Wait for any promises returned by a view's render method before considering the view created

This lets a view wait on children views to be created before considering itself created.

Thanks to @ssunkara for catching this.

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

@@ -1,240 +1,239
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     "underscore",
     "backbone",
     "jquery",
     "base/js/utils",
     "base/js/namespace",
 ], function (_, Backbone, $, utils, IPython) {
     "use strict";
     //--------------------------------------------------------------------
     // WidgetManager class
     //--------------------------------------------------------------------
     var WidgetManager = function (comm_manager, notebook) {
         // Public constructor
         WidgetManager._managers.push(this);
 
         // Attach a comm manager to the 
         this.keyboard_manager = notebook.keyboard_manager;
         this.notebook = notebook;
         this.comm_manager = comm_manager;
         this._models = {}; /* Dictionary of model ids and model instances */
 
         // Register with the comm manager.
         this.comm_manager.register_target('ipython.widget', $.proxy(this._handle_comm_open, this));
     };
 
     //--------------------------------------------------------------------
     // Class level
     //--------------------------------------------------------------------
     WidgetManager._model_types = {}; /* Dictionary of model type names (target_name) and model types. */
     WidgetManager._view_types = {}; /* Dictionary of view names and view types. */
     WidgetManager._managers = []; /* List of widget managers */
 
     WidgetManager.register_widget_model = function (model_name, model_type) {
         // Registers a widget model by name.
         WidgetManager._model_types[model_name] = model_type;
     };
 
     WidgetManager.register_widget_view = function (view_name, view_type) {
         // Registers a widget view by name.
         WidgetManager._view_types[view_name] = view_type;
     };
 
     //--------------------------------------------------------------------
     // Instance level
     //--------------------------------------------------------------------
     WidgetManager.prototype.display_view = function(msg, model) {
         // Displays a view for a particular model.
         var that = this;
         var cell = this.get_msg_cell(msg.parent_header.msg_id);
         if (cell === null) {
             return Promise.reject(new Error("Could not determine where the display" +
                                             " message was from.  Widget will not be displayed"));
         } else if (cell.widget_subarea) {
             var dummy = $('<div />');
             cell.widget_subarea.append(dummy);
             return this.create_view(model, {cell: cell}).then(
                 function(view) {
                     that._handle_display_view(view);
                     dummy.replaceWith(view.$el);
                     view.trigger('displayed');
                     return view;
                 }).catch(utils.reject('Could not display view', true));
         }
     };
 
     WidgetManager.prototype._handle_display_view = function (view) {
         // Have the IPython keyboard manager disable its event
         // handling so the widget can capture keyboard input.
         // Note, this is only done on the outer most widgets.
         if (this.keyboard_manager) {
             this.keyboard_manager.register_events(view.$el);
         
             if (view.additional_elements) {
                 for (var i = 0; i < view.additional_elements.length; i++) {
                     this.keyboard_manager.register_events(view.additional_elements[i]);
                 }
             } 
         }
     };
     
     WidgetManager.prototype.create_view = function(model, options) {
         // Creates a promise for a view of a given model
 
         // Make sure the view creation is not out of order with 
         // any state updates.
         model.state_change = model.state_change.then(function() {
             
             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
                 // the cell for the view that is created.
                 options = options || {};
                 if (options.parent !== undefined) {
                     options.cell = options.parent.options.cell;
                 }
                 // Create and render the view...
                 var parameters = {model: model, options: options};
                 var view = new ViewType(parameters);
                 view.listenTo(model, 'destroy', view.remove);
-                view.render();
-                return view;
+                return Promise.resolve(view.render()).then(function() {return view;});
             }).catch(utils.reject("Couldn't create a view for model id '" + String(model.id) + "'", true));
         });
         return model.state_change;
     };
 
     WidgetManager.prototype.get_msg_cell = function (msg_id) {
         var cell = null;
         // First, check to see if the msg was triggered by cell execution.
         if (this.notebook) {
             cell = this.notebook.get_msg_cell(msg_id);
         }
         if (cell !== null) {
             return cell;
         }
         // Second, check to see if a get_cell callback was defined
         // for the message.  get_cell callbacks are registered for
         // widget messages, so this block is actually checking to see if the
         // message was triggered by a widget.
         var kernel = this.comm_manager.kernel;
         if (kernel) {
             var callbacks = kernel.get_callbacks_for_msg(msg_id);
             if (callbacks && callbacks.iopub &&
                 callbacks.iopub.get_cell !== undefined) {
                 return callbacks.iopub.get_cell();
             }
         }
         
         // Not triggered by a cell or widget (no get_cell callback 
         // exists).
         return null;
     };
 
     WidgetManager.prototype.callbacks = function (view) {
         // callback handlers specific a view
         var callbacks = {};
         if (view && view.options.cell) {
 
             // Try to get output handlers
             var cell = view.options.cell;
             var handle_output = null;
             var handle_clear_output = null;
             if (cell.output_area) {
                 handle_output = $.proxy(cell.output_area.handle_output, cell.output_area);
                 handle_clear_output = $.proxy(cell.output_area.handle_clear_output, cell.output_area);
             }
 
             // Create callback dictionary using what is known
             var that = this;
             callbacks = {
                 iopub : {
                     output : handle_output,
                     clear_output : handle_clear_output,
 
                     // Special function only registered by widget messages.
                     // Allows us to get the cell for a message so we know
                     // where to add widgets if the code requires it.
                     get_cell : function () {
                         return cell;
                     },
                 },
             };
         }
         return callbacks;
     };
 
     WidgetManager.prototype.get_model = function (model_id) {
         // Get a promise for a model by model id.
         return this._models[model_id];
     };
 
     WidgetManager.prototype._handle_comm_open = function (comm, msg) {
         // Handle when a comm is opened.
         return this.create_model({
             model_name: msg.content.data.model_name, 
             model_module: msg.content.data.model_module, 
             comm: comm}).catch(utils.reject("Couldn't create a model.", true));
     };
 
     WidgetManager.prototype.create_model = function (options) {
         // Create and return a promise for a new widget model
         //
         // Minimally, one must provide the model_name and widget_class
         // parameters to create a model from Javascript.
         //
         // Example
         // --------
         // JS:
         // IPython.notebook.kernel.widget_manager.create_model({
         //      model_name: 'WidgetModel', 
         //      widget_class: 'IPython.html.widgets.widget_int.IntSlider'})
         //      .then(function(model) { console.log('Create success!', model); },
         //      $.proxy(console.error, console));
         //
         // Parameters
         // ----------
         // options: dictionary
         //  Dictionary of options with the following contents:
         //      model_name: string
         //          Target name of the widget model to create.
         //      model_module: (optional) string
         //          Module name of the widget model to create.
         //      widget_class: (optional) string
         //          Target name of the widget in the back-end.
         //      comm: (optional) Comm
         
         // Create a comm if it wasn't provided.
         var comm = options.comm;
         if (!comm) {
             comm = this.comm_manager.new_comm('ipython.widget', {'widget_class': options.widget_class});
         }
 
         var that = this;
         var model_id = comm.comm_id;
         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];
                 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;
     };
 
     // Backwards compatibility.
     IPython.WidgetManager = WidgetManager;
 
     return {'WidgetManager': WidgetManager};
 });