index));
                 // Fix browsers whose `exec` methods don't consistently return `undefined` for
                 // nonparticipating capturing groups
                 if (!compliantExecNpcg && match.length > 1) {
                     match[0].replace(separator2, function () {
                         for (var i = 1; i < arguments.length - 2; i++) {
                             if (typeof(arguments[i]) === "undefined") {
                                 match[i] = undefined;
                             }
                         }
                     });
                 }
                 if (match.length > 1 && match.index < str.length) {
                     Array.prototype.push.apply(output, match.slice(1));
                 }
                 lastLength = match[0].length;
                 lastLastIndex = lastIndex;
                 if (output.length >= limit) {
                     break;
                 }
             }
             if (separator.lastIndex === match.index) {
                 separator.lastIndex++; // Avoid an infinite loop
             }
         }
         if (lastLastIndex === str.length) {
             if (lastLength || !separator.test("")) {
                 output.push("");
             }
         } else {
             output.push(str.slice(lastLastIndex));
         }
         return output.length > limit ? output.slice(0, limit) : output;
     };
 
     //============================================================================
     // End contributed Cross-browser RegEx Split
     //============================================================================
 
 
     var uuid = function () {
         // http://www.ietf.org/rfc/rfc4122.txt
         var s = [];
         var hexDigits = "0123456789ABCDEF";
         for (var i = 0; i < 32; i++) {
             s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1);
         }
         s[12] = "4";  // bits 12-15 of the time_hi_and_version field to 0010
         s[16] = hexDigits.substr((s[16] & 0x3) | 0x8, 1);  // bits 6-7 of the clock_seq_hi_and_reserved to 01
 
         var uuid = s.join("");
         return uuid;
     };
 
 
     //Fix raw text to parse correctly in crazy XML
     function xmlencode(string) {
         return string.replace(/\&/g,'&'+'amp;')
             .replace(/</g,'&'+'lt;')
             .replace(/>/g,'&'+'gt;')
             .replace(/\'/g,'&'+'apos;')
             .replace(/\"/g,'&'+'quot;')
             .replace(/`/g,'&'+'#96;');
     }
 
 
     //Map from terminal commands to CSS classes
     var ansi_colormap = {
         "01":"ansibold",
         
         "30":"ansiblack",
         "31":"ansired",
         "32":"ansigreen",
         "33":"ansiyellow",
         "34":"ansiblue",
         "35":"ansipurple",
         "36":"ansicyan",
         "37":"ansigray",
         
         "40":"ansibgblack",
         "41":"ansibgred",
         "42":"ansibggreen",
         "43":"ansibgyellow",
         "44":"ansibgblue",
         "45":"ansibgpurple",
         "46":"ansibgcyan",
         "47":"ansibggray"
     };
     
     function _process_numbers(attrs, numbers) {
         // process ansi escapes
         var n = numbers.shift();
         if (ansi_colormap[n]) {
             if ( ! attrs["class"] ) {
                 attrs["class"] = ansi_colormap[n];
             } else {
                 attrs["class"] += " " + ansi_colormap[n];
             }
         } else if (n == "38" || n == "48") {
             // VT100 256 color or 24 bit RGB
             if (numbers.length < 2) {
                 console.log("Not enough fields for VT100 color", numbers);
                 return;
             }
             
             var index_or_rgb = numbers.shift();
             var r,g,b;
             if (index_or_rgb == "5") {
                 // 256 color
                 var idx = parseInt(numbers.shift());
                 if (idx < 16) {
                     // indexed ANSI
                     // ignore bright / non-bright distinction
                     idx = idx % 8;
                     var ansiclass = ansi_colormap[n[0] + (idx % 8).toString()];
                     if ( ! attrs["class"] ) {
                         attrs["class"] = ansiclass;
                     } else {
                         attrs["class"] += " " + ansiclass;
                     }
                     return;
                 } else if (idx < 232) {
                     // 216 color 6x6x6 RGB
                     idx = idx - 16;
                     b = idx % 6;
                     g = Math.floor(idx / 6) % 6;
                     r = Math.floor(idx / 36) % 6;
                     // convert to rgb
                     r = (r * 51);
                     g = (g * 51);
                     b = (b * 51);
                 } else {
                     // grayscale
                     idx = idx - 231;
                     // it's 1-24 and should *not* include black or white,
                     // so a 26 point scale
                     r = g = b = Math.floor(idx * 256 / 26);
                 }
             } else if (index_or_rgb == "2") {
                 // Simple 24 bit RGB
                 if (numbers.length > 3) {
                     console.log("Not enough fields for RGB", numbers);
                     return;
                 }
                 r = numbers.shift();
                 g = numbers.shift();
                 b = numbers.shift();
             } else {
                 console.log("unrecognized control", numbers);
                 return;
             }
             if (r !== undefined) {
                 // apply the rgb color
                 var line;
                 if (n == "38") {
                     line = "color: ";
                 } else {
                     line = "background-color: ";
                 }
                 line = line + "rgb(" + r + "," + g + "," + b + ");";
                 if ( !attrs.style ) {
                     attrs.style = line;
                 } else {
                     attrs.style += " " + line;
                 }
             }
         }
     }
 
     function ansispan(str) {
         // ansispan function adapted from github.com/mmalecki/ansispan (MIT License)
         // regular ansi escapes (using the table above)
         var is_open = false;
         return str.replace(/\033\[(0?[01]|22|39)?([;\d]+)?m/g, function(match, prefix, pattern) {
             if (!pattern) {
                 // [(01|22|39|)m close spans
                 if (is_open) {
                     is_open = false;
                     return "</span>";
                 } else {
                     return "";
                 }
             } else {
                 is_open = true;
 
