Skip duplicate import list exclusions

(cherry picked from commit 9af2f137f41867a29d544fad77551672a79f24b6)

Closes #5003

src/Lidarr.Api.V1/ImportLists/ImportListExclusionController.cs

@@ -20,7 +20,11 @@ namespace Lidarr.Api.V1.ImportLists
         {
             _importListExclusionService = importListExclusionService;
 
-            SharedValidator.RuleFor(c => c.ForeignId).NotEmpty().SetValidator(guidValidator).SetValidator(importListExclusionExistsValidator);
+            SharedValidator.RuleFor(c => c.ForeignId).Cascade(CascadeMode.Stop)
+                .NotEmpty()
+                .SetValidator(guidValidator)
+                .SetValidator(importListExclusionExistsValidator);
+
             SharedValidator.RuleFor(c => c.ArtistName).NotEmpty();
         }
 

src/Lidarr.Api.V1/ImportLists/ImportListExclusionExistsValidator.cs

@@ -1,6 +1,7 @@
 using FluentValidation.Validators;
+using NzbDrone.Core.ImportLists.Exclusions;
 
-namespace NzbDrone.Core.ImportLists.Exclusions
+namespace Lidarr.Api.V1.ImportLists
 {
     public class ImportListExclusionExistsValidator : PropertyValidator
     {
@@ -20,7 +21,12 @@ namespace NzbDrone.Core.ImportLists.Exclusions
                 return true;
             }
 
-            return !_importListExclusionService.All().Exists(s => s.ForeignId == context.PropertyValue.ToString());
+            if (context.InstanceToValidate is not ImportListExclusionResource listExclusionResource)
+            {
+                return true;
+            }
+
+            return !_importListExclusionService.All().Exists(v => v.ForeignId == context.PropertyValue.ToString() && v.Id != listExclusionResource.Id);
         }
     }
 }

src/NzbDrone.Core/Validation/GuidValidator.cs

@@ -14,7 +14,7 @@ namespace NzbDrone.Core.Validation
                 return false;
             }
 
-            return Guid.TryParse(context.PropertyValue.ToString(), out var guidOutput);
+            return Guid.TryParse(context.PropertyValue.ToString(), out _);
         }
     }
 }