Add support for STJ-native C# code gen

src/NJsonSchema.CodeGeneration.CSharp.Tests/InheritanceInterfaceTests.cs

@@ -80,5 +80,27 @@ public async Task When_schema_has_base_schema_then_it_is_referenced_with_STJ()
             Assert.Contains("[JsonInheritanceAttribute(\"Banana\", typeof(Banana))]", code);
             Assert.Contains("public class JsonInheritanceConverter<TBase> : System.Text.Json.Serialization.JsonConverter<TBase>", code);
         }
+
+        [Fact]
+        public async Task When_using_STJ_polymorphic_serialization_then_NSwag_inheritance_converter_and_attributes_are_not_generated()
+        {
+            //// Arrange
+            var json = JsonSchema.FromType<MyContainer>();
+            var data = json.ToJson();
+
+            var generator = new CSharpGenerator(json, new CSharpGeneratorSettings
+            {
+                JsonLibrary = CSharpJsonLibrary.SystemTextJson,
+                JsonPolymorphicSerializationStyle = CSharpJsonPolymorphicSerializationStyle.SystemTextJson
+            });
+
+            //// Act
+            var code = generator.GenerateFile();
+
+            //// Assert
+            Assert.DoesNotContain("[JsonInheritanceConverter", code);
+            Assert.DoesNotContain("[JsonInheritanceAttribute", code);
+            Assert.DoesNotContain("public class JsonInheritanceConverter", code);
+        }
     }
 }

src/NJsonSchema.CodeGeneration.CSharp.Tests/InheritanceTests.cs

@@ -156,6 +156,33 @@ public async Task When_definitions_inherit_from_root_schema()
             Assert.Contains("[JsonInheritanceAttribute(\"PersianCat\", typeof(PersianCat))]", code);
         }
 
+        [Fact]
+        public async Task When_definitions_inherit_from_root_schema_and_STJ_polymorphism()
+        {
+            //// Arrange
+            var path = GetTestDirectory() + "/References/Animal.json";
+
+            //// Act
+            var schema = await JsonSchema.FromFileAsync(path);
+            var generator = new CSharpGenerator(schema, new CSharpGeneratorSettings
+            {
+                ClassStyle = CSharpClassStyle.Record,
+                JsonLibrary = CSharpJsonLibrary.SystemTextJson,
+                JsonPolymorphicSerializationStyle = CSharpJsonPolymorphicSerializationStyle.SystemTextJson
+            });
+
+            //// Act
+            var code = generator.GenerateFile();
+
+            //// Assert
+            Assert.Contains("public abstract partial class Animal", code);
+            Assert.Contains("public partial class Cat : Animal", code);
+            Assert.Contains("public partial class PersianCat : Cat", code);
+            Assert.Contains("[System.Text.Json.Serialization.JsonPolymorphic(TypeDiscriminatorPropertyName = \"discriminator\")]", code);
+            Assert.Contains("[System.Text.Json.Serialization.JsonDerivedType(typeof(Cat), typeDiscriminator: \"Cat\")]", code);
+            Assert.Contains("[System.Text.Json.Serialization.JsonDerivedType(typeof(PersianCat), typeDiscriminator: \"PersianCat\")]", code);
+        }
+
         private string GetTestDirectory()
         {
             var codeBase = Assembly.GetExecutingAssembly().CodeBase;

src/NJsonSchema.CodeGeneration.CSharp/CSharpGeneratorSettings.cs

@@ -39,6 +39,7 @@ public CSharpGeneratorSettings()
 
             ClassStyle = CSharpClassStyle.Poco;
             JsonLibrary = CSharpJsonLibrary.NewtonsoftJson;
+            JsonPolymorphicSerializationStyle = CSharpJsonPolymorphicSerializationStyle.NJsonSchema;
 
             RequiredPropertiesMustBeDefined = true;
             GenerateDataAnnotations = true;
@@ -120,6 +121,9 @@ public CSharpGeneratorSettings()
         /// <summary>Gets or sets the CSharp JSON library to use (default: 'NewtonsoftJson', 'SystemTextJson' is experimental/not complete).</summary>
         public CSharpJsonLibrary JsonLibrary { get; set; }
 
