Add support for JsonPolymorphic and JsonDerivedType attributes to Swashbuckle.AspNetCore.Annotations for .NET7 and later

README.md

@@ -1134,7 +1134,7 @@ services.AddSwaggerGen(c =>
 });
 ```
 
-_NOTE: If you're using the [Swashbuckle Annotations library](#swashbuckleaspnetcoreannotations), it contains a custom selector that's based on the presence of `SwaggerSubType` attributes on base class definitions. This way, you can use simple attributes to explicitly list the inheritance and/or polymorphism relationships you want to expose. To enable this behavior, check out the [Annotations docs](#list-known-subtypes-for-inheritance-and-polymorphism)._
+_NOTE: If you're using the [Swashbuckle Annotations library](#swashbuckleaspnetcoreannotations), it contains a custom selector that's based on the presence of `JsonDerivedType` (or `SwaggerSubType` for .NET 6 or earlier) attributes on base class definitions. This way, you can use simple attributes to explicitly list the inheritance and/or polymorphism relationships you want to expose. To enable this behavior, check out the [Annotations docs](#list-known-subtypes-for-inheritance-and-polymorphism)._
 
 #### Describing Discriminators ####
 
@@ -1200,7 +1200,7 @@ services.AddSwaggerGen(c =>
 });
 ```
 
-_NOTE: If you're using the [Swashbuckle Annotations library](#swashbuckleaspnetcoreannotations), it contains custom selector functions that are based on the presence of `SwaggerDiscriminator` and `SwaggerSubType` attributes on base class definitions. This way, you can use simple attributes to explicitly provide discriminator metadata. To enable this behavior, check out the [Annotations docs](#enrich-polymorphic-base-classes-with-discriminator-metadata)._
+_NOTE: If you're using the [Swashbuckle Annotations library](#swashbuckleaspnetcoreannotations), it contains custom selector functions that are based on the presence of `JsonPolymorphic` (or `SwaggerDiscriminator` for .NET 6 or earlier) and `JsonDerivedType` (or `SwaggerSubType` for .NET 6 or earlier) attributes on base class definitions. This way, you can use simple attributes to explicitly provide discriminator metadata. To enable this behavior, check out the [Annotations docs](#enrich-polymorphic-base-classes-with-discriminator-metadata)._
 
 ## Swashbuckle.AspNetCore.SwaggerUI ##
 
@@ -1483,6 +1483,15 @@ services.AddSwaggerGen(c =>
 });
 
 // Shape.cs
+
+// .NET 7 or later
+[JsonDerivedType(typeof(Rectangle))]
+[JsonDerivedType(typeof(Circle))]
+public abstract class Shape
+{
+}
+
+// .NET 6 or earlier
 [SwaggerSubType(typeof(Rectangle))]
 [SwaggerSubType(typeof(Circle))]
 public abstract class Shape
@@ -1492,7 +1501,7 @@ public abstract class Shape
 
 ### Enrich Polymorphic Base Classes with Discriminator Metadata ###
 
-If you're using annotations to _explicitly_ indicate the "known" subtypes for a polymorphic base type, you can combine the `SwaggerDiscriminatorAttribute` with the `SwaggerSubTypeAttribute` to provide additional metadata about the "discriminator" property, which will then be incorporated into the generated schema definition:
+If you're using annotations to _explicitly_ indicate the "known" subtypes for a polymorphic base type, you can combine the `JsonPolymorphicAttribute` with the `JsonDerivedTypeAttribute` to provide additional metadata about the "discriminator" property, which will then be incorporated into the generated schema definition:
 
 
 ```csharp
@@ -1503,12 +1512,32 @@ services.AddSwaggerGen(c =>
 });
 
 // Shape.cs
+
+// .NET 7 or later
+[JsonPolymorphic(TypeDiscriminatorPropertyName = "shapeType")]
+[JsonDerivedType(typeof(Rectangle), "rectangle")]
+[JsonDerivedType(typeof(Circle), "circle")]
+public abstract class Shape
+{
+    // Avoid using a JsonPolymorphicAttribute.TypeDiscriminatorPropertyName
+    // that conflicts with a property in your type hierarchy.
+    // Related issue: https://github.com/dotnet/runtime/issues/72170
+}
+
+// .NET 6 or earlier
 [SwaggerDiscriminator("shapeType")]
 [SwaggerSubType(typeof(Rectangle), DiscriminatorValue = "rectangle")]
 [SwaggerSubType(typeof(Circle), DiscriminatorValue = "circle")]
 public abstract class Shape
 {
-    public ShapeType { get; set; }
+    public ShapeType ShapeType { get; set; }
+}
+
+[JsonConverter(typeof(JsonStringEnumConverter))]
+public enum AnimalType
+{
+    Circle,
+    Rectangle
 }
 ```
 

src/Swashbuckle.AspNetCore.Annotations/AnnotationsSwaggerGenOptionsExtensions.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text.Json.Serialization;
 using Swashbuckle.AspNetCore.SwaggerGen;
 using Swashbuckle.AspNetCore.Annotations;
 