                 // consume sequence of color escapes
                 var numbers = pattern.match(/\d+/g);
                 var attrs = {};
                 while (numbers.length > 0) {
                     _process_numbers(attrs, numbers);
                 }
 
                 var span = "<span ";
                 for (var attr in attrs) {
                     var value = attrs[attr];
                     span = span + " " + attr + '="' + attrs[attr] + '"';
                 }
                 return span + ">";
             }
         });
     }
 
     // Transform ANSI color escape codes into HTML <span> tags with css
     // classes listed in the above ansi_colormap object. The actual color used
     // are set in the css file.
     function fixConsole(txt) {
         txt = xmlencode(txt);
         var re = /\033\[([\dA-Fa-f;]*?)m/;
         var opened = false;
         var cmds = [];
         var opener = "";
         var closer = "";
 
         // Strip all ANSI codes that are not color related.  Matches
         // all ANSI codes that do not end with "m".
         var ignored_re = /(?=(\033\[[\d;=]*[a-ln-zA-Z]{1}))\1(?!m)/g;
         txt = txt.replace(ignored_re, "");
         
         // color ansi codes
         txt = ansispan(txt);
         return txt;
     }
 
     // Remove chunks that should be overridden by the effect of
     // carriage return characters
     function fixCarriageReturn(txt) {
         var tmp = txt;
         do {
             txt = tmp;
             tmp = txt.replace(/\r+\n/gm, '\n'); // \r followed by \n --> newline
             tmp = tmp.replace(/^.*\r+/gm, '');  // Other \r --> clear line
         } while (tmp.length < txt.length);
         return txt;
     }
 
     // Locate any URLs and convert them to a anchor tag
     function autoLinkUrls(txt) {
         return txt.replace(/(^|\s)(https?|ftp)(:[^'">\s]+)/gi,
             "$1<a target=\"_blank\" href=\"$2$3\">$2$3</a>");
     }
 
     var points_to_pixels = function (points) {
         // A reasonably good way of converting between points and pixels.
         var test = $('<div style="display: none; width: 10000pt; padding:0; border:0;"></div>');
         $(body).append(test);
         var pixel_per_point = test.width()/10000;
         test.remove();
         return Math.floor(points*pixel_per_point);
     };
     
     var always_new = function (constructor) {
         // wrapper around contructor to avoid requiring `var a = new constructor()`
         // useful for passing constructors as callbacks,
         // not for programmer laziness.
         // from http://programmers.stackexchange.com/questions/118798
         return function () {
             var obj = Object.create(constructor.prototype);
             constructor.apply(obj, arguments);
             return obj;
         };
     };
 
     var url_path_join = function () {
         // join a sequence of url components with '/'
         var url = '';
         for (var i = 0; i < arguments.length; i++) {
             if (arguments[i] === '') {
                 continue;
             }
             if (url.length > 0 && url[url.length-1] != '/') {
                 url = url + '/' + arguments[i];
             } else {
                 url = url + arguments[i];
             }
         }
         url = url.replace(/\/\/+/, '/');
         return url;
     };
     
     var url_path_split = function (path) {
         // Like os.path.split for URLs.
         // Always returns two strings, the directory path and the base filename
         
         var idx = path.lastIndexOf('/');
         if (idx === -1) {
             return ['', path];
         } else {
             return [ path.slice(0, idx), path.slice(idx + 1) ];
         }
     };
     
     var parse_url = function (url) {
         // an `a` element with an href allows attr-access to the parsed segments of a URL
         // a = parse_url("http://localhost:8888/path/name#hash")
         // a.protocol = "http:"
         // a.host     = "localhost:8888"
         // a.hostname = "localhost"
         // a.port     = 8888
         // a.pathname = "/path/name"
         // a.hash     = "#hash"
         var a = document.createElement("a");
         a.href = url;
         return a;
     };
     
     var encode_uri_components = function (uri) {
         // encode just the components of a multi-segment uri,
         // leaving '/' separators
         return uri.split('/').map(encodeURIComponent).join('/');
     };
     
     var url_join_encode = function () {
         // join a sequence of url components with '/',
         // encoding each component with encodeURIComponent
         return encode_uri_components(url_path_join.apply(null, arguments));
     };
 
