Validate that a recursive complex-typed property must be nullable

src/Microsoft.OData.Edm/Microsoft.OData.Edm.cs

@@ -119,6 +119,7 @@ internal sealed class EdmRes {
         internal const string EdmModel_Validator_Semantic_AmbiguousType = "EdmModel_Validator_Semantic_AmbiguousType";
         internal const string EdmModel_Validator_Semantic_InvalidNavigationPropertyType = "EdmModel_Validator_Semantic_InvalidNavigationPropertyType";
         internal const string EdmModel_Validator_Semantic_NavigationPropertyWithRecursiveContainmentTargetMustBeOptional = "EdmModel_Validator_Semantic_NavigationPropertyWithRecursiveContainmentTargetMustBeOptional";
+        internal const string EdmModel_Validator_Semantic_RecursiveComplexTypedPropertyMustBeOptional = "EdmModel_Validator_Semantic_RecursiveComplexTypedPropertyMustBeOptional";
         internal const string EdmModel_Validator_Semantic_NavigationPropertyWithRecursiveContainmentSourceMustBeFromZeroOrOne = "EdmModel_Validator_Semantic_NavigationPropertyWithRecursiveContainmentSourceMustBeFromZeroOrOne";
         internal const string EdmModel_Validator_Semantic_NavigationPropertyWithNonRecursiveContainmentSourceMustBeFromOne = "EdmModel_Validator_Semantic_NavigationPropertyWithNonRecursiveContainmentSourceMustBeFromOne";
         internal const string EdmModel_Validator_Semantic_ComplexTypeMustHaveProperties = "EdmModel_Validator_Semantic_ComplexTypeMustHaveProperties";

src/Microsoft.OData.Edm/Microsoft.OData.Edm.txt

@@ -103,6 +103,7 @@ EdmModel_Validator_Semantic_InaccessibleType=The named type '{0}' could not be f
 EdmModel_Validator_Semantic_AmbiguousType=The named type '{0}' is ambiguous from the model being validated.
 EdmModel_Validator_Semantic_InvalidNavigationPropertyType=The type of the navigation property '{0}' is invalid. The navigation target type must be an entity type or a collection of entity type. The navigation target entity type must match the declaring type of the partner property.
 EdmModel_Validator_Semantic_NavigationPropertyWithRecursiveContainmentTargetMustBeOptional=The target multiplicity of the navigation property '{0}' is invalid. If a navigation property has 'ContainsTarget' set to true and declaring entity type of the property is the same or inherits from the target entity type, then the property represents a recursive containment and it must have an optional target represented by a collection or a nullable entity type.
+EdmModel_Validator_Semantic_RecursiveComplexTypedPropertyMustBeOptional=The nullability of the property '{0}' is invalid. If a complex typed property is of the same type (or base type) as its declaring type, then the property represents a recursive containment and the given property must be optional.
 EdmModel_Validator_Semantic_NavigationPropertyWithRecursiveContainmentSourceMustBeFromZeroOrOne=The source multiplicity of the navigation property '{0}' is invalid. If a navigation property has 'ContainsTarget' set to true and declaring entity type of the property is the same or inherits from the target entity type, then the property represents a recursive containment and the multiplicity of the navigation source must be zero or one.
 EdmModel_Validator_Semantic_NavigationPropertyWithNonRecursiveContainmentSourceMustBeFromOne=The source multiplicity of the navigation property '{0}' is invalid. If a navigation property has 'ContainsTarget' set to true and declaring entity type of the property is not the same as the target entity type, then the property represents a non-recursive containment and the multiplicity of the navigation source must be exactly one.
 EdmModel_Validator_Semantic_ComplexTypeMustHaveProperties=The complex type '{0}' is invalid. A complex type must contain at least one property.

src/Microsoft.OData.Edm/Parameterized.Microsoft.OData.Edm.cs

@@ -833,6 +833,14 @@ internal static string EdmModel_Validator_Semantic_NavigationPropertyWithRecursi
             return Microsoft.OData.Edm.EdmRes.GetString(Microsoft.OData.Edm.EdmRes.EdmModel_Validator_Semantic_NavigationPropertyWithRecursiveContainmentTargetMustBeOptional, p0);
         }
 
