Clean up promises code some more.

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

@@ -70,23 +70,21 b' define(['
 
         this.comms[comm_id] = utils.load_class(content.target_name, content.target_module, 
             this.targets).then(function(target) {
-
-            var comm = new Comm(content.target_name, comm_id);
-            comm.kernel = that.kernel;
-            try {
-                var response = target(comm, msg);
-                if (response instanceof Promise) {
-                    return response.then(function() { return Promise.resolve(comm); });
+                var comm = new Comm(content.target_name, comm_id);
+                comm.kernel = that.kernel;
+                try {
+                    var response = target(comm, msg);
+                } catch (e) {
+                    comm.close();
+                    that.unregister_comm(comm);
+                    var wrapped_error = new utils.WrappedError("Exception opening new comm", e);
+                    console.error(wrapped_error);
+                    return Promise.reject(wrapped_error);
                 }
-            } catch (e) {
-                comm.close();
-                that.unregister_comm(comm);
-                var wrapped_error = new utils.WrappedError("Exception opening new comm", e);
-                console.error(wrapped_error);
-                return Promise.reject(wrapped_error);
-            }
-            return Promise.resolve(comm);
-        }, utils.reject('Could not open comm', true));
+                // Regardless of the target return value, we need to
+                // then return the comm
+                return Promise.resolve(response).then(function() {return comm;});
+            }, utils.reject('Could not open comm', true));
         return this.comms[comm_id];
     };
     
@@ -104,6 +102,8 b' define(['
             } catch (e) {
                 console.log("Exception closing comm: ", e, e.stack, msg);
             }
+            // don't return a comm, so that further .then() functions
+            // get an undefined comm input
         });
     };
     
@@ -120,7 +120,7 b' define(['
             } catch (e) {
                 console.log("Exception handling comm msg: ", e, e.stack, msg);
             }
-            return Promise.resolve(comm);
+            return comm;
         });
     };
     

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

@@ -49,24 +49,24 b' define(['
     WidgetManager.prototype.display_view = function(msg, model) {
         // Displays a view for a particular model.
         var that = this;
-        return new Promise(function(resolve, reject) {
-            var cell = that.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 if (cell.widget_subarea) {
-                var dummy = $('<div />');
-                cell.widget_subarea.append(dummy);
-                that.create_view(model, {cell: cell}).then(function(view) {
+        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');
-                    resolve(view);
-                }, function(error) { 
-                    reject(new utils.WrappedError('Could not display view', error)); 
+                    return view;
+                },
+                function(error) {
+                    return Promise.reject(new utils.WrappedError('Could not display view', error));
                 });
-            }
-        });
+        }
     };
 
     WidgetManager.prototype._handle_display_view = function (view) {

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

@@ -95,7 +95,6 b' define(["widgets/js/manager",'
                 } finally {
                     that.state_lock = null;
                 }
-                return Promise.resolve();
             }, utils.reject("Couldn't set model state", true));
         },