Simplify include base with IncludeAllDerived

docs/Mapping-inheritance.md

@@ -27,6 +27,15 @@ CreateMap<DerivedEntity, DerivedDto>()
 
 In each case above, the derived mapping inherits the custom mapping configuration from the base mapping configuration.
 
+To include all derived maps, from the base type map configuration:
+
+```c#
+CreateMap<BaseEntity, BaseDto>()
+    .IncludeAllDerived();
+
+CreateMap<DerivedEntity, DerivedDto>();
+```
+
 ### Runtime polymorphism
 
 Take:

src/AutoMapper/Configuration/MappingExpression.cs

@@ -81,6 +81,8 @@ public IMappingExpression ForMember(string name, Action<IMemberConfigurationExpr
 
         public new IMappingExpression PreserveReferences() => (IMappingExpression)base.PreserveReferences();
 
+        public new IMappingExpression IncludeAllDerived() => (IMappingExpression) base.IncludeAllDerived();
+
         protected override IPropertyMapConfiguration CreateMemberConfigurationExpression<TMember>(MemberInfo member, Type sourceType)
             => new MemberConfigurationExpression(member, sourceType);
 
@@ -532,6 +534,12 @@ public IMappingExpression<TSource, TDestination> ValidateMemberList(MemberList m
             });
             return this;
         }
+
+        public IMappingExpression<TSource, TDestination> IncludeAllDerived()
+        {
+            TypeMapActions.Add(tm => tm.IncludeAllDerivedTypes = true);
+            return this;
+        }
 
         private IPropertyMapConfiguration GetDestinationMemberConfiguration(MemberInfo destinationMember) =>
             _memberConfigurations.FirstOrDefault(m => m.DestinationMember == destinationMember);

src/AutoMapper/IMappingExpression.cs

@@ -177,6 +177,12 @@ IMappingExpression AfterMap<TMappingAction>()
         /// <param name="memberList">Member list to validate</param>
         /// <returns>Itself</returns>
         IMappingExpression ValidateMemberList(MemberList memberList);
+
+        /// <summary>
+        /// Include this configuration in all derived types' maps. Works by scanning all type maps for matches during configuration.
+        /// </summary>
+        /// <returns>Itself</returns>
+        IMappingExpression IncludeAllDerived();
     }
 
     /// <summary>
@@ -444,5 +450,10 @@ IMappingExpression<TSource, TDestination> ForSourceMember(string sourceMemberNam
         /// <returns>Itself</returns>
         IMappingExpression<TSource, TDestination> ValidateMemberList(MemberList memberList);
 
+        /// <summary>
+        /// Include this configuration in all derived types' maps. Works by scanning all type maps for matches during configuration.
+        /// </summary>
+        /// <returns>Itself</returns>
+        IMappingExpression<TSource, TDestination> IncludeAllDerived();
     }
 }

src/AutoMapper/MapperConfiguration.cs

@@ -327,6 +327,19 @@ private void Seal()
                 profile.Register(this);
             }
 
+            foreach (var typeMap in _typeMapRegistry.Values.Where(tm => tm.IncludeAllDerivedTypes))
+            {
+                foreach (var derivedMap in _typeMapRegistry
+                    .Where(tm =>
+                        typeMap.SourceType.IsAssignableFrom(tm.Key.SourceType) &&
+                        typeMap.DestinationType.IsAssignableFrom(tm.Key.DestinationType) &&
+                        typeMap != tm.Value)
+                    .Select(tm => tm.Value))
+                {
+                    typeMap.IncludeDerivedTypes(derivedMap.SourceType, derivedMap.DestinationType);
+                }
+            }
+
             foreach (var profile in Profiles)
             {
                 profile.Configure(this);

src/AutoMapper/TypeMap.cs

@@ -77,6 +77,8 @@ public PathMap FindPathMapByDestinationPath(string destinationFullPath) =>
 
         public bool ConstructDestinationUsingServiceLocator { get; set; }
 
+        public bool IncludeAllDerivedTypes { get; set; }
+
         public MemberList ConfiguredMemberList { get; set; }
 
         public IEnumerable<TypePair> IncludedDerivedTypes => _includedDerivedTypes;

src/UnitTests/MappingInheritance/IncludeAllDerived.cs

@@ -0,0 +1,45 @@
+using Shouldly;
+using Xunit;
+
+namespace AutoMapper.UnitTests.MappingInheritance
+{
+    public class IncludeAllDerived : AutoMapperSpecBase
+    {
+        public class A
+        {
+            public int Value { get; set; }
+        }
+        public class B : A { }
+        public class C : B { }
+        public class D : A { }
+
+        public class ADto
+        {
+            public int Value { get; set; }
+        }
+
+        public class BDto : ADto { }
+        public class CDto : BDto { }
+        public class DDto : ADto { }
+
+        protected override MapperConfiguration Configuration { get; } = new MapperConfiguration(cfg =>
+        {
+            cfg.CreateMap<A, ADto>()
+                .ForMember(d => d.Value, opt => opt.MapFrom(src => 5))
+                .IncludeAllDerived();
+
+            cfg.CreateMap<B, BDto>();
+            cfg.CreateMap<C, CDto>();
+            cfg.CreateMap<D, DDto>();
+        });
+
+        [Fact]
+        public void Should_apply_configuration_to_all_derived()
+        {
+            Mapper.Map<ADto>(new A {Value = 10}).Value.ShouldBe(5);
+            Mapper.Map<BDto>(new B {Value = 10}).Value.ShouldBe(5);
+            Mapper.Map<CDto>(new C {Value = 10}).Value.ShouldBe(5);
+            Mapper.Map<DDto>(new D {Value = 10}).Value.ShouldBe(5);
+        }
+    }
+}