+        /// <summary>
+        /// A string like "The nullability of the property '{0}' is invalid. If a complex typed property is of the same type (or base type) as its declaring type, then the property represents a recursive containment and the given property must be optional."
+        /// </summary>
+        internal static string EdmModel_Validator_Semantic_RecursiveComplexTypedPropertyMustBeOptional(object p0)
+        {
+            return Microsoft.OData.Edm.EdmRes.GetString(Microsoft.OData.Edm.EdmRes.EdmModel_Validator_Semantic_RecursiveComplexTypedPropertyMustBeOptional, p0);
+        }
+
         /// <summary>
         /// A string like "The source multiplicity of the navigation property '{0}' is invalid. If a navigation property has 'ContainsTarget' set to true and declaring entity type of the property is the same or inherits from the target entity type, then the property represents a recursive containment and the multiplicity of the navigation source must be zero or one."
         /// </summary>

src/Microsoft.OData.Edm/Validation/EdmErrorCode.cs

@@ -1432,5 +1432,10 @@ public enum EdmErrorCode
         /// A property is required in an object
         /// </summary>
         MissingRequiredProperty,
+
+        /// <summary>
+        /// A recursive complex-typed property must be optional.
+        /// </summary>
+        RecursiveComplexTypedPropertyMustBeOptional,
     }
 }

src/Microsoft.OData.Edm/Validation/ValidationRules.cs

@@ -1192,6 +1192,37 @@ public static class ValidationRules
                     }
                 });
 
+        // Add this to rule set as a breaking change for a future release.
+        /// <summary>
+        /// Validates that if a complex-typed property has a type or base type that is the same as
+        /// the complex type, then the complex type is nullable.
+        /// </summary>
+        public static readonly ValidationRule<IEdmStructuralProperty> RecursiveComplexTypedPropertyMustBeOptional =
+            new ValidationRule<IEdmStructuralProperty>(
+                (context, property) =>
+                {
+                    IEdmTypeReference currentPropTypeRef = property.Type;
+                    IEdmType currentPropType = currentPropTypeRef.Definition;
+                    IEdmStructuredType declaringType = property.DeclaringType;
+
+                    if (!currentPropTypeRef.IsNullable)
+                    {
+                        while (currentPropType != null && currentPropType != declaringType)
+                        {
+                            IEdmStructuredType baseType = ((IEdmStructuredType)currentPropType).BaseType;
+                            currentPropType = baseType;
+                        }
+
+                        if (currentPropType == declaringType)
+                        {
+                            context.AddError(
+                                property.Location(),
+                                EdmErrorCode.RecursiveComplexTypedPropertyMustBeOptional,
+                                Strings.EdmModel_Validator_Semantic_RecursiveComplexTypedPropertyMustBeOptional(property.Name));
+                        }
+                    }
+                });
+
         #endregion
 
         #region IEdmNavigationProperty

test/FunctionalTests/Microsoft.OData.Edm.Tests/Validation/ValidationRuleSetTests.cs

@@ -25,7 +25,8 @@ public void NewValidationRulesShouldBeInTheRuleSetExceptBaselinedExceptionRules(
                 f.Name != "NavigationPropertyEntityMustNotIndirectlyContainItself" &&
                 f.Name != "EntityTypeKeyMissingOnEntityType" &&
                 f.Name != "VocabularyAnnotationTargetAllowedApplyToElement" &&
-                f.Name != "EntityTypeInvalidKeyKeyDefinedInAncestor")
+                f.Name != "EntityTypeInvalidKeyKeyDefinedInAncestor" && 
+                f.Name != "RecursiveComplexTypedPropertyMustBeOptional")
                 .Select(f=> new KeyValuePair<object, string>(f.GetValue(null), f.Name));
             foreach (var item in items)
             {

test/FunctionalTests/Microsoft.OData.Edm.Tests/Validation/ValidationRulesTests.cs

@@ -795,6 +795,110 @@ public void SameFunctionsShouldInWithOneInReferencedModelShouldRaiseError()
         }
         #endregion
 