 
     var splitext = function (filename) {
         // mimic Python os.path.splitext
         // Returns ['base', '.ext']
         var idx = filename.lastIndexOf('.');
         if (idx > 0) {
             return [filename.slice(0, idx), filename.slice(idx)];
         } else {
             return [filename, ''];
         }
     };
 
 
     var escape_html = function (text) {
         // escape text to HTML
         return $("<div/>").text(text).html();
     };
 
 
     var get_body_data = function(key) {
         // get a url-encoded item from body.data and decode it
         // we should never have any encoded URLs anywhere else in code
         // until we are building an actual request
         return decodeURIComponent($('body').data(key));
     };
     
     var to_absolute_cursor_pos = function (cm, cursor) {
         // get the absolute cursor position from CodeMirror's col, ch
         if (!cursor) {
             cursor = cm.getCursor();
         }
         var cursor_pos = cursor.ch;
         for (var i = 0; i < cursor.line; i++) {
             cursor_pos += cm.getLine(i).length + 1;
         }
         return cursor_pos;
     };
     
     var from_absolute_cursor_pos = function (cm, cursor_pos) {
         // turn absolute cursor postion into CodeMirror col, ch cursor
         var i, line;
         var offset = 0;
         for (i = 0, line=cm.getLine(i); line !== undefined; i++, line=cm.getLine(i)) {
             if (offset + line.length < cursor_pos) {
                 offset += line.length + 1;
             } else {
                 return {
                     line : i,
                     ch : cursor_pos - offset,
                 };
             }
         }
         // reached end, return endpoint
         return {
             ch : line.length - 1,
             line : i - 1,
         };
     };
     
     // http://stackoverflow.com/questions/2400935/browser-detection-in-javascript
     var browser = (function() {
         if (typeof navigator === 'undefined') {
             // navigator undefined in node
             return 'None';
         }
         var N= navigator.appName, ua= navigator.userAgent, tem;
         var M= ua.match(/(opera|chrome|safari|firefox|msie)\/?\s*(\.?\d+(\.\d+)*)/i);
         if (M && (tem= ua.match(/version\/([\.\d]+)/i)) !== null) M[2]= tem[1];
         M= M? [M[1], M[2]]: [N, navigator.appVersion,'-?'];
         return M;
     })();
 
     // http://stackoverflow.com/questions/11219582/how-to-detect-my-browser-version-and-operating-system-using-javascript
     var platform = (function () {
         if (typeof navigator === 'undefined') {
             // navigator undefined in node
             return 'None';
         }
         var OSName="None";
         if (navigator.appVersion.indexOf("Win")!=-1) OSName="Windows";
         if (navigator.appVersion.indexOf("Mac")!=-1) OSName="MacOS";
         if (navigator.appVersion.indexOf("X11")!=-1) OSName="UNIX";
         if (navigator.appVersion.indexOf("Linux")!=-1) OSName="Linux";
         return OSName;
     })();
 
     var is_or_has = function (a, b) {
         // Is b a child of a or a itself?
         return a.has(b).length !==0 || a.is(b);
     };
 
     var is_focused = function (e) {
         // Is element e, or one of its children focused?
         e = $(e);
         var target = $(document.activeElement);
         if (target.length > 0) {
             if (is_or_has(e, target)) {
                 return true;
             } else {
                 return false;
             }
         } else {
             return false;
         }
     };
     
     var mergeopt = function(_class, options, overwrite){
         options = options || {};
         overwrite = overwrite || {};
         return $.extend(true, {}, _class.options_default, options, overwrite);
     };
     
     var ajax_error_msg = function (jqXHR) {
         // Return a JSON error message if there is one,
         // otherwise the basic HTTP status text.
         if (jqXHR.responseJSON && jqXHR.responseJSON.traceback) {
             return jqXHR.responseJSON.traceback;
         } else if (jqXHR.responseJSON && jqXHR.responseJSON.message) {
             return jqXHR.responseJSON.message;
         } else {
             return jqXHR.statusText;
         }
     };
     var log_ajax_error = function (jqXHR, status, error) {
         // log ajax failures with informative messages
         var msg = "API request failed (" + jqXHR.status + "): ";
         console.log(jqXHR);
         msg += ajax_error_msg(jqXHR);
         console.log(msg);
     };
     
     var requireCodeMirrorMode = function (mode, callback, errback) {
         // load a mode with requirejs
         if (typeof mode != "string") mode = mode.name;
         if (CodeMirror.modes.hasOwnProperty(mode)) {
             callback(CodeMirror.modes.mode);
             return;
         }
         require([
                 // might want to use CodeMirror.modeURL here
                 ['codemirror/mode', mode, mode].join('/'),
             ], callback, errback
         );
     };
     
     /** Error type for wrapped XHR errors. */
     var XHR_ERROR = 'XhrError';
     