+        /// <summary>Gets or sets the CSharp JSON polymorphic serialization style (default: 'NSwag', 'SystemTextJson' is experimental/not complete).</summary>
+        public CSharpJsonPolymorphicSerializationStyle JsonPolymorphicSerializationStyle { get; set; }
+
         /// <summary>Gets or sets the access modifier of generated classes and interfaces (default: 'public').</summary>
         public string TypeAccessModifier { get; set; }
 

src/NJsonSchema.CodeGeneration.CSharp/CSharpJsonPolymorphicSerializationStyle.cs

@@ -0,0 +1,12 @@
+namespace NJsonSchema.CodeGeneration.CSharp
+{
+    /// <summary>The CSharp JSON polymorphic serialization style.</summary>
+    public enum CSharpJsonPolymorphicSerializationStyle
+    {
+        /// <summary>Use NJsonSchema polymorphic serialization</summary>
+        NJsonSchema, 
+
+        /// <summary>Use System.Text.Json polymorphic serialization</summary>
+        SystemTextJson
+    }
+}

src/NJsonSchema.CodeGeneration.CSharp/Models/ClassTemplateModel.cs

@@ -53,6 +53,9 @@ public ClassTemplateModel(string typeName, CSharpGeneratorSettings settings,
         /// <summary>Gets a value indicating whether to use System.Text.Json</summary>
         public bool UseSystemTextJson => _settings.JsonLibrary == CSharpJsonLibrary.SystemTextJson;
 
+        /// <summary>Gets a value indicating whether to use System.Text.Json polymorphic serialization</summary>
+        public bool UseSystemTextJsonPolymorphicSerialization => _settings.JsonPolymorphicSerializationStyle == CSharpJsonPolymorphicSerializationStyle.SystemTextJson;
+
         /// <summary>Gets or sets the class name.</summary>
         public override string ClassName { get; }
 

src/NJsonSchema.CodeGeneration.CSharp/Models/JsonInheritanceConverterTemplateModel.cs

@@ -21,5 +21,8 @@ public JsonInheritanceConverterTemplateModel(CSharpGeneratorSettings settings)
 
         /// <summary>Gets a value indicating whether to use System.Text.Json</summary>
         public bool UseSystemTextJson => _settings.JsonLibrary == CSharpJsonLibrary.SystemTextJson;
+
+        /// <summary>Gets a value indicating whether to use System.Text.Json polymorphic serialization</summary>
+        public bool UseSystemTextJsonPolymorphicSerialization => _settings.JsonPolymorphicSerializationStyle == CSharpJsonPolymorphicSerializationStyle.SystemTextJson;
     }
 }

src/NJsonSchema.CodeGeneration.CSharp/Templates/Class.liquid

@@ -5,14 +5,22 @@
 {%- endif -%}
 {%- if HasDiscriminator -%}
 {%- if UseSystemTextJson -%}
+{%- if UseSystemTextJsonPolymorphicSerialization -%}
+[System.Text.Json.Serialization.JsonPolymorphic(TypeDiscriminatorPropertyName = "{{ Discriminator }}")]
+{%- else -%}
 [JsonInheritanceConverter(typeof({{ ClassName }}), "{{ Discriminator }}")]
+{%- endif -%}
 {%- else -%}
 [Newtonsoft.Json.JsonConverter(typeof(JsonInheritanceConverter), "{{ Discriminator }}")]
 {%- endif -%}
 {%- for derivedClass in DerivedClasses -%}
 {%- if derivedClass.IsAbstract != true -%}
+{%- if UseSystemTextJson and UseSystemTextJsonPolymorphicSerialization -%}
+[System.Text.Json.Serialization.JsonDerivedType(typeof({{ derivedClass.ClassName }}), typeDiscriminator: "{{ derivedClass.Discriminator }}")]
+{%- else -%}
 [JsonInheritanceAttribute("{{ derivedClass.Discriminator }}", typeof({{ derivedClass.ClassName }}))]
 {%- endif -%}
+{%- endif -%}
 {%- endfor -%}
 {%- endif -%}
 [System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "{{ ToolchainVersion }}")]

src/NJsonSchema.CodeGeneration.CSharp/Templates/JsonInheritanceAttribute.liquid

@@ -1,4 +1,5 @@
-[System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "{{ ToolchainVersion }}")]
+{%- if UseSystemTextJsonPolymorphicSerialization == false -%}
+[System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "{{ ToolchainVersion }}")]
 [System.AttributeUsage(System.AttributeTargets.Class | System.AttributeTargets.Interface, AllowMultiple = true)]
 internal class JsonInheritanceAttribute : System.Attribute
 {
@@ -11,4 +12,5 @@ internal class JsonInheritanceAttribute : System.Attribute
     public string Key { get; }
 
     public System.Type Type { get; }
-}
+}
+{%- endif -%}

src/NJsonSchema.CodeGeneration.CSharp/Templates/JsonInheritanceConverter.liquid

@@ -1,4 +1,5 @@
-[System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "{{ ToolchainVersion }}")]
+{%- if UseSystemTextJsonPolymorphicSerialization == false -%}
+[System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "{{ ToolchainVersion }}")]
 {%- if UseSystemTextJson -%}
 internal class JsonInheritanceConverterAttribute : System.Text.Json.Serialization.JsonConverterAttribute
 {
@@ -236,3 +237,4 @@ public class JsonInheritanceConverter : Newtonsoft.Json.JsonConverter
     }
 }
 {%- endif -%}
+{%- endif -%}