@@ -56,8 +57,20 @@ public static void EnableAnnotations(this SwaggerGenOptions options)
 
         private static IEnumerable<Type> AnnotationsSubTypesSelector(Type type)
         {
+#if NET7_0_OR_GREATER
+            var jsonDerivedTypeAttributes = type.GetCustomAttributes(false)
+                .OfType<JsonDerivedTypeAttribute>()
+                .ToArray();
+
+            if (jsonDerivedTypeAttributes.Any())
+            {
+                return jsonDerivedTypeAttributes.Select(attr => attr.DerivedType);
+            }
+#endif
+
             var subTypeAttributes = type.GetCustomAttributes(false)
-                .OfType<SwaggerSubTypeAttribute>();
+                .OfType<SwaggerSubTypeAttribute>()
+                .ToArray();
 
             if (subTypeAttributes.Any())
             {
@@ -78,6 +91,17 @@ private static IEnumerable<Type> AnnotationsSubTypesSelector(Type type)
 
         private static string AnnotationsDiscriminatorNameSelector(Type baseType)
         {
+#if NET7_0_OR_GREATER
+            var jsonPolymorphicAttribute = baseType.GetCustomAttributes(false)
+                .OfType<JsonPolymorphicAttribute>()
+                .FirstOrDefault();
+
+            if (jsonPolymorphicAttribute is not null)
+            {
+                return jsonPolymorphicAttribute.TypeDiscriminatorPropertyName;
+            }
+#endif
+
             var discriminatorAttribute = baseType.GetCustomAttributes(false)
                 .OfType<SwaggerDiscriminatorAttribute>()
                 .FirstOrDefault();
@@ -104,6 +128,17 @@ private static string AnnotationsDiscriminatorValueSelector(Type subType)
             if (subType.BaseType == null)
                 return null;
 
+#if NET7_0_OR_GREATER
+            var jsonDerivedTypeAttribute = subType.BaseType.GetCustomAttributes(false)
+                .OfType<JsonDerivedTypeAttribute>()
+                .FirstOrDefault(attr => attr.DerivedType == subType);
+
+            if (jsonDerivedTypeAttribute is not null)
+            {
+                return jsonDerivedTypeAttribute.TypeDiscriminator?.ToString();
+            }
+#endif
+
             var subTypeAttribute = subType.BaseType.GetCustomAttributes(false)
                 .OfType<SwaggerSubTypeAttribute>()
                 .FirstOrDefault(attr => attr.SubType == subType);

src/Swashbuckle.AspNetCore.Annotations/SwaggerDiscriminatorAttribute.cs

@@ -2,6 +2,9 @@
 
 namespace Swashbuckle.AspNetCore.Annotations
 {
+#if NET7_0_OR_GREATER
+    [Obsolete("Use JsonPolymorphic attribute instead")]
+#endif
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Interface, AllowMultiple = false)]
     public class SwaggerDiscriminatorAttribute : Attribute
     {

src/Swashbuckle.AspNetCore.Annotations/SwaggerSubTypeAttribute.cs

@@ -2,6 +2,9 @@
 
 namespace Swashbuckle.AspNetCore.Annotations
 {
+#if NET7_0_OR_GREATER
+    [Obsolete("Use JsonDerivedType attribute instead")]
+#endif
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Interface, AllowMultiple = true)]
     public class SwaggerSubTypeAttribute : Attribute
     {

test/WebSites/NswagClientExample/Controllers/AnimalsController.cs

@@ -17,9 +17,10 @@ public void CreateAnimal([Required]Animal animal)
         }
     }
 
-    [SwaggerDiscriminator("animalType")]
-    [SwaggerSubType(typeof(Cat), DiscriminatorValue = "Cat")]
-    [SwaggerSubType(typeof(Dog), DiscriminatorValue = "Dog")]
+
+    [JsonPolymorphic(TypeDiscriminatorPropertyName = "animalType")]
+    [JsonDerivedType(typeof(Cat), "Cat")]
+    [JsonDerivedType(typeof(Dog), "Dog")]
     public class Animal
     {
         public AnimalType AnimalType { get; set; }

test/WebSites/NswagClientExample/NswagClientExample.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFramework>net7.0</TargetFramework>
     <DotNetSwaggerPath>$([System.IO.Path]::Combine("..", "..", "..", "src", "Swashbuckle.AspNetCore.Cli", "bin", $(Configuration), $(TargetFramework), "dotnet-swagger.dll"))</DotNetSwaggerPath>
   </PropertyGroup>