     /**
      * Wraps an AJAX error as an Error object.
      */
     var wrap_ajax_error = function (jqXHR, status, error) {
         var wrapped_error = new Error(ajax_error_msg(jqXHR));
         wrapped_error.name =  XHR_ERROR;
         // provide xhr response
         wrapped_error.xhr = jqXHR;
         wrapped_error.xhr_status = status;
         wrapped_error.xhr_error = error;
         return wrapped_error;
     };
     
     var promising_ajax = function(url, settings) {
         // Like $.ajax, but returning an ES6 promise. success and error settings
         // will be ignored.
         return new Promise(function(resolve, reject) {
             settings.success = function(data, status, jqXHR) {
                 resolve(data);
             };
             settings.error = function(jqXHR, status, error) {
                 log_ajax_error(jqXHR, status, error);
                 reject(wrap_ajax_error(jqXHR, status, error));
             };
             $.ajax(url, settings);
         });
     };
 
     var WrappedError = function(message, error){
         // Wrappable Error class
 
         // The Error class doesn't actually act on `this`.  Instead it always
         // returns a new instance of Error.  Here we capture that instance so we
         // can apply it's properties to `this`.
         var tmp = Error.apply(this, [message]);
 
         // Copy the properties of the error over to this.
         var properties = Object.getOwnPropertyNames(tmp);
         for (var i = 0; i < properties.length; i++) {
             this[properties[i]] = tmp[properties[i]];
         }
 
         // Keep a stack of the original error messages.
         if (error instanceof WrappedError) {
             this.error_stack = error.error_stack;
         } else {
             this.error_stack = [error];
         }
         this.error_stack.push(tmp);
 
         return this;
     };
 
     WrappedError.prototype = Object.create(Error.prototype, {});
 
 
     var load_class = function(class_name, module_name, registry) {
         // Tries to load a class
         //
         // Tries to load a class from a module using require.js, if a module 
         // is specified, otherwise tries to load a class from the global 
         // registry, if the global registry is provided.
         return new rsvp.Promise(function(resolve, reject) {
 
             // Try loading the view module using require.js
             if (module_name) {
                 require([module_name], function(module) {
                     if (module[class_name] === undefined) {
                         reject(new Error('Class '+class_name+' not found in module '+module_name));
                     } else {
                         resolve(module[class_name]);
                     }
                 }, reject);
             } else {
                 if (registry && registry[class_name]) {
                     resolve(registry[class_name]);
                 } else {
-                    reject(new Error({
-                        message: 'Class '+class_name+' not found in registry ', 
-                        registry: registry
-                    }));
+                    reject(new Error('Class '+class_name+' not found in registry '));
                 }
             }
         });
     };
 
     var resolve_dict = function(d) {
         // Resolve a promiseful dictionary.
         // Returns a single rsvp.Promise.
         var keys = Object.keys(d);
         var values = [];
         keys.forEach(function(key) {
             values.push(d[key]);
         });
         return rsvp.Promise.all(values).then(function(v) {
             d = {};
             for(var i=0; i<keys.length; i++) {
                 d[keys[i]] = v[i];
             }
             return d;
         });
     };
 
     var WrappedError = function(message, error){
         // Wrappable Error class
 
         // The Error class doesn't actually act on `this`.  Instead it always
         // returns a new instance of Error.  Here we capture that instance so we
         // can apply it's properties to `this`.
         var tmp = Error.apply(this, [message]);
 
         // Copy the properties of the error over to this.
         var properties = Object.getOwnPropertyNames(tmp);
         for (var i = 0; i < properties.length; i++) {
             this[properties[i]] = tmp[properties[i]];
         }
 
         // Keep a stack of the original error messages.
         if (error instanceof WrappedError) {
             this.error_stack = error.error_stack;
         } else {
             this.error_stack = [error];
         }
         this.error_stack.push(tmp);
 
         return this;
     };
 
     WrappedError.prototype = Object.create(Error.prototype, {});
 
     var reject = function(message, log) {
         // Creates a wrappable rsvp.Promise rejection function.
         // 
         // Creates a function that returns a rsvp.Promise.reject with a new WrappedError
         // that has the provided message and wraps the original error that 
         // caused the promise to reject.
         return function(error) { 
             var wrapped_error = new WrappedError(message, error);
             if (log) console.error(wrapped_error); 
             return rsvp.Promise.reject(wrapped_error); 
         };
     };
 
     var utils = {
         regex_split : regex_split,
         uuid : uuid,
         fixConsole : fixConsole,
         fixCarriageReturn : fixCarriageReturn,
         autoLinkUrls : autoLinkUrls,
         points_to_pixels : points_to_pixels,
         get_body_data : get_body_data,
         parse_url : parse_url,
         url_path_split : url_path_split,
         url_path_join : url_path_join,
         url_join_encode : url_join_encode,
         encode_uri_components : encode_uri_components,
         splitext : splitext,
         escape_html : escape_html,
         always_new : always_new,
         to_absolute_cursor_pos : to_absolute_cursor_pos,
         from_absolute_cursor_pos : from_absolute_cursor_pos,
         browser : browser,
         platform: platform,
         is_or_has : is_or_has,
         is_focused : is_focused,
         mergeopt: mergeopt,
         ajax_error_msg : ajax_error_msg,
         log_ajax_error : log_ajax_error,
         requireCodeMirrorMode : requireCodeMirrorMode,
         XHR_ERROR : XHR_ERROR,
         wrap_ajax_error : wrap_ajax_error,
         promising_ajax : promising_ajax,
         WrappedError: WrappedError,
         load_class: load_class,
         resolve_dict: resolve_dict,
         reject: reject,
     };
 
