Add handling of failed publish.

When publishing, if the selected page does not yet have a page created,
handle the FailedPublishNothingToPublish error so that the user is not
presented with an exception. A warning is shown to the user that some
languages failed to publish due to nothing to publish and to check that
a page has been created for selected languages. Additionally fixed a
validation issue where publish would always succeed if all languages
were selected.

Issue: 15352

src/Umbraco.Web.BackOffice/Controllers/ContentController.cs

@@ -2061,7 +2061,7 @@ public IActionResult PostPublishByIdAndCulture(PublishContent model)
         var languageCount = _allLangs.Value.Count();
 
         // If there is no culture specified or the cultures specified are equal to the total amount of languages, publish the content in all cultures.
-        if (model.Cultures == null || !model.Cultures.Any() || model.Cultures.Length == languageCount)
+        if (model.Cultures == null || !model.Cultures.Any())
         {
             return PostPublishById(model.Id);
         }
@@ -2322,7 +2322,7 @@ public async Task<IActionResult> PostSort(ContentSortOrder sorted)
         }
 
         var languageCount = _allLangs.Value.Count();
-        if (model.Cultures?.Length == 0 || model.Cultures?.Length == languageCount)
+        if (model.Cultures?.Length == 0)
         {
             //this means that the entire content item will be unpublished
             PublishResult unpublishResult = _contentService.Unpublish(foundContent, userId: _backofficeSecurityAccessor.BackOfficeSecurity?.GetUserId().Result ?? -1);
@@ -2786,6 +2786,7 @@ private void AddMessageForPublishStatus(IReadOnlyCollection<PublishResult> statu
                 case PublishResultType.FailedPublishIsTrashed:
                 case PublishResultType.FailedPublishContentInvalid:
                 case PublishResultType.FailedPublishMandatoryCultureMissing:
+                case PublishResultType.FailedPublishNothingToPublish:
                     //the rest that we are looking for each belong in their own group
                     return x.Result;
                 default:
@@ -2928,6 +2929,11 @@ private void AddMessageForPublishStatus(IReadOnlyCollection<PublishResult> statu
                         _localizedTextService.Localize(null, "publish"),
                         "publish/contentPublishedFailedByCulture");
                     break;
+                case PublishResultType.FailedPublishNothingToPublish:
+                    display.AddWarningNotification(
+                         _localizedTextService.Localize(null, "publish"),
+                        $"Nothing to publish for some languages. Ensure selected languages have a page created.");
+                    break;
                 default:
                     throw new IndexOutOfRangeException($"PublishedResultType \"{status.Key}\" was not expected.");
             }