added service registration policies

#82

Author: JonasSamuelsson

src/Maestro/src/Configuration/IServiceRegistrationPolicy.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace Maestro.Configuration
+{
+	public interface IServiceRegistrationPolicy
+	{
+		void Register(Type type, IContainerBuilder builder);
+	}
+}

src/Maestro/src/Configuration/ScannerExtensions.cs

@@ -85,5 +85,10 @@ public static IScanner RegisterDefaultImplementations(this IScanner scanner, Act
 		{
 			return scanner.Using(new DefaultImplementationsConvention(action ?? (x => x.Add())));
 		}
+
+		public static IScanner UsingRegistrationPolicies(this IScanner scanner)
+		{
+			return scanner.Using<RegistrationPolicyConvention>();
+		}
 	}
 }

src/Maestro/src/Configuration/ServiceRegistrationPolicyAttribute.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace Maestro.Configuration
+{
+	[AttributeUsage(AttributeTargets.Class)]
+	public class ServiceRegistrationPolicyAttribute : Attribute
+	{
+		public Type PolicyType { get; }
+
+		public ServiceRegistrationPolicyAttribute(Type policyType)
+		{
+			PolicyType = policyType;
+		}
+	}
+}

src/Maestro/src/Conventions/ServiceRegistrationPolicyConvention.cs

@@ -0,0 +1,20 @@
+using Maestro.Configuration;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+
+namespace Maestro.Conventions
+{
+	internal class ServiceRegistrationPolicyConvention : IConvention
+	{
+		public void Process(IEnumerable<Type> types, IContainerBuilder builder)
+		{
+			types.ForEach(type => type
+				.GetCustomAttributes<ServiceRegistrationPolicyAttribute>(true)
+				.Select(x => (IServiceRegistrationPolicy)Activator.CreateInstance(x.PolicyType))
+				.ForEach(x => x.Register(type, builder))
+			);
+		}
+	}
+}

src/Maestro/test/Conventions/RegistrationPolicyTests.cs

@@ -0,0 +1,41 @@
+using Maestro.Configuration;
+using Shouldly;
+using System;
+using System.Linq;
+using System.Reflection;
+using Xunit;
+
+namespace Maestro.Tests.Conventions
+{
+	public class RegistrationPolicyTests
+	{
+		[Fact]
+		public void ShouldRegisterServiceUsingPolicy()
+		{
+			var container = new Container(x => x.Scan(s =>
+			{
+				var types = GetType().GetNestedTypes(BindingFlags.NonPublic);
+				s.Types(types).UsingRegistrationPolicies();
+			}));
+
+			var service1 = container.GetService<IFoo>();
+			var service2 = container.GetService<IFoo>();
+
+			service1.ShouldBeOfType<Foo>();
+			service1.ShouldBe(service2);
+		}
+
+		private interface IFoo { }
+
+		[ServiceRegistrationPolicy(typeof(CustomPolicy))]
+		private class Foo : IFoo { }
+
+		private class CustomPolicy : IServiceRegistrationPolicy
+		{
+			public void Register(Type type, IContainerBuilder builder)
+			{
+				builder.Add(type.GetInterfaces().Single()).Type(type).Singleton();
+			}
+		}
+	}
+}