     // Backwards compatability.
     IPython.utils = utils;
     
     return utils;
 }); 

IPython/html/static/widgets/js/widget.js

@@ -1,611 +1,605
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define(["widgets/js/manager",
         "underscore",
         "backbone",
         "jquery",
         "base/js/utils",
         "base/js/namespace",
         "rsvp",
 ], function(widgetmanager, _, Backbone, $, utils, IPython, rsvp){
 
     var WidgetModel = Backbone.Model.extend({
         constructor: function (widget_manager, model_id, comm) {
             // Constructor
             //
             // Creates a WidgetModel instance.
             //
             // Parameters
             // ----------
             // widget_manager : WidgetManager instance
             // model_id : string
             //      An ID unique to this model.
             // comm : Comm instance (optional)
             this.widget_manager = widget_manager;
             this.state_change = rsvp.Promise.resolve();
             this._buffered_state_diff = {};
             this.pending_msgs = 0;
             this.msg_buffer = null;
             this.state_lock = null;
             this.id = model_id;
             this.views = {};
 
             if (comm !== undefined) {
                 // Remember comm associated with the model.
                 this.comm = comm;
                 comm.model = this;
 
                 // Hook comm messages up to model.
                 comm.on_close($.proxy(this._handle_comm_closed, this));
                 comm.on_msg($.proxy(this._handle_comm_msg, this));
             }
             return Backbone.Model.apply(this);
         },
 
         send: function (content, callbacks) {
             // Send a custom msg over the comm.
             if (this.comm !== undefined) {
                 var data = {method: 'custom', content: content};
                 this.comm.send(data, callbacks);
                 this.pending_msgs++;
             }
         },
 
         _handle_comm_closed: function (msg) {
             // Handle when a widget is closed.
             this.trigger('comm:close');
             this.stopListening();
             this.trigger('destroy', this);
             delete this.comm.model; // Delete ref so GC will collect widget model.
             delete this.comm;
             delete this.model_id; // Delete id from model so widget manager cleans up.
             for (var id in this.views) {
                 if (this.views.hasOwnProperty(id)) {
                     this.views[id].remove();
                 }
             }
         },
 
         _handle_comm_msg: function (msg) {
             // Handle incoming comm msg.
             var method = msg.content.data.method;
             var that = this;
             switch (method) {
                 case 'update':
                     this.state_change = this.state_change.then(function() {
                         return that.set_state(msg.content.data.state);
-                    }).catch(utils.reject({
-                        message: "Couldn't process update msg",
-                        model_id: that.id
-                    }, true));
+                    }).catch(utils.reject("Couldn't process update msg for model id '" + String(that.id) + "'", true));
                     break;
                 case 'custom':
                     this.trigger('msg:custom', msg.content.data.content);
                     break;
                 case 'display':
                     this.state_change = this.state_change.then(function () {
                         return that.widget_manager.display_view(msg, that);
-                    }).catch(utils.reject({
-                        message: "Couldn't process display msg",
-                        model_id: that.id
-                    }, true));
+                    }).catch(utils.reject("Couldn't process display msg for model id '" + String(that.id) + "'", true));
                     break;
             }
         },
 
         set_state: function (state) {
             var that = this;
             // Handle when a widget is updated via the python side.
             return this._unpack_models(state).then(function(state) {
                 that.state_lock = state;
                 try {
                     WidgetModel.__super__.set.call(that, state);
                 } finally {
                     that.state_lock = null;
                 }
             }, utils.reject("Couldn't set model state", true));
         },
 
         _handle_status: function (msg, callbacks) {
             // Handle status msgs.
 
             // execution_state : ('busy', 'idle', 'starting')
             if (this.comm !== undefined) {
                 if (msg.content.execution_state ==='idle') {
                     // Send buffer if this message caused another message to be
                     // throttled.
                     if (this.msg_buffer !== null &&
                         (this.get('msg_throttle') || 3) === this.pending_msgs) {
                         var data = {method: 'backbone', sync_method: 'update', sync_data: this.msg_buffer};
                         this.comm.send(data, callbacks);
                         this.msg_buffer = null;
                     } else {
                         --this.pending_msgs;
                     }
                 }
             }
         },
 
         callbacks: function(view) {
             // Create msg callbacks for a comm msg.
             var callbacks = this.widget_manager.callbacks(view);
 
             if (callbacks.iopub === undefined) {
                 callbacks.iopub = {};
             }
 
             var that = this;
             callbacks.iopub.status = function (msg) {
                 that._handle_status(msg, callbacks);
             };
             return callbacks;
         },
 
         set: function(key, val, options) {
             // Set a value.
             var return_value = WidgetModel.__super__.set.apply(this, arguments);
 
             // Backbone only remembers the diff of the most recent set()
             // operation.  Calling set multiple times in a row results in a 
             // loss of diff information.  Here we keep our own running diff.
             this._buffered_state_diff = $.extend(this._buffered_state_diff, this.changedAttributes() || {});
             return return_value;
         },
 
         sync: function (method, model, options) {
             // Handle sync to the back-end.  Called when a model.save() is called.
 
