Fixed: Tag deletion via api if tag is still in use

src/NzbDrone.Core/Datastore/ModelConflictException.cs

@@ -0,0 +1,20 @@
+using System;
+using NzbDrone.Common.Exceptions;
+
+namespace NzbDrone.Core.Datastore
+{
+    public class ModelConflictException : NzbDroneException
+    {
+        public ModelConflictException(Type modelType, int modelId)
+            : base("{0} with ID {1} cannot be modified", modelType.Name, modelId)
+        {
+
+        }
+
+        public ModelConflictException(Type modelType, int modelId, string message)
+            : base("{0} with ID {1} {2}", modelType.Name, modelId, message)
+        {
+
+        }
+    }
+}

src/NzbDrone.Core/NzbDrone.Core.csproj

@@ -142,6 +142,7 @@
     <Compile Include="Datastore\Migration\130_episode_last_searched_time.cs" />
     <Compile Include="Datastore\Migration\129_add_relative_original_path_to_episode_file.cs" />
     <Compile Include="Datastore\Migration\128_rename_quality_profiles_add_upgrade_allowed.cs" />
+    <Compile Include="Datastore\ModelConflictException.cs" />
     <Compile Include="DecisionEngine\Specifications\AlreadyImportedSpecification.cs" />
     <Compile Include="CustomFilters\CustomFilter.cs" />
     <Compile Include="CustomFilters\CustomFilterRepository.cs" />

src/NzbDrone.Core/Tags/TagDetails.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using NzbDrone.Core.Datastore;
 
 namespace NzbDrone.Core.Tags
@@ -10,5 +11,13 @@ namespace NzbDrone.Core.Tags
         public List<int> NotificationIds { get; set; }
         public List<int> RestrictionIds { get; set; }
         public List<int> DelayProfileIds { get; set; }
+
+        public bool InUse
+        {
+            get
+            {
+                return (SeriesIds.Any() || NotificationIds.Any() || RestrictionIds.Any() || DelayProfileIds.Any());
+            }
+        }
     }
 }

src/NzbDrone.Core/Tags/TagService.cs

@@ -1,5 +1,7 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
+using NzbDrone.Core.Datastore;
 using NzbDrone.Core.Messaging.Events;
 using NzbDrone.Core.Notifications;
 using NzbDrone.Core.Profiles.Delay;
@@ -147,6 +149,12 @@ namespace NzbDrone.Core.Tags
 
         public void Delete(int tagId)
         {
+            var details = Details(tagId);
+            if (details.InUse)
+            {
+                throw new ModelConflictException(typeof(Tag), tagId, $"'{details.Label}' cannot be deleted since it's still in use");
+            }
+
             _repo.Delete(tagId);
             _eventAggregator.PublishEvent(new TagsUpdatedEvent());
         }

src/Sonarr.Http/ErrorManagement/SonarrErrorPipeline.cs

@@ -3,6 +3,7 @@ using System.Data.SQLite;
 using FluentValidation;
 using Nancy;
 using NLog;
+using NzbDrone.Core.Datastore;
 using NzbDrone.Core.Exceptions;
 using Sonarr.Http.Exceptions;
 using Sonarr.Http.Extensions;
@@ -23,26 +24,20 @@ namespace Sonarr.Http.ErrorManagement
         {
             _logger.Trace("Handling Exception");
 
-            var apiException = exception as ApiException;
-
-            if (apiException != null)
+            if (exception is ApiException apiException)
             {
                 _logger.Warn(apiException, "API Error");
                 return apiException.ToErrorResponse();
             }
             
-            var validationException = exception as ValidationException;
-
-            if (validationException != null)
+            if (exception is ValidationException validationException)
             {
                 _logger.Warn("Invalid request {0}", validationException.Message);
 
                 return validationException.Errors.AsResponse(HttpStatusCode.BadRequest);
             }
 
-            var clientException = exception as NzbDroneClientException;
-
-            if (clientException != null)
+            if (exception is NzbDroneClientException clientException)
             {
                 return new ErrorModel
                 {
@@ -51,9 +46,25 @@ namespace Sonarr.Http.ErrorManagement
                 }.AsResponse((HttpStatusCode)clientException.StatusCode);
             }
 
-            var sqLiteException = exception as SQLiteException;
+            if (exception is ModelNotFoundException notFoundException)
+            {
+                return new ErrorModel
+                {
+                    Message = exception.Message,
+                    Description = exception.ToString()
+                }.AsResponse(HttpStatusCode.NotFound);
+            }
+
+            if (exception is ModelConflictException conflictException)
+            {
+                return new ErrorModel
+                {
+                    Message = exception.Message,
+                    Description = exception.ToString()
+                }.AsResponse(HttpStatusCode.Conflict);
+            }
 
-            if (sqLiteException != null)
+            if (exception is SQLiteException sqLiteException)
             {
                 if (context.Request.Method == "PUT" || context.Request.Method == "POST")
                 {