Allow removing the discriminator for entity types that are not part o…

…f a hierarchy.

Part of #12086

src/EFCore/Metadata/Builders/EntityTypeBuilder.cs

@@ -859,21 +859,19 @@ public virtual DataBuilder HasData([NotNull] IEnumerable<object> data)
         }
 
         /// <summary>
-        ///     Configures the discriminator column used to identify which entity type each row in a table represents
-        ///     when an inheritance hierarchy is mapped to a single table in a relational database.
+        ///     Configures the discriminator property used to identify the entity type in the store.
         /// </summary>
-        /// <returns> A builder that allows the discriminator column to be configured. </returns>
+        /// <returns> A builder that allows the discriminator property to be configured. </returns>
         public virtual DiscriminatorBuilder HasDiscriminator()
             => Builder.DiscriminatorBuilder(
                 Builder.GetOrCreateDiscriminatorProperty(null, null, true), ConfigurationSource.Explicit);
 
         /// <summary>
-        ///     Configures the discriminator column used to identify which entity type each row in a table represents
-        ///     when an inheritance hierarchy is mapped to a single table in a relational database.
+        ///     Configures the discriminator property used to identify the entity type in the store.
         /// </summary>
-        /// <param name="name"> The name of the discriminator column. </param>
-        /// <param name="type"> The type of values stored in the discriminator column. </param>
-        /// <returns> A builder that allows the discriminator column to be configured. </returns>
+        /// <param name="name"> The name of the discriminator property. </param>
+        /// <param name="type"> The type of values stored in the discriminator property. </param>
+        /// <returns> A builder that allows the discriminator property to be configured. </returns>
         public virtual DiscriminatorBuilder HasDiscriminator(
             [NotNull] string name,
             [NotNull] Type type)
@@ -885,12 +883,11 @@ public virtual DiscriminatorBuilder HasDiscriminator(
         }
 
         /// <summary>
-        ///     Configures the discriminator column used to identify which entity type each row in a table represents
-        ///     when an inheritance hierarchy is mapped to a single table in a relational database.
+        ///     Configures the discriminator property used to identify the entity type in the store.
         /// </summary>
-        /// <typeparam name="TDiscriminator"> The type of values stored in the discriminator column. </typeparam>
-        /// <param name="name"> The name of the discriminator column. </param>
-        /// <returns> A builder that allows the discriminator column to be configured. </returns>
+        /// <typeparam name="TDiscriminator"> The type of values stored in the discriminator property. </typeparam>
+        /// <param name="name"> The name of the discriminator property. </param>
+        /// <returns> A builder that allows the discriminator property to be configured. </returns>
         public virtual DiscriminatorBuilder<TDiscriminator> HasDiscriminator<TDiscriminator>([NotNull] string name)
         {
             Check.NotEmpty(name, nameof(name));
@@ -899,6 +896,16 @@ public virtual DiscriminatorBuilder<TDiscriminator> HasDiscriminator<TDiscrimina
                 Builder.DiscriminatorBuilder(Property(typeof(TDiscriminator), name).GetInfrastructure(), ConfigurationSource.Explicit));
         }
 
+        /// <summary>
+        ///     Configures the entity type as having no discriminator property.
+        /// </summary>
+        /// <returns> The same builder instance so that multiple configuration calls can be chained. </returns>
+        public virtual EntityTypeBuilder HasNoDiscriminator()
+        {
+            Builder.HasNoDeclaredDiscriminator(ConfigurationSource.Explicit);
+            return this;
+        }
+
         #region Hidden System.Object members
 
         /// <summary>

src/EFCore/Metadata/Builders/EntityTypeBuilder`.cs

@@ -756,15 +756,14 @@ public virtual DataBuilder<TEntity> HasData([NotNull] IEnumerable<TEntity> data)
         }
 
