Fix for AutoMapping issue wuth UseUnionSubclassForInheritanceMapping on Overrided mappings

Author: Gutek

src/FluentNHibernate.Testing/AutoMapping/UnionSubclassConventionTests.cs

@@ -0,0 +1,22 @@
+using FluentNHibernate.Automapping;
+using FluentNHibernate.Automapping.TestFixtures.SuperTypes;
+using NUnit.Framework;
+
+namespace FluentNHibernate.Testing.Automapping
+{
+    [TestFixture]
+    public class UnionSubclassConventionTests
+    {
+        [Test]
+        public void DefaultConventionsAreAppliedToUnionSubClasses()
+        {
+            new AutoMappingTester<SuperType>(
+                AutoMap.AssemblyOf<SuperType>()
+                    .Where(x => x.Namespace == typeof(SuperType).Namespace)
+                    .Override<SuperType>(m => m.UseUnionSubclassForInheritanceMapping()))
+                .Element("class/union-subclass[@name='" + typeof(ExampleClass).AssemblyQualifiedName + "']/many-to-one/column")
+                .HasAttribute("name", "Parent_id");
+            //.Element("class/union-subclass").Exists();
+        }
+    }
+}

src/FluentNHibernate.Testing/AutoMapping/UnionSubclassTests.cs

@@ -0,0 +1,20 @@
+using FluentNHibernate.Automapping;
+using FluentNHibernate.Automapping.TestFixtures.SuperTypes;
+using NUnit.Framework;
+
+namespace FluentNHibernate.Testing.Automapping
+{
+    [TestFixture]
+    public class UnionSubclassTests
+    {
+        [Test]
+        public void WhenOverloadedWithUseUnionSubclassForInheritanceMappingUnionSubclassElementShouldExists()
+        {
+            new AutoMappingTester<SuperType>(
+                AutoMap.AssemblyOf<SuperType>()
+                    .Where(x => x.Namespace == typeof(SuperType).Namespace)
+                    .Override<SuperType>(m => m.UseUnionSubclassForInheritanceMapping()))
+                .Element("class/union-subclass").Exists();
+        }
+    }
+}

src/FluentNHibernate.Testing/FluentNHibernate.Testing.csproj

@@ -121,6 +121,8 @@
     <Compile Include="AutoMapping\Overrides\CompositeIdOverrides.cs" />
     <Compile Include="AutoMapping\Overrides\HibernateMappingOverrides.cs" />
     <Compile Include="AutoMapping\Overrides\ParentOverridesWithSubclasses.cs" />
+    <Compile Include="AutoMapping\UnionSubclassConventionTests.cs" />
+    <Compile Include="AutoMapping\UnionSubclassTests.cs" />
     <Compile Include="StubTypeSource.cs" />
     <Compile Include="AutoMapping\TestFixtures.cs" />
     <Compile Include="Cfg\Db\DB2ConfigurationTester.cs" />

src/FluentNHibernate/Automapping/AutoMapper.cs

@@ -58,7 +58,9 @@ private void MapInheritanceTree(Type classType, ClassMappingBase mapping, IList<
                 .Where(x => x.Value != null && x.Value.Type == classType)
                 .Select(x => x.Key))
             {
-                if (isDiscriminated && !discriminatorSet && mapping is ClassMapping)
+                var tempMapping = mapping as ClassMapping;
+                var tempIsNull = tempMapping == null;
+                if (isDiscriminated && !discriminatorSet && !tempIsNull)
                 {
                     var discriminatorColumn = cfg.GetDiscriminatorColumn(classType);
                     var discriminator = new DiscriminatorMapping
@@ -68,13 +70,20 @@ private void MapInheritanceTree(Type classType, ClassMappingBase mapping, IList<
                     };
                     discriminator.AddDefaultColumn(new ColumnMapping { Name = discriminatorColumn });
 
-                    ((ClassMapping)mapping).Discriminator = discriminator;
+                    tempMapping.Discriminator = discriminator;
                     discriminatorSet = true;
                 }
 
                 SubclassMapping subclassMapping;
 
-                if (!isDiscriminated)
+                if(!tempIsNull && tempMapping.IsUnionSubclass)
+                {
+                    subclassMapping = new SubclassMapping(SubclassType.UnionSubclass)
+                    {
+                        Type = inheritedClass.Type
+                    };
+                }
+                else if(!isDiscriminated)
                 {
                     subclassMapping = new SubclassMapping(SubclassType.JoinedSubclass)
                     {