Handles trying to create a package with a duplicate name

src/Umbraco.Core/Packaging/PackageBuilder.cs

@@ -87,6 +87,11 @@ namespace Umbraco.Core.Packaging
 
             if (definition.Id == default)
             {
+                //check if the name already exists
+                var existsByName = packagesXml.Root.Elements("package").Any(x => x.AttributeValue<string>("name") == definition.Name);
+                if (existsByName)
+                    return false;
+
                 //need to gen an id and persist
                 // Find max id
                 var maxId = packagesXml.Root.Elements("package").Max(x => x.AttributeValue<int?>("id")) ?? 0;

src/Umbraco.Web.UI.Client/src/common/services/formhelper.service.js

@@ -110,7 +110,7 @@ function formHelper(angularHelper, serverValidationManager, notificationsService
             //Or, some strange server error
             if (err.status === 400) {
                 //now we need to look through all the validation errors
-                if (err.data && (err.data.ModelState)) {
+                if (err.data && err.data.ModelState) {
 
                     //wire up the server validation errs
                     this.handleServerValidation(err.data.ModelState);
@@ -118,11 +118,11 @@ function formHelper(angularHelper, serverValidationManager, notificationsService
                     //execute all server validation events and subscribers
                     serverValidationManager.notifyAndClearAllSubscriptions();                    
                 }
-                else {
+            }
+            else {
 
-                    //TODO: All YSOD handling should be done with an interceptor
-                    overlayService.ysod(err);
-                }
+                //TODO: All YSOD handling should be done with an interceptor
+                overlayService.ysod(err);
             }
             
         },

src/Umbraco.Web/Editors/PackageController.cs

@@ -57,7 +57,11 @@ namespace Umbraco.Web.Editors
 
             //save it
             if (!Services.PackagingService.SavePackage(model))
-                throw new HttpResponseException(Request.CreateNotificationValidationErrorResponse("The package with id {definition.Id} was not found"));
+                throw new HttpResponseException(
+                    Request.CreateNotificationValidationErrorResponse(
+                        model.Id == default
+                            ? $"A package with the name {model.Name} already exists"
+                            : $"The package with id {model.Id} was not found"));
 
             Services.PackagingService.ExportPackage(model);