Fix sub-inheritance mapping attributes generation (#347)

* 1. Fix sub-inheritance mapping attributes generation

* 1. Simplification

(cherry picked from commit 7d8ffea)
(cherry picked from commit 8f7d7b5)
(cherry picked from commit 24f2361)
(cherry picked from commit 4383a1d)

# Conflicts:
#	Source/LinqToDB.EntityFrameworkCore/EFCoreMetadataReader.cs

Author: tarasverq

Source/LinqToDB.EntityFrameworkCore/EFCoreMetadataReader.cs

@@ -107,17 +107,12 @@ public MappingAttribute[] GetAttributes(Type type)
 				// InheritanceMappingAttribute
 				if (_model != null)
 				{
-					var derivedEntities = _model.GetEntityTypes().Where(e => e.BaseType == et && e.Relational().DiscriminatorValue != null).ToList();
-
-					foreach (var e in derivedEntities)
+					foreach (var e in _model.GetEntityTypes())
 					{
-						result.Add(
-							new InheritanceMappingAttribute()
+						if (GetBaseTypeRecursive(e) == et && e.GetDiscriminatorValue() != null)
 							{
-								Type = e.ClrType,
-								Code = e.Relational().DiscriminatorValue
+							result.AddRange(GetMappingAttributesRecursive(e));
 							}
-							);
 					}
 				}
 			}
@@ -132,6 +127,31 @@ public MappingAttribute[] GetAttributes(Type type)
 			return result == null ? Array.Empty<MappingAttribute>() : result.ToArray();
 		}
 
+		static IEntityType GetBaseTypeRecursive(IEntityType entityType)
+		{
+			if (entityType.BaseType == null)
+				return entityType;
+			return GetBaseTypeRecursive(entityType.BaseType);
+		}
+		
+		static IEnumerable<InheritanceMappingAttribute> GetMappingAttributesRecursive(IEntityType entityType)
+		{
+			var mappings = new List<InheritanceMappingAttribute>();
+			return ProcessEntityType(entityType);
+
+			List<InheritanceMappingAttribute> ProcessEntityType(IEntityType et)
+			{
+				mappings.Add(new()
+				{
+					Type = et.ClrType, Code = entityType.GetDiscriminatorValue()
+				});
+				
+				if (et.BaseType == null)
+					return mappings;
+				return ProcessEntityType(et.BaseType);
+			}
+		}
+
 		static bool CompareProperty(MemberInfo? property, MemberInfo memberInfo)
 		{
 			if (property == memberInfo)

Tests/LinqToDB.EntityFrameworkCore.BaseTests/ForMappingTestsBase.cs

@@ -161,5 +161,22 @@ public virtual void TestMappingSchemaCachedWithCustomSchema()
 			pk.IsIdentity.Should().BeFalse();
 			Assert.AreEqual("Field", pk.ColumnName);
 		}
+
+		[Test]
+		public virtual async Task TestInheritance()
+		{
+			using var context = CreateContext();
+			using var connection = context.CreateLinqToDBConnection();
+			
+			context.WithInheritance.AddRange(new List<WithInheritanceA1>() { new() { }, new() { } });
+			context.WithInheritance.AddRange(new List<WithInheritanceA2>() { new() { }, new() { } });
+			await context.SaveChangesAsync();
+
+			var result = context.GetTable<WithInheritanceA>().ToList();
+			
+			result.OfType<WithInheritance>().Should().HaveCount(4);
+			result.OfType<WithInheritanceA1>().Should().HaveCount(2);
+			result.OfType<WithInheritanceA2>().Should().HaveCount(2);
+		}
 	}
 }

Tests/LinqToDB.EntityFrameworkCore.BaseTests/Models/ForMapping/ForMappingContextBase.cs

@@ -14,5 +14,10 @@ protected ForMappingContextBase(DbContextOptions options) : base(options)
 		public DbSet<StringTypes> StringTypes { get; set; } = null!;
 
 		public DbSet<WithDuplicateProperties> WithDuplicateProperties { get; set; } = null!;
+		
+		public DbSet<WithInheritance> WithInheritance { get; set; } = null!;
+		public DbSet<WithInheritanceA> WithInheritanceA { get; set; } = null!;
+		public DbSet<WithInheritanceA1> WithInheritanceA1 { get; set; } = null!;
+		public DbSet<WithInheritanceA2> WithInheritanceA2 { get; set; } = null!;
 	}
 }

Tests/LinqToDB.EntityFrameworkCore.BaseTests/Models/ForMapping/WithInheritance.cs

@@ -0,0 +1,22 @@
+namespace LinqToDB.EntityFrameworkCore.BaseTests.Models.ForMapping;
+
+public class WithInheritance
+{
+	public int Id { get; set; }
+	public string Discriminator { get; set; } = null!;
+}
+
+public class WithInheritanceA : WithInheritance
+{
+	
+}
+
+public class WithInheritanceA1 : WithInheritanceA
+{
+	
+}
+
+public class WithInheritanceA2 : WithInheritanceA
+{
+	
+}

Tests/LinqToDB.EntityFrameworkCore.PomeloMySql.Tests/Models/ForMapping/ForMappingContext.cs

@@ -25,6 +25,11 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
 			{
 				b.HasKey(e => e.Id);
 			});
+			
+			modelBuilder.Entity<WithInheritance>(b =>
+			{
+				b.HasDiscriminator(x => x.Discriminator);
+			});
 		}
 	}
 }

Tests/LinqToDB.EntityFrameworkCore.PostgreSQL.Tests/Models/ForMapping/ForMappingContext.cs

@@ -25,6 +25,11 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
 			{
 				b.HasKey(e => e.Id);
 			});
+			
+			modelBuilder.Entity<WithInheritance>(b =>
+			{
+				b.HasDiscriminator(x => x.Discriminator);
+			});
 		}
 	}
 }

Tests/LinqToDB.EntityFrameworkCore.SQLite.Tests/Models/ForMapping/ForMappingContext.cs

@@ -22,6 +22,11 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
 			{
 				b.HasKey(e => e.Id);
 			});
+			
+			modelBuilder.Entity<WithInheritance>(b =>
+			{
+				b.HasDiscriminator(x => x.Discriminator);
+			});
 		}
 	}
 }

Tests/LinqToDB.EntityFrameworkCore.SqlServer.Tests/Models/ForMapping/ForMappingContext.cs

@@ -32,6 +32,11 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
 					b.Property(e => e.UnicodeString).HasMaxLength(50).IsUnicode();
 				}
 			);
+			
+			modelBuilder.Entity<WithInheritance>(b =>
+			{
+				b.HasDiscriminator(x => x.Discriminator);
+			});
 		}
 	}
 }