reduced code duplication

Author: Kamil Zakiev

src/Scrutor/ServiceCollectionExtensions.Decoration.cs

@@ -245,7 +245,13 @@ private static IServiceCollection DecorateOpenGeneric(this IServiceCollection se
 
         private static IServiceCollection DecorateOpenGeneric(this IServiceCollection services, Type serviceType, Func<object, IServiceProvider, object> decorator)
         {
-            if (services.TryDecorateOpenGeneric(serviceType, decorator))
+            bool TryDecorate(Type[] typeArguments)
+            {
+                var closedServiceType = serviceType.MakeGenericType(typeArguments);
+                return services.TryDecorateDescriptors(closedServiceType, x => x.Decorate(decorator));
+            }
+
+            if (services.TryDecorateOpenGeneric(serviceType, openTypeDecorator: TryDecorate))
             {
                 return services;
             }
@@ -268,10 +274,12 @@ private static IServiceCollection DecorateOpenGeneric(this IServiceCollection se
             throw new MissingTypeRegistrationException(serviceType);
         }
 
-        private static bool TryDecorateOpenGeneric(this IServiceCollection services, Type serviceType, Type decoratorType)
+        private static bool TryDecorateOpenGeneric(this IServiceCollection services, Type serviceType, Type decoratorType = null, Func<Type[], bool> openTypeDecorator = null)
         {
             bool TryDecorate(Type[] typeArguments)
             {
+                Preconditions.NotNull(decoratorType, nameof(decoratorType));
+                
                 var closedServiceType = serviceType.MakeGenericType(typeArguments);
                 var closedDecoratorType = decoratorType.MakeGenericType(typeArguments);
 
@@ -288,28 +296,8 @@ bool TryDecorate(Type[] typeArguments)
                 return false;
             }
 
-            return arguments.Aggregate(true, (result, args) => result && TryDecorate(args));
-        }
-
-        private static bool TryDecorateOpenGeneric(this IServiceCollection services, Type serviceType, Func<object, IServiceProvider, object> decorator)
-        {
-            bool TryDecorate(Type[] typeArguments)
-            {
-                var closedServiceType = serviceType.MakeGenericType(typeArguments);
-                return services.TryDecorateDescriptors(closedServiceType, x => x.Decorate(decorator));
-            }
-
-            var arguments = services
-                .Where(descriptor => descriptor.ServiceType.IsAssignableTo(serviceType))
-                .Select(descriptor => descriptor.ServiceType.GenericTypeArguments)
-                .ToArray();
-
-            if (arguments.Length == 0)
-            {
-                return false;
-            }
-
-            return arguments.Aggregate(true, (result, args) => result && TryDecorate(args));
+            var tryDecorate = openTypeDecorator ?? TryDecorate;
+            return arguments.Aggregate(true, (result, args) => result && tryDecorate(args));
         }
 
         private static IServiceCollection DecorateDescriptors(this IServiceCollection services, Type serviceType, Func<ServiceDescriptor, ServiceDescriptor> decorator)