Put callbacks for create_view and create_child_view in options

And add errback support

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

@@ -95,6 +95,11 b' define(['
 
     WidgetManager.prototype.create_view = function(model, options, view) {
         // Creates a view for a particular model.
+        
+        var view_name = model.get('_view_name');
+        var view_mod = model.get('_view_module');
+        errback = options.errback || function(err) {console.log(err)};
+
         var instantiate_view = function(ViewType) {
             if (ViewType) {
                 // If a view is passed into the method, use that view's cell as
@@ -110,15 +115,16 b' define(['
                 view.render();
                 model.on('destroy', view.remove, view);
                 options.callback(view);
+            } else {
+                errback({unknown_view: true, view_name: view_name,
+                         view_module: view_mod})
             }
         }
-        
-        var view_name = model.get('_view_name');
-        var view_mod = model.get('_view_module');
+
         if (view_mod) {
             require([view_mod], function(module) {
                 instantiate_view(module[view_name])
-            });
+            }, errback);
         } else {
             instantiate_view(WidgetManager._view_types[view_name]);
         }

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

@@ -308,7 +308,7 b' define(["widgets/js/manager",'
             // Update view to be consistent with this.model
         },
 
-        create_child_view: function(child_model, callback, options) {
+        create_child_view: function(child_model, options) {
             // Create and return a child view.
             //
             // -given a model and (optionally) a view name if the view name is 
@@ -318,6 +318,7 b' define(["widgets/js/manager",'
             // it would be great to have the widget manager add the cell metadata
             // to the subview without having to add it here.
             var that = this;
+            var old_callback = options.callback || function(view) {};
             options = $.extend({ parent: this, callback: function(child_view) {
                 // Associate the view id with the model id.
                 if (that.child_model_views[child_model.id] === undefined) {
@@ -327,7 +328,7 b' define(["widgets/js/manager",'
 
                 // Remember the view by id.
                 that.child_views[child_view.id] = child_view;
-                callback(child_view);
+                old_callback(child_view);
              }}, options || {});
             
             this.model.widget_manager.create_view(child_model, options, this);

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

@@ -75,14 +75,14 b' define(['
         add_child_model: function(model) {
             // Called when a model is added to the children list.
             var that = this;
-            this.create_child_view(model, function(view) {
+            this.create_child_view(model, {callback: function(view) {
                 that.$box.append(view.$el);
 
                 // Trigger the displayed event of the child view.
                 that.after_displayed(function() {
                     view.trigger('displayed');
                 });
-            });
+            }});
         },
     });
 

IPython/html/static/widgets/js/widget_selectioncontainer.js

@@ -114,7 +114,7 b' define(['
             accordion_group.container_index = container_index;
             this.model_containers[model.id] = accordion_group;
             
-            this.create_child_view(model, function(view) {
+            this.create_child_view(model, {callback: function(view) {
                 accordion_inner.append(view.$el);
 
                 that.update();
@@ -124,7 +124,7 b' define(['
                 that.after_displayed(function() {
                     view.trigger('displayed');
                 });
-            });
+            }});
         },
     });
     
@@ -186,7 +186,7 b' define(['
                 .css('list-style-type', 'none')
                 .appendTo(this.$tabs);
             
-            this.create_child_view(model, function(view) {
+            this.create_child_view(model, {callback: function(view) {
                 view.parent_tab = tab;
 
                 var tab_text = $('<a />')
@@ -215,7 +215,7 b' define(['
                 that.after_displayed(function() {
                     view.trigger('displayed');
                 });
-            });
+            }});
         },
 
         update: function(options) {