         /// <summary>
-        ///     Configures the discriminator column used to identify which entity type each row in a table represents
-        ///     when an inheritance hierarchy is mapped to a single table in a relational database.
+        ///     Configures the discriminator property used to identify the entity type in the store.
         /// </summary>
-        /// <typeparam name="TDiscriminator"> The type of values stored in the discriminator column. </typeparam>
+        /// <typeparam name="TDiscriminator"> The type of values stored in the discriminator property. </typeparam>
         /// <param name="propertyExpression">
         ///     A lambda expression representing the property to be used as the discriminator (
         ///     <c>blog => blog.Discriminator</c>).
         /// </param>
-        /// <returns> A builder that allows the discriminator column to be configured. </returns>
+        /// <returns> A builder that allows the discriminator property to be configured. </returns>
         public virtual DiscriminatorBuilder<TDiscriminator> HasDiscriminator<TDiscriminator>(
             [NotNull] Expression<Func<TEntity, TDiscriminator>> propertyExpression)
         {
@@ -774,6 +773,13 @@ public virtual DiscriminatorBuilder<TDiscriminator> HasDiscriminator<TDiscrimina
                Builder.DiscriminatorBuilder(Property(propertyExpression).GetInfrastructure(), ConfigurationSource.Explicit));
         }
 
+        /// <summary>
+        ///     Configures the entity type as having no discriminator property.
+        /// </summary>
+        /// <returns> The same builder instance so that multiple configuration calls can be chained. </returns>
+        public new virtual EntityTypeBuilder<TEntity> HasNoDiscriminator()
+            => (EntityTypeBuilder<TEntity>)base.HasNoDiscriminator();
+
         private InternalEntityTypeBuilder Builder => this.GetInfrastructure();
     }
 }

src/EFCore/Metadata/Internal/EntityType.cs

@@ -2519,23 +2519,27 @@ public virtual void SetDiscriminatorProperty([CanBeNull] IProperty property, Con
         {
             CheckDiscriminatorProperty(property);
 
-            if (property != null
-                && !property.ClrType.IsInstanceOfType(this.GetDiscriminatorValue()))
+            if ((property == null
+                 || !property.ClrType.IsInstanceOfType(this.GetDiscriminatorValue())))
             {
-                foreach (var derivedType in GetDerivedTypesInclusive())
+                ((IMutableEntityType)this).RemoveDiscriminatorValue();
+                if (BaseType == null)
                 {
-                    ((IMutableEntityType)derivedType).RemoveDiscriminatorValue();
+                    foreach (var derivedType in GetDerivedTypes())
+                    {
+                        ((IMutableEntityType)derivedType).RemoveDiscriminatorValue();
+                    }
                 }
             }
 
-            this.SetOrRemoveAnnotation(CoreAnnotationNames.DiscriminatorProperty, property?.Name, configurationSource);
+            SetAnnotation(CoreAnnotationNames.DiscriminatorProperty, property?.Name, configurationSource);
         }
 
         private void CheckDiscriminatorProperty(IProperty property)
         {
             if (property != null)
             {
-                if (this != RootType())
+                if (BaseType != null)
                 {
                     throw new InvalidOperationException(
                         CoreStrings.DiscriminatorPropertyMustBeOnRoot(this.DisplayName()));

src/EFCore/Metadata/Internal/InternalEntityTypeBuilder.cs

@@ -3374,9 +3374,38 @@ public virtual DiscriminatorBuilder DiscriminatorBuilder(
             discriminatorPropertyBuilder = rootTypeBuilder.Property(
                 discriminatorProperty.ClrType, discriminatorProperty.Name, null, ConfigurationSource.Convention);
 