+        #region RecursiveComplexTypedPropertyMustBeOptional Tests
+
+        [Fact]
+        public void ComplexTypedPropertyWithSameTypeAsDeclaringTypeShouldError()
+        {
+            EdmComplexType complexType = new EdmComplexType("ns", "myType");
+            IEdmTypeReference complexTypeRef = complexType.GetTypeReference(false);
+            IEdmStructuralProperty nestedProp = complexType.AddStructuralProperty("nested", complexTypeRef);
+
+            ValidateError(
+                ValidationRules.RecursiveComplexTypedPropertyMustBeOptional,
+                nestedProp,
+                EdmErrorCode.RecursiveComplexTypedPropertyMustBeOptional,
+                Strings.EdmModel_Validator_Semantic_RecursiveComplexTypedPropertyMustBeOptional("nested"));
+        }
+
+        [Fact]
+        public void ComplexTypedPropertyWithSameBaseTypeAsDeclaringTypeShouldError()
+        {
+            EdmComplexType baseType = new EdmComplexType("ns", "myType");
+            EdmComplexType derivedType = new EdmComplexType("ns", "derivedType", baseType);
+            IEdmTypeReference derivedTypeRef = derivedType.GetTypeReference(false);
+            IEdmStructuralProperty nestedBaseProp = baseType.AddStructuralProperty("nested", derivedTypeRef);
+
+            ValidateError(
+                ValidationRules.RecursiveComplexTypedPropertyMustBeOptional,
+                nestedBaseProp,
+                EdmErrorCode.RecursiveComplexTypedPropertyMustBeOptional,
+                Strings.EdmModel_Validator_Semantic_RecursiveComplexTypedPropertyMustBeOptional("nested"));
+        }
+
+        [Fact]
+        public void ComplexTypedPropertyWithSameTypeAsDeclaringBaseTypeShouldNotError()
+        {
+            EdmComplexType baseType = new EdmComplexType("ns", "myType");
+            EdmComplexType derivedType = new EdmComplexType("ns", "derivedType", baseType);
+            IEdmTypeReference baseTypeReference = baseType.GetTypeReference(false);
+            IEdmStructuralProperty nestedDerivedProp = derivedType.AddStructuralProperty("nested", baseTypeReference);
+
+            var model = new EdmModel();
+            model.AddElement(baseType);
+            model.AddElement(derivedType);
+
+            ValidateNoError(
+                ValidationRules.RecursiveComplexTypedPropertyMustBeOptional,
+                model,
+                nestedDerivedProp);
+        }
+
+        [Fact]
+        public void ComplexTypedPropertyWithSameInheritedBaseTypeAsDeclaringTypeShouldError()
+        {
+            EdmComplexType baseType = new EdmComplexType("ns", "myType");
+            EdmComplexType derivedType1 = new EdmComplexType("ns", "derivedType1", baseType);
+            EdmComplexType derivedType2 = new EdmComplexType("ns", "derivedType2", derivedType1);
+            IEdmTypeReference derivedType2Ref = derivedType2.GetTypeReference(false);
+            IEdmStructuralProperty nestedBaseProp = baseType.AddStructuralProperty("nested", derivedType2Ref);
+
+            ValidateError(
+                ValidationRules.RecursiveComplexTypedPropertyMustBeOptional,
+                nestedBaseProp,
+                EdmErrorCode.RecursiveComplexTypedPropertyMustBeOptional,
+                Strings.EdmModel_Validator_Semantic_RecursiveComplexTypedPropertyMustBeOptional("nested"));
+        }
+
+        [Fact]
+        public void ComplexTypedPropertyWithSameSecondInheritedBaseTypeAsDeclaringTypeShouldError()
+        {
+            EdmComplexType baseType = new EdmComplexType("ns", "myType");
+            EdmComplexType derivedType1 = new EdmComplexType("ns", "derivedType1", baseType);
+            EdmComplexType derivedType2 = new EdmComplexType("ns", "derivedType2", derivedType1);
+            EdmComplexType derivedType3 = new EdmComplexType("ns", "derivedType3", derivedType2);
+            IEdmTypeReference derivedType3Ref = derivedType3.GetTypeReference(false);
+            IEdmStructuralProperty nestedBaseProp = baseType.AddStructuralProperty("nested", derivedType3Ref);
+
+            ValidateError(
+                ValidationRules.RecursiveComplexTypedPropertyMustBeOptional,
+                nestedBaseProp,
+                EdmErrorCode.RecursiveComplexTypedPropertyMustBeOptional,
+                Strings.EdmModel_Validator_Semantic_RecursiveComplexTypedPropertyMustBeOptional("nested"));
+        }
+
+        [Fact]
+        public void ComplexTypedPropertyWithMutualBaseTypeShouldNotError()
+        {
+            EdmComplexType baseType = new EdmComplexType("ns", "myType");
+            EdmComplexType derivedType = new EdmComplexType("ns", "derivedType", baseType);
+            EdmComplexType otherDerivedType = new EdmComplexType("ns", "otherDerivedType", baseType);
+            IEdmTypeReference derivedTypeRef = derivedType.GetTypeReference(false);
+            IEdmStructuralProperty nestedOtherDerivedProp = otherDerivedType.AddStructuralProperty("nested", derivedTypeRef);
+
+            var model = new EdmModel();
+            model.AddElement(baseType);
+            model.AddElement(derivedType);
+            model.AddElement(otherDerivedType);
+
+            ValidateNoError(
+                ValidationRules.RecursiveComplexTypedPropertyMustBeOptional,
+                model,
+                nestedOtherDerivedProp);
+        }
+
+        #endregion
+
         [Fact]
         public void NavigationPropertyWrongMultiplicityForDependent()
         {

