Add a WrappedError class

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

@@ -606,7 +606,7 b' define(['
         });
     };
 
-    var load = function(class_name, module_name, registry) {
+    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 
@@ -618,8 +618,7 b' define(['
             if (module_name) {
                 require([module_name], function(module) {
                     if (module[class_name] === undefined) {
-                        console.error('Class '+class_name+' not found in module '+module_name)
-                        reject();
+                        reject(new Error('Class '+class_name+' not found in module '+module_name));
                     } else {
                         resolve(module[class_name]);
                     }
@@ -628,14 +627,18 b' define(['
                 if (registry && registry[class_name]) {
                     resolve(registry[class_name]);
                 } else {
-                    console.error('Class '+class_name+' not found in registry ', registry);
-                    reject();
+                    reject(new Error({
+                        message: 'Class '+class_name+' not found in registry ', 
+                        registry: registry
+                    }));
                 }
             }
         });
     };
 
     var resolve_dict = function(d) {
+        // Resolve a promiseful dictionary.
+        // Returns a single Promise.
         var keys = Object.keys(d);
         var values = [];
         keys.forEach(function(key) {
@@ -650,6 +653,46 b' define(['
         });
     };
 
+    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 Promise rejection function.
+        // 
+        // Creates a function that returns a 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 Promise.reject(wrapped_error); 
+        };
+    };
+
     var utils = {
         regex_split : regex_split,
         uuid : uuid,
@@ -679,8 +722,10 b' define(['
         XHR_ERROR : XHR_ERROR,
         wrap_ajax_error : wrap_ajax_error,
         promising_ajax : promising_ajax,
-        load: load,
+        load_class: load_class,
         resolve_dict: resolve_dict,
+        WrappedError: WrappedError,
+        reject: reject,
     };
 
     // Backwards compatability.

IPython/html/static/services/kernels/comm.js

@@ -67,18 +67,21 b' define(['
         var content = msg.content;
         var that = this;
         
-        utils.load_class(content.target_name, content.target_module, this.targets)
-        .then(function(target) {
+        return utils.load_class(content.target_name, content.target_module, 
+            this.targets).then(function(target) {
+
             var comm = new Comm(content.target_name, content.comm_id);
             that.register_comm(comm);
             try {
                 target(comm, msg);
             } catch (e) {
-                console.log("Exception opening new comm:", e, e.stack, msg);
                 comm.close();
                 that.unregister_comm(comm);
+                var error = new utils.WrappedError("Exception opening new comm", e);
+                return Promise.reject(error);
             }
-        }, $.proxy(console.error, console));
+            return comm;
+        }, utils.reject('Could not open comm', true));
     };
     
     CommManager.prototype.comm_close = function (msg) {

IPython/html/static/widgets/js/manager.js

@@ -48,26 +48,33 b' define(['
     //--------------------------------------------------------------------
     WidgetManager.prototype.display_view = function(msg, model) {
         // Displays a view for a particular model.
-        var cell = this.get_msg_cell(msg.parent_header.msg_id);
-        if (cell === null) {
-            console.log("Could not determine where the display" + 
-                " message was from.  Widget will not be displayed");
-        } else {
-            var dummy = null;
-            if (cell.widget_subarea) {
-                dummy = $('<div />');
-                cell.widget_subarea.append(dummy);
+        return new Promise(function(resolve, reject) {
+            var cell = this.get_msg_cell(msg.parent_header.msg_id);
+            if (cell === null) {
+                reject(new Error("Could not determine where the display" + 
+                    " message was from.  Widget will not be displayed"));
+            } else {
+                var dummy = null;
+                if (cell.widget_subarea) {
+                    dummy = $('<div />');
+                    cell.widget_subarea.append(dummy);
+                }
+
+                var that = this;
+                this.create_view(model, {cell: cell}).then(function(view) {
+                    that._handle_display_view(view);
+                    if (dummy) {
+                        dummy.replaceWith(view.$el);
+                    }
+                    view.trigger('displayed');
+                    resolve(view);
+                }, function(error) { 
+                    reject(new utils.WrappedError('Could not display view', error)); 
+                });
             }
+        });
 
-            var that = this;
-            this.create_view(model, {cell: cell}).then(function(view) {
-                that._handle_display_view(view);
-                if (dummy) {
-                    dummy.replaceWith(view.$el);
-                }
-                view.trigger('displayed');
-            });
-        }
+        
     };
 
     WidgetManager.prototype._handle_display_view = function (view) {
@@ -79,7 +86,7 b' define(['
         
             if (view.additional_elements) {
                 for (var i = 0; i < view.additional_elements.length; i++) {
-                        this.keyboard_manager.register_events(view.additional_elements[i]);
+                    this.keyboard_manager.register_events(view.additional_elements[i]);
                 }
             } 
         }
@@ -87,7 +94,7 b' define(['
     
     WidgetManager.prototype.create_view = function(model, options) {
         // Creates a promise for a view of a given model
-        return utils.load(model.get('_view_name'), model.get('_view_module'),
+        return utils.load_class(model.get('_view_name'), model.get('_view_module'),
             WidgetManager._view_types).then(function(ViewType) {
 
                 // If a view is passed into the method, use that view's cell as
@@ -102,10 +109,7 b' define(['
                 view.listenTo(model, 'destroy', view.remove);
                 view.render();
                 return view;
-            }, function(error) {
-                console.error(error);
-                return Promise.reject(error);
-            });
+            }, utils.reject("Couldn't create a view for model id '" + String(model.id) + "'"));
     };
 
     WidgetManager.prototype.get_msg_cell = function (msg_id) {
@@ -177,7 +181,7 b' define(['
         this.create_model({
             model_name: msg.content.data.model_name, 
             model_module: msg.content.data.model_module, 
-            comm: comm});
+            comm: comm}).handle($.proxy(console.error, error));
     };
 
     WidgetManager.prototype.create_model = function (options) {
@@ -215,17 +219,18 b' define(['
 
         var that = this;
         var model_id = comm.comm_id;
-        var model_promise =  utils.load(options.model_name, options.model_module, WidgetManager._model_types)
+        var model_promise =  utils.load_class(options.model_name, options.model_module, WidgetManager._model_types)
             .then(function(ModelType) {
                 var widget_model = new ModelType(that, model_id, comm);
                 widget_model.once('comm:close', function () {
                     delete that._models[model_id];
                 });
                 return widget_model;
+
             }, function(error) {
                 delete that._models[model_id];
-                console.error(error);
-                return Promise.reject(error);
+                var wrapped_error = new utils.WrappedError("Couldn't create model", error);
+                return Promise.reject(wrapped_error);
             });
         this._models[model_id] = model_promise;
         return model_promise;

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

@@ -322,7 +322,7 b' define(["widgets/js/manager",'
                 // 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) {

IPython/html/static/widgets/js/widget_box.js

@@ -4,8 +4,9 b''
 define([
     "widgets/js/widget",
     "jqueryui",
+    "base/js/utils",
     "bootstrap",
-], function(widget, $){
+], function(widget, $, utils){
 
     var BoxView = widget.DOMWidgetView.extend({
         initialize: function(){
@@ -84,7 +85,7 b' define(['
                 that.after_displayed(function() {
                     view.trigger('displayed');
                 });
-            });
+            }, utils.reject("Couldn't add child view to box", true));
         },
     });