             // Make sure a comm exists.
             var error = options.error || function() {
                 console.error('Backbone sync error:', arguments);
             };
             if (this.comm === undefined) {
                 error();
                 return false;
             }
 
             // Delete any key value pairs that the back-end already knows about.
             var attrs = (method === 'patch') ? options.attrs : model.toJSON(options);
             if (this.state_lock !== null) {
                 var keys = Object.keys(this.state_lock);
                 for (var i=0; i<keys.length; i++) {
                     var key = keys[i];
                     if (attrs[key] === this.state_lock[key]) {
                         delete attrs[key];
                     }
                 }
             }
 
             // Only sync if there are attributes to send to the back-end.
             attrs = this._pack_models(attrs);
             if (_.size(attrs) > 0) {
 
                 // If this message was sent via backbone itself, it will not
                 // have any callbacks.  It's important that we create callbacks
                 // so we can listen for status messages, etc...
                 var callbacks = options.callbacks || this.callbacks();
 
                 // Check throttle.
                 if (this.pending_msgs >= (this.get('msg_throttle') || 3)) {
                     // The throttle has been exceeded, buffer the current msg so
                     // it can be sent once the kernel has finished processing 
                     // some of the existing messages.
                     
                     // Combine updates if it is a 'patch' sync, otherwise replace updates
                     switch (method) {
                         case 'patch':
                             this.msg_buffer = $.extend(this.msg_buffer || {}, attrs);
                             break;
                         case 'update':
                         case 'create':
                             this.msg_buffer = attrs;
                             break;
                         default:
                             error();
                             return false;
                     }
                     this.msg_buffer_callbacks = callbacks;
 
                 } else {
                     // We haven't exceeded the throttle, send the message like 
                     // normal.
                     var data = {method: 'backbone', sync_data: attrs};
                     this.comm.send(data, callbacks);
                     this.pending_msgs++;
                 }
             }
             // Since the comm is a one-way communication, assume the message 
             // arrived.  Don't call success since we don't have a model back from the server
             // this means we miss out on the 'sync' event.
             this._buffered_state_diff = {};
         },
 
         save_changes: function(callbacks) {
             // Push this model's state to the back-end
             //
             // This invokes a Backbone.Sync.
             this.save(this._buffered_state_diff, {patch: true, callbacks: callbacks});
         },
 
         _pack_models: function(value) {
             // Replace models with model ids recursively.
             var that = this;
             var packed;
             if (value instanceof Backbone.Model) {
                 return "IPY_MODEL_" + value.id;
 
             } else if ($.isArray(value)) {
                 packed = [];
                 _.each(value, function(sub_value, key) {
                     packed.push(that._pack_models(sub_value));
                 });
                 return packed;
             } else if (value instanceof Date || value instanceof String) {
                 return value;
             } else if (value instanceof Object) {
                 packed = {};
                 _.each(value, function(sub_value, key) {
                     packed[key] = that._pack_models(sub_value);
                 });
                 return packed;
 
             } else {
                 return value;
             }
         },
 
         _unpack_models: function(value) {
             // Replace model ids with models recursively.
             var that = this;
             var unpacked;
             if ($.isArray(value)) {
                 unpacked = [];
                 _.each(value, function(sub_value, key) {
                     unpacked.push(that._unpack_models(sub_value));
                 });
                 return rsvp.Promise.all(unpacked);
             } else if (value instanceof Object) {
                 unpacked = {};
                 _.each(value, function(sub_value, key) {
                     unpacked[key] = that._unpack_models(sub_value);
                 });
                 return utils.resolve_dict(unpacked);
             } else if (typeof value === 'string' && value.slice(0,10) === "IPY_MODEL_") {
                 // get_model returns a promise already
                 return this.widget_manager.get_model(value.slice(10, value.length));
             } else {
                 return rsvp.Promise.resolve(value);
             }
         },
 
         on_some_change: function(keys, callback, context) {
             // on_some_change(["key1", "key2"], foo, context) differs from
             // on("change:key1 change:key2", foo, context).
             // If the widget attributes key1 and key2 are both modified, 
             // the second form will result in foo being called twice
             // while the first will call foo only once.
             this.on('change', function() {
                 if (keys.some(this.hasChanged, this)) {
                     callback.apply(context);
                 }
             }, this);
 