test/PublicApiTests/BaseLine/Microsoft.OData.PublicApi.net45.bsl

@@ -3276,6 +3276,7 @@ public enum Microsoft.OData.Edm.Validation.EdmErrorCode : int {
     RecordExpressionHasExtraProperties = 318
     RecordExpressionMissingRequiredProperty = 317
     RecordExpressionNotValidForNonStructuredType = 316
+    RecursiveComplexTypedPropertyMustBeOptional = 411
     ReferencedTypeMustHaveValidName = 322
     ReferenceElementMustContainAtLeastOneIncludeOrIncludeAnnotationsElement = 372
     ReferentialConstraintPrincipalEndMustBelongToAssociation = 243
@@ -3473,6 +3474,7 @@ public sealed class Microsoft.OData.Edm.Validation.ValidationRules {
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.IEdmProperty]] PropertyTypeCannotBeCollectionOfAbstractType = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.IEdmProperty]
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.Vocabularies.IEdmPropertyValueBinding]] PropertyValueBindingValueIsCorrectType = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.Vocabularies.IEdmPropertyValueBinding]
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.Vocabularies.IEdmRecordExpression]] RecordExpressionPropertiesMatchType = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.Vocabularies.IEdmRecordExpression]
+    public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.IEdmStructuralProperty]] RecursiveComplexTypedPropertyMustBeOptional = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.IEdmStructuralProperty]
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.IEdmSchemaElement]] SchemaElementMustNotHaveKindOfNone = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.IEdmSchemaElement]
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.IEdmSchemaElement]] SchemaElementNamespaceIsNotAllowed = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.IEdmSchemaElement]
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.IEdmSchemaElement]] SchemaElementNamespaceIsTooLong = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.IEdmSchemaElement]

test/PublicApiTests/BaseLine/Microsoft.OData.PublicApi.netstandard1.1.bsl

@@ -3276,6 +3276,7 @@ public enum Microsoft.OData.Edm.Validation.EdmErrorCode : int {
     RecordExpressionHasExtraProperties = 318
     RecordExpressionMissingRequiredProperty = 317
     RecordExpressionNotValidForNonStructuredType = 316
+    RecursiveComplexTypedPropertyMustBeOptional = 411
     ReferencedTypeMustHaveValidName = 322
     ReferenceElementMustContainAtLeastOneIncludeOrIncludeAnnotationsElement = 372
     ReferentialConstraintPrincipalEndMustBelongToAssociation = 243
@@ -3473,6 +3474,7 @@ public sealed class Microsoft.OData.Edm.Validation.ValidationRules {
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.IEdmProperty]] PropertyTypeCannotBeCollectionOfAbstractType = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.IEdmProperty]
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.Vocabularies.IEdmPropertyValueBinding]] PropertyValueBindingValueIsCorrectType = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.Vocabularies.IEdmPropertyValueBinding]
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.Vocabularies.IEdmRecordExpression]] RecordExpressionPropertiesMatchType = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.Vocabularies.IEdmRecordExpression]
+    public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.IEdmStructuralProperty]] RecursiveComplexTypedPropertyMustBeOptional = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.IEdmStructuralProperty]
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.IEdmSchemaElement]] SchemaElementMustNotHaveKindOfNone = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.IEdmSchemaElement]
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.IEdmSchemaElement]] SchemaElementNamespaceIsNotAllowed = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.IEdmSchemaElement]
     public static readonly Microsoft.OData.Edm.Validation.ValidationRule`1[[Microsoft.OData.Edm.IEdmSchemaElement]] SchemaElementNamespaceIsTooLong = Microsoft.OData.Edm.Validation.ValidationRule`1[Microsoft.OData.Edm.IEdmSchemaElement]