+            RemoveUnusedDiscriminatorProperty(discriminatorProperty, configurationSource);
+
+            rootTypeBuilder.Metadata.SetDiscriminatorProperty(discriminatorProperty, configurationSource);
+            discriminatorPropertyBuilder.IsRequired(true, configurationSource);
+            discriminatorPropertyBuilder.HasValueGenerator(DiscriminatorValueGenerator.Factory, configurationSource);
+
+            return new DiscriminatorBuilder(Metadata);
+        }
+
+        public virtual InternalEntityTypeBuilder HasNoDeclaredDiscriminator(ConfigurationSource configurationSource)
+        {
+            if (Metadata[CoreAnnotationNames.DiscriminatorProperty] != null
+                && !configurationSource.Overrides(Metadata.GetDiscriminatorPropertyConfigurationSource()))
+            {
+                return null;
+            }
+
+            if (Metadata.BaseType == null)
+            {
+                RemoveUnusedDiscriminatorProperty(null, configurationSource);
+            }
+
+            Metadata.SetDiscriminatorProperty(null, configurationSource);
+
+            return this;
+        }
+
+        private void RemoveUnusedDiscriminatorProperty(Property newDiscriminatorProperty, ConfigurationSource configurationSource)
+        {
             var oldDiscriminatorProperty = Metadata.GetDiscriminatorProperty() as Property;
             if (oldDiscriminatorProperty?.Builder != null
-                && oldDiscriminatorProperty != discriminatorProperty)
+                && oldDiscriminatorProperty != newDiscriminatorProperty)
             {
                 oldDiscriminatorProperty.DeclaringEntityType.Builder.RemoveUnusedShadowProperties(
                     new[]
@@ -3390,23 +3419,16 @@ public virtual DiscriminatorBuilder DiscriminatorBuilder(
                     oldDiscriminatorProperty.Builder.HasValueGenerator((Type)null, configurationSource);
                 }
             }
-
-            rootTypeBuilder.Metadata.SetDiscriminatorProperty(discriminatorProperty, configurationSource);
-            discriminatorPropertyBuilder.IsRequired(true, configurationSource);
-            discriminatorPropertyBuilder.HasValueGenerator(DiscriminatorValueGenerator.Factory, configurationSource);
-
-            return new DiscriminatorBuilder(Metadata);
         }
 
         private bool CanSetDiscriminator(
             IProperty discriminatorProperty,
             string name,
             Type discriminatorType,
             bool fromDataAnnotation)
-            => discriminatorProperty == null
-               || ((name != null || discriminatorType != null)
-                   && (name == null || discriminatorProperty.Name == name)
-                   && (discriminatorType == null || discriminatorProperty.ClrType == discriminatorType))
+            => (name == null && discriminatorType == null)
+               || ((name == null || discriminatorProperty?.Name == name)
+                   && (discriminatorType == null || discriminatorProperty?.ClrType == discriminatorType))
                || (fromDataAnnotation ? ConfigurationSource.DataAnnotation : ConfigurationSource.Convention)
                .Overrides(Metadata.GetDiscriminatorPropertyConfigurationSource());
 
@@ -3745,31 +3767,7 @@ IConventionDiscriminatorBuilder IConventionEntityTypeBuilder.HasDiscriminator(Me
 
         /// <inheritdoc />
         IConventionEntityTypeBuilder IConventionEntityTypeBuilder.HasNoDeclaredDiscriminator(bool fromDataAnnotation)
-        {
-            var discriminatorName = (string)Metadata[CoreAnnotationNames.DiscriminatorProperty];
-            if (discriminatorName == null)
-            {
-                return this;
-            }
-
-            var discriminatorProperty = Metadata.FindProperty(discriminatorName);
-            if (discriminatorProperty != null)
-            {
-                if (!CanSetDiscriminator(discriminatorProperty, null, null, fromDataAnnotation))
-                {
-                    return null;
-                }
-
-                discriminatorProperty.DeclaringEntityType.Builder.RemoveUnusedShadowProperties(
-                    new[]
-                    {
-                        discriminatorProperty
-                    });
-            }
-
-            Metadata.SetDiscriminatorProperty(null, fromDataAnnotation);
-            return this;
-        }
+            => HasNoDeclaredDiscriminator(fromDataAnnotation ? ConfigurationSource.DataAnnotation : ConfigurationSource.Convention);
 
