Support for different map-to-null conditions for derived types

Author: SteveWilkes

AgileMapper.UnitTests/Configuration/WhenMappingToNull.cs

@@ -93,6 +93,43 @@ public void ShouldOverwriteAPropertyToNull()
             }
         }
 
+        [Fact]
+        public void ShouldApplyConfiguredConditionsToDerivedTypes()
+        {
+            using (var mapper = Mapper.CreateNew())
+            {
+                mapper.WhenMapping
+                    .To<Product>()
+                    .If((o, p) => p.Price.Equals(0))
+                    .MapToNull();
+
+                mapper.WhenMapping
+                    .To<MegaProduct>()
+                    .If((o, p) => p.HowMega == 0)
+                    .MapToNull();
+
+                var nonMatchingProductSource = new { Price = 123 };
+                var nonMatchingProductResult = mapper.Map(nonMatchingProductSource).ToANew<Product>();
+
+                nonMatchingProductResult.Price.ShouldBe(123);
+
+                var matchingProductSource = new { Price = 0 };
+                var matchingProductResult = mapper.Map(matchingProductSource).ToANew<Product>();
+
+                matchingProductResult.ShouldBeNull();
+
+                var nonMatchingMegaProductSource = new { HowMega = 0.99 };
+                var nonMatchingMegaProductResult = mapper.Map(nonMatchingMegaProductSource).ToANew<MegaProduct>();
+
+                nonMatchingMegaProductResult.HowMega.ShouldBe(0.99);
+
+                var matchingMegaProductSource = new { HowMega = 0.00 };
+                var matchingMegaProductResult = mapper.Map(matchingMegaProductSource).ToANew<MegaProduct>();
+
+                matchingMegaProductResult.ShouldBeNull();
+            }
+        }
+
         [Fact]
         public void ShouldErrorIfConditionsAreConfiguredForTheSameType()
         {

AgileMapper/Configuration/MapToNullCondition.cs

@@ -1,17 +1,26 @@
 namespace AgileObjects.AgileMapper.Configuration
 {
+    using System;
     using System.Linq.Expressions;
     using Members;
     using ObjectPopulation;
 
     internal class MapToNullCondition : UserConfiguredItemBase
     {
+        private readonly Type _targetType;
+
         public MapToNullCondition(MappingConfigInfo configInfo)
             : base(configInfo)
         {
+            _targetType = configInfo.TargetType;
         }
 
-        protected override bool ConditionsAvoidConflict(UserConfiguredItemBase otherConfiguredItem) => false;
+        public override bool ConflictsWith(UserConfiguredItemBase otherConfiguredItem)
+        {
+            var otherCondition = (MapToNullCondition)otherConfiguredItem;
+
+            return otherCondition._targetType == _targetType;
+        }
 
         protected override Expression GetConditionOrNull(IMemberMapperData mapperData, CallbackPosition position)
         {

AgileMapper/Configuration/MappingConfigInfo.cs

@@ -74,6 +74,9 @@ public MappingConfigInfo ForTargetType(Type targetType)
             return this;
         }
 
+        public bool IsForTargetType(MappingConfigInfo otherConfigInfo)
+            => TargetType.IsAssignableFrom(otherConfigInfo.TargetType);
+
         public bool HasSameTargetTypeAs(MappingConfigInfo otherConfigInfo) => TargetType == otherConfigInfo.TargetType;
 
         public bool HasCompatibleTypes(MappingConfigInfo otherConfigInfo)

AgileMapper/Configuration/UserConfigurationSet.cs

@@ -12,7 +12,7 @@
     internal class UserConfigurationSet
     {
         private readonly ICollection<ObjectTrackingMode> _trackingModeSettings;
-        private readonly ICollection<MapToNullCondition> _mapToNullConditions;
+        private readonly List<MapToNullCondition> _mapToNullConditions;
         private readonly ICollection<NullCollectionsSetting> _nullCollectionSettings;
         private readonly ICollection<ConfiguredObjectFactory> _objectFactories;
         private readonly ICollection<ConfiguredIgnoredMember> _ignoredMembers;
@@ -66,6 +66,7 @@ public void Add(MapToNullCondition condition)
                 c => "Type " + c.TargetTypeName + " already has a configured map-to-null condition");
 
             _mapToNullConditions.Add(condition);
+            _mapToNullConditions.Sort();
         }
 
         public Expression GetMapToNullConditionOrNull(IMemberMapperData mapperData)

AgileMapper/Configuration/UserConfiguredItemBase.cs

@@ -51,7 +51,7 @@ protected UserConfiguredItemBase(MappingConfigInfo configInfo, QualifiedMember t
 
         public virtual bool ConflictsWith(UserConfiguredItemBase otherConfiguredItem)
         {
-            if (ConditionsAvoidConflict(otherConfiguredItem))
+            if (HasConfiguredCondition || otherConfiguredItem.HasConfiguredCondition)
             {
                 return false;
             }
@@ -64,9 +64,6 @@ public virtual bool ConflictsWith(UserConfiguredItemBase otherConfiguredItem)
             return false;
         }
 
-        protected virtual bool ConditionsAvoidConflict(UserConfiguredItemBase otherConfiguredItem)
-            => HasConfiguredCondition || otherConfiguredItem.HasConfiguredCondition;
-
         protected virtual bool MembersConflict(QualifiedMember otherMember)
             => TargetMember.Matches(otherMember);
 
@@ -146,7 +143,17 @@ int IComparable<UserConfiguredItemBase>.CompareTo(UserConfiguredItemBase other)
 
             if (ConfigInfo.HasSameSourceTypeAs(other.ConfigInfo))
             {
-                return 0;
+                if (ConfigInfo.HasSameTargetTypeAs(other.ConfigInfo))
+                {
+                    return 0;
+                }
+
+                if (ConfigInfo.IsForTargetType(other.ConfigInfo))
+                {
+                    return 1;
+                }
+
+                return -1;
             }
 
             if (ConfigInfo.IsForSourceType(other.ConfigInfo))