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

src/Lidarr.Http/ErrorManagement/LidarrErrorPipeline.cs

@@ -24,26 +24,20 @@ namespace Lidarr.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(context);
             }
 
-            var validationException = exception as ValidationException;
-
-            if (validationException != null)
+            if (exception is ValidationException validationException)
             {
                 _logger.Warn("Invalid request {0}", validationException.Message);
 
                 return validationException.Errors.AsResponse(context, HttpStatusCode.BadRequest);
             }
 
-            var clientException = exception as NzbDroneClientException;
-
-            if (clientException != null)
+            if (exception is NzbDroneClientException clientException)
             {
                 return new ErrorModel
                 {
@@ -52,9 +46,25 @@ namespace Lidarr.Http.ErrorManagement
                 }.AsResponse(context, (HttpStatusCode)clientException.StatusCode);
             }
 
-            var sqLiteException = exception as SQLiteException;
+            if (exception is ModelNotFoundException notFoundException)
+            {
+                return new ErrorModel
+                {
+                    Message = exception.Message,
+                    Description = exception.ToString()
+                }.AsResponse(context, HttpStatusCode.NotFound);
+            }
+
+            if (exception is ModelConflictException conflictException)
+            {
+                return new ErrorModel
+                {
+                    Message = exception.Message,
+                    Description = exception.ToString()
+                }.AsResponse(context, HttpStatusCode.Conflict);
+            }
 
-            if (sqLiteException != null)
+            if (exception is SQLiteException sqLiteException)
             {
                 if (context.Request.Method == "PUT" || context.Request.Method == "POST")
                 {

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/Tags/TagDetails.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using NzbDrone.Core.Datastore;
 
 namespace NzbDrone.Core.Tags
@@ -11,5 +12,13 @@ namespace NzbDrone.Core.Tags
         public List<int> RestrictionIds { get; set; }
         public List<int> DelayProfileIds { get; set; }
         public List<int> ImportListIds { get; set; }
+
+        public bool InUse
+        {
+            get
+            {
+                return (ArtistIds.Any() || NotificationIds.Any() || RestrictionIds.Any() || DelayProfileIds.Any() || ImportListIds.Any());
+            }
+        }
     }
 }

src/NzbDrone.Core/Tags/TagService.cs

@@ -1,6 +1,8 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using NzbDrone.Core.ImportLists;
+using NzbDrone.Core.Datastore;
 using NzbDrone.Core.Messaging.Events;
 using NzbDrone.Core.Notifications;
 using NzbDrone.Core.Profiles.Delay;
@@ -149,6 +151,12 @@ 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());
         }