         /// <inheritdoc />
         bool IConventionEntityTypeBuilder.CanSetDiscriminator(string name, bool fromDataAnnotation)

test/EFCore.Cosmos.Tests/Metadata/CosmosBuilderExtensionsTest.cs

@@ -34,6 +34,33 @@ public void Default_container_name_is_used_if_not_set()
             Assert.Equal("db1", entityType.GetCosmosContainerName());
         }
 
+        [ConditionalFact]
+        public void Default_discriminator_can_be_removed()
+        {
+            var modelBuilder = CreateConventionModelBuilder();
+
+            modelBuilder.Entity<Customer>();
+
+            var entityType = modelBuilder.Model.FindEntityType(typeof(Customer));
+
+            Assert.Equal("Discriminator", entityType.GetDiscriminatorProperty().Name);
+            Assert.Equal(nameof(Customer), entityType.GetDiscriminatorValue());
+
+            modelBuilder.Entity<Customer>().HasNoDiscriminator();
+
+            Assert.Null(entityType.GetDiscriminatorProperty());
+            Assert.Null(entityType.GetDiscriminatorValue());
+
+            modelBuilder.Entity<Customer>().HasBaseType<object>();
+
+            Assert.Equal("Discriminator", entityType.GetDiscriminatorProperty().Name);
+            Assert.Equal(nameof(Customer), entityType.GetDiscriminatorValue());
+
+            modelBuilder.Entity<Customer>().HasBaseType((string)null);
+
+            Assert.Null(entityType.GetDiscriminatorProperty());
+        }
+
         protected virtual ModelBuilder CreateConventionModelBuilder() => CosmosTestHelpers.Instance.CreateConventionBuilder();
 
         private class Customer

test/EFCore.Tests/Metadata/Conventions/Internal/BackingFieldConventionTest.cs → test/EFCore.Tests/Metadata/Conventions/BackingFieldConventionTest.cs

@@ -6,6 +6,7 @@
 using Microsoft.EntityFrameworkCore.Diagnostics;
 using Microsoft.EntityFrameworkCore.Metadata.Builders;
 using Microsoft.EntityFrameworkCore.Metadata.Conventions.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal;
 using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.EntityFrameworkCore.TestUtilities;
 using Microsoft.Extensions.DependencyInjection;
@@ -21,7 +22,7 @@
 
 #pragma warning disable RCS1213 // Remove unused member declaration.
 
-namespace Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
 {
     public class BackingFieldConventionTest
     {

test/EFCore.Tests/Metadata/Conventions/Internal/BaseTypeDiscoveryConventionTest.cs → test/EFCore.Tests/Metadata/Conventions/BaseTypeDiscoveryConventionTest.cs

@@ -3,12 +3,13 @@
 
 using Microsoft.EntityFrameworkCore.Metadata.Builders;
 using Microsoft.EntityFrameworkCore.Metadata.Conventions.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal;
 using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.EntityFrameworkCore.TestUtilities;
 using Microsoft.Extensions.DependencyInjection;
 using Xunit;
 
-namespace Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
 {
     public class BaseTypeDiscoveryConventionTest
     {

test/EFCore.Tests/Metadata/Conventions/Internal/CascadeDeleteConventionTest.cs → test/EFCore.Tests/Metadata/Conventions/CascadeDeleteConventionTest.cs

@@ -10,7 +10,7 @@
 // ReSharper disable ClassNeverInstantiated.Local
 // ReSharper disable CollectionNeverUpdated.Local
 // ReSharper disable InconsistentNaming
-namespace Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
 {
     public class CascadeDeleteConventionTest
     {

test/EFCore.Tests/Metadata/Conventions/Internal/ConstructorBindingConventionTest.cs → test/EFCore.Tests/Metadata/Conventions/ConstructorBindingConventionTest.cs

