Adds discriminator object to complex types which have derived types (#238)

* Add derived types of complex types to discriminator value

* Add test to validate discriminator values added to complex types

* Add release note

Author: irvinesunday

src/Microsoft.OpenApi.OData.Reader/Generator/OpenApiSchemaGenerator.cs

@@ -374,7 +374,7 @@ internal static OpenApiSchema CreateSchemaTypeSchema(this ODataContext context,
         }
 
         private static OpenApiSchema CreateStructuredTypeSchema(this ODataContext context, IEdmStructuredType structuredType, bool processBase, bool processExample,
-            IEnumerable<IEdmEntityType> derivedTypes = null)
+            IEnumerable<IEdmStructuredType> derivedTypes = null)
         {
             Debug.Assert(context != null);
             Debug.Assert(structuredType != null);
@@ -387,7 +387,7 @@ private static OpenApiSchema CreateStructuredTypeSchema(this ODataContext contex
 
             if (context.Settings.EnableDiscriminatorValue && derivedTypes == null)
             {
-                derivedTypes = context.Model.FindDirectlyDerivedTypes(structuredType).OfType<IEdmEntityType>();
+                derivedTypes = context.Model.FindDirectlyDerivedTypes(structuredType);
             }
 
             if (processBase && structuredType.BaseType != null)
@@ -435,8 +435,8 @@ private static OpenApiSchema CreateStructuredTypeSchema(this ODataContext contex
             {
                 // The discriminator object is added to structured types which have derived types.
                 OpenApiDiscriminator discriminator = null;
-                if (context.Settings.EnableDiscriminatorValue && derivedTypes.Any() && structuredType.BaseType != null)
-                {         
+                if (context.Settings.EnableDiscriminatorValue && derivedTypes.Any())
+                {
                     Dictionary<string, string> mapping = derivedTypes
                         .ToDictionary(x => $"#{x.FullTypeName()}", x => new OpenApiSchema
                         {

src/Microsoft.OpenApi.OData.Reader/Microsoft.OpenAPI.OData.Reader.csproj

@@ -15,7 +15,7 @@
     <TargetFrameworks>netstandard2.0</TargetFrameworks>
     <PackageId>Microsoft.OpenApi.OData</PackageId>
     <SignAssembly>true</SignAssembly>
-    <Version>1.0.11-preview2</Version>
+    <Version>1.0.11-preview3</Version>
     <Description>This package contains the codes you need to convert OData CSDL to Open API Document of Model.</Description>
     <Copyright>© Microsoft Corporation. All rights reserved.</Copyright>
     <PackageTags>Microsoft OpenApi OData EDM</PackageTags>
@@ -26,6 +26,7 @@
 - Add error ranges for OData actions when ErrorResponsesAsDefault is set to false #218
 - Fixes missing bound operations on some navigation property paths #201
 - Provides support for using success status code range 2XX #153
+- Adds discriminator object to complex types which have derived types #233
     </PackageReleaseNotes>
     <AssemblyName>Microsoft.OpenApi.OData.Reader</AssemblyName>
     <AssemblyOriginatorKeyFile>..\..\tool\Microsoft.OpenApi.OData.snk</AssemblyOriginatorKeyFile>

test/Microsoft.OpenAPI.OData.Reader.Tests/Generator/OpenApiSchemaGeneratorTests.cs

@@ -81,7 +81,7 @@ public void CreateStructuredTypeSchemaThrowArgumentNullEnumType()
         }
 
         [Fact]
-        public void CreateStructuredTypeSchemaWithDiscriminatorValueEnabledReturnsCorrectSchema()
+        public void CreateStructuredTypeSchemaForEntityTypeWithDiscriminatorValueEnabledReturnsCorrectSchema()
         {
             // Arrange
             IEdmModel model = EdmModelHelper.GraphBetaModel;
@@ -142,6 +142,48 @@ public void CreateStructuredTypeSchemaWithDiscriminatorValueEnabledReturnsCorrec
 }".ChangeLineBreaks(), json);
         }
 
+        [Fact]
+        public void CreateStructuredTypeSchemaForComplexTypeWithDiscriminatorValueEnabledReturnsCorrectSchema()
+        {
+            // Arrange
+            IEdmModel model = EdmModelHelper.GraphBetaModel;
+            ODataContext context = new(model, new OpenApiConvertSettings
+            {
+                EnableDiscriminatorValue = true,
+            });
+
+            IEdmComplexType complex = model.SchemaElements.OfType<IEdmComplexType>().First(t => t.Name == "userSet");
+            Assert.NotNull(complex); // Guard
+
+            // Act
+            var schema = context.CreateStructuredTypeSchema(complex);
+            string json = schema.SerializeAsJson(OpenApiSpecVersion.OpenApi3_0);
+
+            // Assert
+            Assert.NotNull(json);
+            Assert.Equal(@"{
+  ""title"": ""userSet"",
+  ""type"": ""object"",
+  ""properties"": {
+    ""isBackup"": {
+      ""type"": ""boolean"",
+      ""nullable"": true
+    }
+  },
+  ""discriminator"": {
+    ""propertyName"": ""@odata.type"",
+    ""mapping"": {
+      ""#microsoft.graph.connectedOrganizationMembers"": ""#/components/schemas/microsoft.graph.connectedOrganizationMembers"",
+      ""#microsoft.graph.externalSponsors"": ""#/components/schemas/microsoft.graph.externalSponsors"",
+      ""#microsoft.graph.groupMembers"": ""#/components/schemas/microsoft.graph.groupMembers"",
+      ""#microsoft.graph.internalSponsors"": ""#/components/schemas/microsoft.graph.internalSponsors"",
+      ""#microsoft.graph.requestorManager"": ""#/components/schemas/microsoft.graph.requestorManager"",
+      ""#microsoft.graph.singleUser"": ""#/components/schemas/microsoft.graph.singleUser""
+    }
+  }
+}".ChangeLineBreaks(), json);
+        }
+
         [Fact]
         public void CreateStructuredTypePropertiesSchemaWithCustomAttributeReturnsCorrectSchema()
         {