Fix EnableEnumMappingValidation with non-enum configurations (#19)

* Add failing EnumMappingValidation test
* Add EnumMappingValidationRuntimeFeatureProxy to fix the bug

Author: trejjam

src/AutoMapper.Extensions.EnumMapping.Tests/EnumMappingValidation.cs

@@ -0,0 +1,15 @@
+using AutoMapper.Extensions.EnumMapping.Tests.Internal;
+
+namespace AutoMapper.Extensions.EnumMapping.Tests;
+
+public class EnumMappingValidation
+{
+    public class Default : AutoMapperSpecBase
+    {
+        protected override MapperConfiguration Configuration { get; } = new(cfg =>
+        {
+            cfg.EnableEnumMappingValidation();
+            cfg.CreateMap<object, object>();
+        });
+    }
+}

src/AutoMapper.Extensions.EnumMapping/EnumMapperConfigurationExpressionExtensions.cs

@@ -1,5 +1,4 @@
-using System.Linq;
-using AutoMapper.Extensions.EnumMapping.Internal;
+using AutoMapper.Extensions.EnumMapping.Internal;
 using AutoMapper.Internal;
 
 namespace AutoMapper.Extensions.EnumMapping
@@ -17,16 +16,9 @@ public static void EnableEnumMappingValidation(this IMapperConfigurationExpressi
         {
             mapperConfigurationExpression.Internal().Validator(context =>
             {
-                if (context.TypeMap != null)
-                {
-                    foreach (var feature in context.TypeMap.Features)
-                    {
-                        if (feature is IEnumMappingValidationRuntimeFeature validator)
-                        {
-                            validator.Validate(context.TypeMap.Types);
-                        }
-                    }
-                }
+                var validator = context.TypeMap?.Features.Get<EnumMappingValidationRuntimeFeatureProxy>();
+
+                validator?.Validate(context.TypeMap.Types);
             });
         }
     }

src/AutoMapper.Extensions.EnumMapping/Internal/EnumMappingFeature.cs

@@ -31,7 +31,9 @@ public void Configure(TypeMap typeMap)
 
             var lambdaExpression = new CustomMapExpressionFactory<TSource, TDestination>(enumValueMappings).Create();
             typeMap.TypeConverter = new ExpressionTypeConverter(lambdaExpression);
-            typeMap.Features.Set(new EnumMappingValidationRuntimeFeature<TSource, TDestination>(enumValueMappings, EnumMappingType));
+            typeMap.Features.Set(new EnumMappingValidationRuntimeFeatureProxy(
+                new EnumMappingValidationRuntimeFeature<TSource, TDestination>(enumValueMappings, EnumMappingType)
+            ));
         }
 
         private Dictionary<TSource, TDestination> CreateOverridedEnumValueMappings(Type sourceType, Type destinationType)

src/AutoMapper.Extensions.EnumMapping/Internal/EnumMappingValidationRuntimeFeatureProxy.cs

@@ -0,0 +1,17 @@
+using AutoMapper.Internal;
+
+namespace AutoMapper.Extensions.EnumMapping.Internal;
+
+internal class EnumMappingValidationRuntimeFeatureProxy : IEnumMappingValidationRuntimeFeature
+{
+    private readonly IEnumMappingValidationRuntimeFeature _innerValidationRuntimeFeature;
+
+    public EnumMappingValidationRuntimeFeatureProxy(IEnumMappingValidationRuntimeFeature innerValidationRuntimeFeature)
+    {
+        _innerValidationRuntimeFeature = innerValidationRuntimeFeature;
+    }
+
+    public void Seal(IGlobalConfiguration configurationProvider) => _innerValidationRuntimeFeature.Seal(configurationProvider);
+
+    public void Validate(TypePair typePair) => _innerValidationRuntimeFeature.Validate(typePair);
+}