        },
     });
     widgetmanager.WidgetManager.register_widget_model('WidgetModel', WidgetModel);
 
 
     var WidgetView = Backbone.View.extend({
         initialize: function(parameters) {
             // Public constructor.
             this.model.on('change',this.update,this);
             this.options = parameters.options;
             this.child_model_views = {};
             this.child_views = {};
             this.id = this.id || utils.uuid();
             this.model.views[this.id] = this;
             this.on('displayed', function() { 
                 this.is_displayed = true; 
             }, this);
         },
 
         update: function(){
             // Triggered on model change.
             //
             // Update view to be consistent with this.model
         },
 
         create_child_view: function(child_model, options) {
             // Create and promise that resolves to a child view of a given model
             var that = this;
             options = $.extend({ parent: this }, options || {});
             return this.model.widget_manager.create_view(child_model, options).then(function(child_view) {
                 // Associate the view id with the model id.
                 if (that.child_model_views[child_model.id] === undefined) {
                     that.child_model_views[child_model.id] = [];
                 }
                 that.child_model_views[child_model.id].push(child_view.id);
                 // Remember the view by id.
                 that.child_views[child_view.id] = child_view;
                 return child_view;
             }, utils.reject("Couldn't create child view"));
         },
 
         pop_child_view: function(child_model) {
             // Delete a child view that was previously created using create_child_view.
             var view_ids = this.child_model_views[child_model.id];
             if (view_ids !== undefined) {
 
                 // Only delete the first view in the list.
                 var view_id = view_ids[0];
                 var view = this.child_views[view_id];
                 delete this.child_views[view_id];
                 view_ids.splice(0,1);
                 delete child_model.views[view_id];
             
                 // Remove the view list specific to this model if it is empty.
                 if (view_ids.length === 0) {
                     delete this.child_model_views[child_model.id];
                 }
                 return view;
             }
             return null;
         },
 
         do_diff: function(old_list, new_list, removed_callback, added_callback) {
             // Difference a changed list and call remove and add callbacks for 
             // each removed and added item in the new list.
             //
             // Parameters
             // ----------
             // old_list : array
             // new_list : array
             // removed_callback : Callback(item)
             //      Callback that is called for each item removed.
             // added_callback : Callback(item)
             //      Callback that is called for each item added.
 
             // Walk the lists until an unequal entry is found.
             var i;
             for (i = 0; i < new_list.length; i++) {
                 if (i >= old_list.length || new_list[i] !== old_list[i]) {
                     break;
                 }
             }
 
             // Remove the non-matching items from the old list.
             for (var j = i; j < old_list.length; j++) {
                 removed_callback(old_list[j]);
             }
 
             // Add the rest of the new list items.
             for (; i < new_list.length; i++) {
                 added_callback(new_list[i]);
             }
         },
 
         callbacks: function(){
             // Create msg callbacks for a comm msg.
             return this.model.callbacks(this);
         },
 
         render: function(){
             // Render the view.
             //
             // By default, this is only called the first time the view is created
         },
 
         show: function(){
             // Show the widget-area
             if (this.options && this.options.cell &&
                 this.options.cell.widget_area !== undefined) {
                 this.options.cell.widget_area.show();
             }
         },
 
         send: function (content) {
             // Send a custom msg associated with this view.
             this.model.send(content, this.callbacks());
         },
 
         touch: function () {
             this.model.save_changes(this.callbacks());
         },
 
         after_displayed: function (callback, context) {
             // Calls the callback right away is the view is already displayed
             // otherwise, register the callback to the 'displayed' event.
             if (this.is_displayed) {
                 callback.apply(context);
             } else {
                 this.on('displayed', callback, context);
             }
         },
     });
 
 
     var DOMWidgetView = WidgetView.extend({
         initialize: function (parameters) {
             // Public constructor
             DOMWidgetView.__super__.initialize.apply(this, [parameters]);
             this.on('displayed', this.show, this);
             this.model.on('change:visible', this.update_visible, this);
             this.model.on('change:_css', this.update_css, this);
 
             this.model.on('change:_dom_classes', function(model, new_classes) {
                 var old_classes = model.previous('_dom_classes');
                 this.update_classes(old_classes, new_classes);
             }, this);
 
             this.model.on('change:color', function (model, value) { 
                 this.update_attr('color', value); }, this);
 
             this.model.on('change:background_color', function (model, value) { 
                 this.update_attr('background', value); }, this);
 
             this.model.on('change:width', function (model, value) { 
                 this.update_attr('width', value); }, this);
 
             this.model.on('change:height', function (model, value) { 
                 this.update_attr('height', value); }, this);
 
             this.model.on('change:border_color', function (model, value) { 
                 this.update_attr('border-color', value); }, this);
 
             this.model.on('change:border_width', function (model, value) { 
                 this.update_attr('border-width', value); }, this);
 
             this.model.on('change:border_style', function (model, value) { 
                 this.update_attr('border-style', value); }, this);
 