@@ -8,6 +8,7 @@
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Metadata.Builders;
 using Microsoft.EntityFrameworkCore.Metadata.Conventions.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal;
 using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.EntityFrameworkCore.TestUtilities;
 using Microsoft.Extensions.DependencyInjection;
@@ -21,7 +22,7 @@
 // ReSharper disable MemberCanBePrivate.Local
 // ReSharper disable MemberHidesStaticFromOuterClass
 // ReSharper disable InconsistentNaming
-namespace Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
 {
     public class ConstructorBindingConventionTest
     {

test/EFCore.Tests/Metadata/Conventions/Internal/ConventionDispatcherTest.cs → test/EFCore.Tests/Metadata/Conventions/ConventionDispatcherTest.cs

@@ -11,7 +11,7 @@
 using Xunit;
 
 // ReSharper disable InconsistentNaming
-namespace Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
 {
     public class ConventionDispatcherTest
     {

test/EFCore.Tests/Metadata/Conventions/Internal/DerivedTypeDiscoveryConventionTest.cs → test/EFCore.Tests/Metadata/Conventions/DerivedTypeDiscoveryConventionTest.cs

@@ -3,12 +3,13 @@
 
 using Microsoft.EntityFrameworkCore.Metadata.Builders;
 using Microsoft.EntityFrameworkCore.Metadata.Conventions.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal;
 using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.EntityFrameworkCore.TestUtilities;
 using Microsoft.Extensions.DependencyInjection;
 using Xunit;
 
-namespace Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
 {
     public class DerivedTypeDiscoveryConventionTest
     {

test/EFCore.Relational.Tests/Metadata/Conventions/Internal/DiscriminatorConventionTest.cs → test/EFCore.Tests/Metadata/Conventions/DiscriminatorConventionTest.cs

@@ -5,14 +5,15 @@
 using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.EntityFrameworkCore.Metadata.Builders;
 using Microsoft.EntityFrameworkCore.Metadata.Conventions.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal;
 using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.EntityFrameworkCore.TestUtilities;
 using Microsoft.Extensions.DependencyInjection;
 using Xunit;
 
 // ReSharper disable UnusedMember.Local
 // ReSharper disable InconsistentNaming
-namespace Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
 {
     public class DiscriminatorConventionTest
     {
@@ -163,7 +164,7 @@ private void RunConvention(InternalEntityTypeBuilder entityTypeBuilder, EntityTy
         }
 
         private ProviderConventionSetBuilderDependencies CreateDependencies()
-            => RelationalTestHelpers.Instance.CreateContextServices().GetRequiredService<ProviderConventionSetBuilderDependencies>();
+            => InMemoryTestHelpers.Instance.CreateContextServices().GetRequiredService<ProviderConventionSetBuilderDependencies>();
 
         private class EntityBase
         {

test/EFCore.Tests/Metadata/Conventions/Internal/EntityTypeAttributeConventionTest.cs → test/EFCore.Tests/Metadata/Conventions/EntityTypeAttributeConventionTest.cs

@@ -5,14 +5,15 @@
 using System.Linq;
 using Microsoft.EntityFrameworkCore.Metadata.Builders;
 using Microsoft.EntityFrameworkCore.Metadata.Conventions.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal;
 using Microsoft.EntityFrameworkCore.Metadata.Internal;
 using Microsoft.EntityFrameworkCore.TestUtilities;
 using Microsoft.Extensions.DependencyInjection;
 using Xunit;
 
 // ReSharper disable UnusedMember.Local
 // ReSharper disable InconsistentNaming
-namespace Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
 {
     public class EntityTypeAttributeConventionTest
     {

test/EFCore.Tests/Metadata/Conventions/Internal/ForeignKeyIndexConventionTest.cs → test/EFCore.Tests/Metadata/Conventions/ForeignKeyIndexConventionTest.cs

@@ -7,7 +7,7 @@
 // ReSharper disable ClassNeverInstantiated.Local
 // ReSharper disable ClassWithVirtualMembersNeverInherited.Local
 // ReSharper disable InconsistentNaming
-namespace Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
 {
     public class ForeignKeyIndexConventionTest
     {