Add support for JsonPolymorphic and JsonDerivedType attributes. Credits for @schnerring domaindrivendev#2671

Author: Havunen

README.md

@@ -1156,7 +1156,7 @@ services.AddSwaggerGen(c =>
 });
 ```
 
-_NOTE: If you're using the [DotSwashbuckle 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 [DotSwashbuckle Annotations library](#swashbuckleaspnetcoreannotations), it contains a custom selector that's based on the presence of `JsonDerivedType` 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 ####
 
@@ -1222,7 +1222,7 @@ services.AddSwaggerGen(c =>
 });
 ```
 
-_NOTE: If you're using the [DotSwashbuckle 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 [DotSwashbuckle Annotations library](#swashbuckleaspnetcoreannotations), it contains custom selector functions that are based on the presence of `JsonPolymorphic` and `JsonDerivedType` 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)._
 
 ## DotSwashbuckle.AspNetCore.SwaggerUI ##
 
@@ -1505,16 +1505,16 @@ services.AddSwaggerGen(c =>
 });
 
 // Shape.cs
-[SwaggerSubType(typeof(Rectangle))]
-[SwaggerSubType(typeof(Circle))]
+[JsonDerivedType(typeof(Rectangle))]
+[JsonDerivedType(typeof(Circle))]
 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
@@ -1525,12 +1525,21 @@ services.AddSwaggerGen(c =>
 });
 
 // Shape.cs
-[SwaggerDiscriminator("shapeType")]
-[SwaggerSubType(typeof(Rectangle), DiscriminatorValue = "rectangle")]
-[SwaggerSubType(typeof(Circle), DiscriminatorValue = "circle")]
+[JsonPolymorphic(TypeDiscriminatorPropertyName = "shapeType")]
+[JsonDerivedType(typeof(Rectangle), "rectangle")]
+[JsonDerivedType(typeof(Circle), "circle")]
 public abstract class Shape
 {
-    public ShapeType { get; set; }
+    // Avoid using a JsonPolymorphicAttribute.TypeDiscriminatorPropertyName
+    // that conflicts with a property in your type hierarchy.
+    // Related issue: https://github.com/dotnet/runtime/issues/72170
+}
+
+[JsonConverter(typeof(JsonStringEnumConverter))]
+public enum AnimalType
+{
+    Circle,
+    Rectangle
 }
 ```
 

src/DotSwashbuckle.AspNetCore.Annotations/AnnotationsSwaggerGenOptionsExtensions.cs

@@ -1,8 +1,10 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text.Json.Serialization;
 using DotSwashbuckle.AspNetCore.SwaggerGen;
 using DotSwashbuckle.AspNetCore.Annotations;
+using System.Reflection;
 
 namespace Microsoft.Extensions.DependencyInjection
 {
@@ -56,44 +58,27 @@ public static void EnableAnnotations(this SwaggerGenOptions options)
 
         private static IEnumerable<Type> AnnotationsSubTypesSelector(Type type)
         {
-            var subTypeAttributes = type.GetCustomAttributes(false)
-                .OfType<SwaggerSubTypeAttribute>();
+            var jsonDerivedTypeAttributes = type.GetCustomAttributes(false)
+                .OfType<JsonDerivedTypeAttribute>()
+                .ToArray();
 
-            if (subTypeAttributes.Any())
+            if (jsonDerivedTypeAttributes.Any())
             {
-                return subTypeAttributes.Select(attr => attr.SubType);
-            }
-
-            var obsoleteAttribute = type.GetCustomAttributes(false)
-                .OfType<SwaggerSubTypesAttribute>()
-                .FirstOrDefault();
-
-            if (obsoleteAttribute != null)
-            {
-                return obsoleteAttribute.SubTypes;
+                return jsonDerivedTypeAttributes.Select(attr => attr.DerivedType);
             }
 
             return Enumerable.Empty<Type>();
         }
 
         private static string AnnotationsDiscriminatorNameSelector(Type baseType)
         {
-            var discriminatorAttribute = baseType.GetCustomAttributes(false)
-                .OfType<SwaggerDiscriminatorAttribute>()
-                .FirstOrDefault();
-
-            if (discriminatorAttribute != null)
-            {
-                return discriminatorAttribute.PropertyName;
-            }
-
-            var obsoleteAttribute = baseType.GetCustomAttributes(false)
-                .OfType<SwaggerSubTypesAttribute>()
+            var jsonPolymorphicAttribute = baseType.GetCustomAttributes(false)
+                .OfType<JsonPolymorphicAttribute>()
                 .FirstOrDefault();
 
-            if (obsoleteAttribute != null)
+            if (jsonPolymorphicAttribute is not null)
             {
-                return obsoleteAttribute.Discriminator;
+                return jsonPolymorphicAttribute.TypeDiscriminatorPropertyName;
             }
 
             return null;
@@ -104,13 +89,13 @@ private static string AnnotationsDiscriminatorValueSelector(Type subType)
             if (subType.BaseType == null)
                 return null;
 
-            var subTypeAttribute = subType.BaseType.GetCustomAttributes(false)
-                .OfType<SwaggerSubTypeAttribute>()
-                .FirstOrDefault(attr => attr.SubType == subType);
+            var jsonDerivedTypeAttribute = subType.BaseType.GetCustomAttributes(false)
+                .OfType<JsonDerivedTypeAttribute>()
+                .FirstOrDefault(attr => attr.DerivedType == subType);
 
-            if (subTypeAttribute != null)
+            if (jsonDerivedTypeAttribute is not null)
             {
-                return subTypeAttribute.DiscriminatorValue;
+                return jsonDerivedTypeAttribute.TypeDiscriminator?.ToString();
             }
 
             return null;