Throw if defining query is used on keyed entity type

src/EFCore/Infrastructure/ModelValidator.cs

@@ -72,6 +72,7 @@ public virtual void Validate(IModel model, IDiagnosticsLogger<DbLoggerCategory.M
             ValidateFieldMapping(model, logger);
             ValidateKeylessTypes(model, logger);
             ValidateQueryFilters(model, logger);
+            ValidateDefiningQuery(model, logger);
             ValidateData(model, logger);
             LogShadowProperties(model, logger);
         }
@@ -811,7 +812,7 @@ protected virtual void ValidateKeylessTypes([NotNull] IModel model, [NotNull] ID
                     if (entityType.FindPrimaryKey() != null)
                     {
                         throw new InvalidOperationException(
-                            CoreStrings.NonKeylessEntityTypeDefiningQuery(entityType.DisplayName()));
+                            CoreStrings.DefiningQueryWithKey(entityType.DisplayName()));
                     }
                 }
             }
@@ -828,13 +829,32 @@ protected virtual void ValidateQueryFilters([NotNull] IModel model, [NotNull] ID
 
             foreach (var entityType in model.GetEntityTypes())
             {
-                if (entityType.GetQueryFilter() != null)
+                if (entityType.GetQueryFilter() != null
+                    && entityType.BaseType != null)
                 {
-                    if (entityType.BaseType != null)
-                    {
-                        throw new InvalidOperationException(
-                            CoreStrings.BadFilterDerivedType(entityType.GetQueryFilter(), entityType.DisplayName()));
-                    }
+                    throw new InvalidOperationException(
+                        CoreStrings.BadFilterDerivedType(entityType.GetQueryFilter(), entityType.DisplayName()));
+                }
+            }
+        }
+
+        /// <summary>
+        ///     Validates the mapping/configuration of defining queries in the model.
+        /// </summary>
+        /// <param name="model"> The model to validate. </param>
+        /// <param name="logger"> The logger to use. </param>
+        protected virtual void ValidateDefiningQuery(
+            [NotNull] IModel model, [NotNull] IDiagnosticsLogger<DbLoggerCategory.Model.Validation> logger)
+        {
+            Check.NotNull(model, nameof(model));
+
+            foreach (var entityType in model.GetEntityTypes())
+            {
+                if (entityType.GetDefiningQuery() != null
+                    && entityType.FindPrimaryKey() != null)
+                {
+                    throw new InvalidOperationException(
+                        CoreStrings.DefiningQueryWithKey(entityType.DisplayName()));
                 }
             }
         }

src/EFCore/Properties/CoreStrings.resx

@@ -891,6 +891,9 @@
   <data name="BadFilterDerivedType" xml:space="preserve">
     <value>The filter expression '{filter}' cannot be specified for entity type '{entityType}'. A filter may only be applied to the root entity type in a hierarchy.</value>
   </data>
+  <data name="DefiningQueryWithKey" xml:space="preserve">
+    <value>The entity type '{entityType}' cannot use 'ToQuery' to create a defining query because it also defines a primary key. Defining queries can only be used to back entity types without keys.</value>
+  </data>
   <data name="ConverterPropertyMismatch" xml:space="preserve">
     <value>Converter for model type '{converterType}' cannot be used for '{entityType}.{propertyName}' because its type is '{propertyType}'.</value>
   </data>
@@ -1120,9 +1123,6 @@
   <data name="InvalidSetKeylessOperation" xml:space="preserve">
     <value>The invoked method is cannot be used for the entity type '{entityType}' because it does not have a primary key.</value>
   </data>
-  <data name="NonKeylessEntityTypeDefiningQuery" xml:space="preserve">
-    <value>The entity type '{entityType}' cannot have a defining query because it has a primary key. Only keyless entity types can have a defining query.</value>
-  </data>
   <data name="DerivedEntityTypeHasNoKey" xml:space="preserve">
     <value>A '{derivedType}' cannot be configured as keyless because it is a derived type. The root type '{rootType}' must be configured as keyless. If you did not intend for '{rootType}' to be included in the model, ensure that it is not included in a DbSet property on your context, referenced in a configuration call to ModelBuilder, or referenced from a navigation property on a type that is included in the model.</value>
   </data>

test/EFCore.Tests/Infrastructure/ModelValidatorTest.cs

@@ -31,6 +31,15 @@ public virtual void Detects_filter_on_derived_type()
             VerifyError(CoreStrings.BadFilterDerivedType(entityTypeD.GetQueryFilter(), entityTypeD.DisplayName()), modelBuilder.Model);
         }
 
+        [ConditionalFact]
+        public virtual void Detects_defining_query_on_keyed_entity_type()
+        {
+            var modelBuilder = CreateConventionalModelBuilder();
+            modelBuilder.Entity<A>().ToQuery(() => new List<A>().AsQueryable());
+
+            VerifyError(CoreStrings.DefiningQueryWithKey("A"), modelBuilder.Model);
+        }
+
         [ConditionalFact]
         public virtual void Detects_shadow_entities()
         {

test/EFCore.Tests/Metadata/Internal/EntityTypeTest.cs

@@ -65,12 +65,9 @@ private class FakeEntityType : IEntityType
             public string Name { get; }
             public Type ClrType { get; }
             public IEntityType BaseType { get; }
-            public bool IsKeyless { get; }
             public string DefiningNavigationName { get; }
             public IEntityType DefiningEntityType { get; }
             public LambdaExpression QueryFilter { get; }
-            public LambdaExpression DefiningQuery { get; }
-            public bool IsQueryType { get; }
             public IKey FindPrimaryKey() => throw new NotImplementedException();
             public IKey FindKey(IReadOnlyList<IProperty> properties) => throw new NotImplementedException();
             public IEnumerable<IKey> GetKeys() => throw new NotImplementedException();