             this.model.on('change:font_style', function (model, value) { 
                 this.update_attr('font-style', value); }, this);
 
             this.model.on('change:font_weight', function (model, value) { 
                 this.update_attr('font-weight', value); }, this);
 
             this.model.on('change:font_size', function (model, value) { 
                 this.update_attr('font-size', this._default_px(value)); }, this);
 
             this.model.on('change:font_family', function (model, value) { 
                 this.update_attr('font-family', value); }, this);
 
             this.model.on('change:padding', function (model, value) { 
                 this.update_attr('padding', value); }, this);
 
             this.model.on('change:margin', function (model, value) { 
                 this.update_attr('margin', this._default_px(value)); }, this);
 
             this.model.on('change:border_radius', function (model, value) { 
                 this.update_attr('border-radius', this._default_px(value)); }, this);
 
             this.after_displayed(function() {
                 this.update_visible(this.model, this.model.get("visible"));
                 this.update_classes([], this.model.get('_dom_classes'));
                 
                 this.update_attr('color', this.model.get('color'));
                 this.update_attr('background', this.model.get('background_color'));
                 this.update_attr('width', this.model.get('width'));
                 this.update_attr('height', this.model.get('height'));
                 this.update_attr('border-color', this.model.get('border_color'));
                 this.update_attr('border-width', this.model.get('border_width'));
                 this.update_attr('border-style', this.model.get('border_style'));
                 this.update_attr('font-style', this.model.get('font_style'));
                 this.update_attr('font-weight', this.model.get('font_weight'));
                 this.update_attr('font-size', this.model.get('font_size'));
                 this.update_attr('font-family', this.model.get('font_family'));
                 this.update_attr('padding', this.model.get('padding'));
                 this.update_attr('margin', this.model.get('margin'));
                 this.update_attr('border-radius', this.model.get('border_radius'));
 
                 this.update_css(this.model, this.model.get("_css"));
             }, this);
         },
 
         _default_px: function(value) {
             // Makes browser interpret a numerical string as a pixel value.
             if (/^\d+\.?(\d+)?$/.test(value.trim())) {
                 return value.trim() + 'px';
             }
             return value;
         },
 
         update_attr: function(name, value) {
             // Set a css attr of the widget view.
             this.$el.css(name, value);
         },
 
         update_visible: function(model, value) {
             // Update visibility
             this.$el.toggle(value);
          },
 
         update_css: function (model, css) {
             // Update the css styling of this view.
             var e = this.$el;
             if (css === undefined) {return;}
             for (var i = 0; i < css.length; i++) {
                 // Apply the css traits to all elements that match the selector.
                 var selector = css[i][0];
                 var elements = this._get_selector_element(selector);
                 if (elements.length > 0) {
                     var trait_key = css[i][1];
                     var trait_value = css[i][2];
                     elements.css(trait_key ,trait_value);
                 }
             }
         },
 
         update_classes: function (old_classes, new_classes, $el) {
             // Update the DOM classes applied to an element, default to this.$el.
             if ($el===undefined) {
                 $el = this.$el;
             }
             this.do_diff(old_classes, new_classes, function(removed) {
                 $el.removeClass(removed);
             }, function(added) {
                 $el.addClass(added);
             });
         },
 
         update_mapped_classes: function(class_map, trait_name, previous_trait_value, $el) {
             // Update the DOM classes applied to the widget based on a single
             // trait's value.
             //
             // Given a trait value classes map, this function automatically
             // handles applying the appropriate classes to the widget element
             // and removing classes that are no longer valid.
             //
             // Parameters
             // ----------
             // class_map: dictionary
             //  Dictionary of trait values to class lists.
             //  Example:
             //      {
             //          success: ['alert', 'alert-success'],
             //          info: ['alert', 'alert-info'],
             //          warning: ['alert', 'alert-warning'],
             //          danger: ['alert', 'alert-danger']
             //      };
             // trait_name: string
             //  Name of the trait to check the value of.
             // previous_trait_value: optional string, default ''
             //  Last trait value
             // $el: optional jQuery element handle, defaults to this.$el
             //  Element that the classes are applied to.
             var key = previous_trait_value;
             if (key === undefined) {
                 key = this.model.previous(trait_name);
             }
             var old_classes = class_map[key] ? class_map[key] : [];
             key = this.model.get(trait_name);
             var new_classes = class_map[key] ? class_map[key] : [];
 
             this.update_classes(old_classes, new_classes, $el || this.$el);
         },
         
         _get_selector_element: function (selector) {
             // Get the elements via the css selector.
             var elements;
             if (!selector) {
                 elements = this.$el;
             } else {
                 elements = this.$el.find(selector).addBack(selector);
             }
             return elements;
         },
     });
 
     
     var widget = {
         'WidgetModel': WidgetModel,
         'WidgetView': WidgetView,
         'DOMWidgetView': DOMWidgetView,
     };
 
     // For backwards compatability.
     $.extend(IPython, widget);
 
     return widget;
 });