Added setting UsePolymorphicSerialization

src/Refitter.Core/CSharpClientGeneratorFactory.cs

@@ -1,3 +1,5 @@
+using System.Reflection;
+using NJsonSchema.CodeGeneration;
 using NJsonSchema.CodeGeneration.CSharp;
 
 using NSwag;
@@ -17,30 +19,43 @@ public CustomCSharpClientGenerator Create()
             }
         }
 
+        var csharpClientGeneratorSettings = new CSharpClientGeneratorSettings
+        {
+            GenerateClientClasses = false,
+            GenerateDtoTypes = true,
+            GenerateClientInterfaces = false,
+            GenerateExceptionClasses = false,
+            CodeGeneratorSettings = { PropertyNameGenerator = new CustomCSharpPropertyNameGenerator(), },
+            CSharpGeneratorSettings =
+            {
+                Namespace = settings.ContractsNamespace ?? settings.Namespace,
+                JsonLibrary = CSharpJsonLibrary.SystemTextJson,
+                TypeAccessModifier = settings.TypeAccessibility.ToString().ToLowerInvariant(),
+                ClassStyle =
+                    settings.ImmutableRecords ||
+                    settings.CodeGeneratorSettings?.GenerateNativeRecords is true
+                    ? CSharpClassStyle.Record
+                    : CSharpClassStyle.Poco,
+                GenerateNativeRecords =
+                    settings.ImmutableRecords ||
+                    settings.CodeGeneratorSettings?.GenerateNativeRecords is true,
+            }
+        };
+
+        if (settings.UseSystemTextJsonPolymorphicSerialization)
+        {
+            csharpClientGeneratorSettings.CSharpGeneratorSettings.TemplateFactory = new CustomTemplateFactory(
+                csharpClientGeneratorSettings.CSharpGeneratorSettings,
+                [
+                    typeof(CSharpGenerator).Assembly,
+                    typeof(CSharpGeneratorBaseSettings).Assembly,
+                    typeof(CustomTemplateFactory).Assembly,
+                ]);
+        }
+
         var generator = new CustomCSharpClientGenerator(
             document,
-            new CSharpClientGeneratorSettings
-            {
-                GenerateClientClasses = false,
-                GenerateDtoTypes = true,
-                GenerateClientInterfaces = false,
-                GenerateExceptionClasses = false,
-                CodeGeneratorSettings = { PropertyNameGenerator = new CustomCSharpPropertyNameGenerator(), },
-                CSharpGeneratorSettings =
-                {
-                    Namespace = settings.ContractsNamespace ?? settings.Namespace,
-                    JsonLibrary = CSharpJsonLibrary.SystemTextJson,
-                    TypeAccessModifier = settings.TypeAccessibility.ToString().ToLowerInvariant(),
-                    ClassStyle =
-                        settings.ImmutableRecords ||
-                        settings.CodeGeneratorSettings?.GenerateNativeRecords is true
-                        ? CSharpClassStyle.Record
-                        : CSharpClassStyle.Poco,
-                    GenerateNativeRecords =
-                        settings.ImmutableRecords ||
-                        settings.CodeGeneratorSettings?.GenerateNativeRecords is true,
-                }
-            });
+            csharpClientGeneratorSettings);
 
         MapCSharpGeneratorSettings(
             settings.CodeGeneratorSettings,
@@ -82,4 +97,42 @@ private static void MapCSharpGeneratorSettings(
             settingsProperty.SetValue(destination, value);
         }
     }
-}
+
+    /// <summary>
+    /// custom template factory
+    /// solely for the purpose of supporting UseSystemTextJsonPolymorphicSerialization
+    /// This class and its templates should be removed when NSwag supports this feature.
+    /// </summary>
+    private class CustomTemplateFactory : NSwag.CodeGeneration.DefaultTemplateFactory
+    {
+        /// <summary>Initializes a new instance of the <see cref="DefaultTemplateFactory" /> class.</summary>
+        /// <param name="settings">The settings.</param>
+        /// <param name="assemblies">The assemblies.</param>
+        public CustomTemplateFactory(CodeGeneratorSettingsBase settings, Assembly[] assemblies)
+            : base(settings, assemblies)
+        {
+        }
+
+        /// <summary>Tries to load an embedded Liquid template.</summary>
+        /// <param name="language">The language.</param>
+        /// <param name="template">The template name.</param>
+        /// <returns>The template.</returns>
+        protected override string GetEmbeddedLiquidTemplate(string language, string template)
+        {
+            template = template.TrimEnd('!');
+            var assembly = GetLiquidAssembly("Refitter.Core");
+            var resourceName = $"Refitter.Core.Templates.{template}.liquid";
+
+            var resource = assembly.GetManifestResourceStream(resourceName);
+            if (resource != null)
+            {
+                using (var reader = new StreamReader(resource))
+                {
+                    return reader.ReadToEnd();
+                }
+            }
+
+            return base.GetEmbeddedLiquidTemplate(language, template);
+        }
+    }
+}

src/Refitter.Core/Refitter.Core.csproj

@@ -23,4 +23,8 @@
     </AssemblyAttribute>
   </ItemGroup>
 
+  <ItemGroup>
+    <EmbeddedResource Include="Templates\*.liquid" />
+  </ItemGroup>
+
 </Project>

src/Refitter.Core/Settings/RefitGeneratorSettings.cs

@@ -1,4 +1,4 @@
-using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.CodeAnalysis;
 using System.Text.Json.Serialization;
 
 namespace Refitter.Core;
@@ -216,4 +216,10 @@ public class RefitGeneratorSettings
     /// Dependency Injection is written to a file called DependencyInjection.cs
     /// </summary>
     public bool GenerateMultipleFiles { get; set; }
-}
+
+    /// <summary>
+    /// Set to <c>true</c> to use System.Text.Json polymorphic serialization. Default is <c>false</c>
+    /// Gets a value indicating whether to use System.Text.Json polymorphic serialization
+    /// </summary>
+    public bool UseSystemTextJsonPolymorphicSerialization { get; set; }
+}

src/Refitter.Core/Templates/Class.liquid

@@ -0,0 +1,148 @@
+{%- if HasDescription -%}
+/// <summary>
+/// {{ Description | csharpdocs }}
+/// </summary>
+{%- endif -%}
+{%- if HasDiscriminator -%}
+{%- if UseSystemTextJson -%}
+[System.Text.Json.Serialization.JsonPolymorphic(TypeDiscriminatorPropertyName = "{{ Discriminator }}", UnknownDerivedTypeHandling = JsonUnknownDerivedTypeHandling.FallBackToBaseType)]
+{%- else -%}
+[Newtonsoft.Json.JsonConverter(typeof(JsonInheritanceConverter), "{{ Discriminator }}")]
+{%- endif -%}
+{%- for derivedClass in DerivedClasses -%}
+{%- if derivedClass.IsAbstract != true -%}
+{%- if UseSystemTextJson -%}
+[System.Text.Json.Serialization.JsonDerivedType(typeof({{ derivedClass.ClassName }}), typeDiscriminator: "{{ derivedClass.Discriminator }}")]
+{%- endif -%}
+{%- endif -%}
+{%- endfor -%}
+{%- endif -%}
+[System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "{{ ToolchainVersion }}")]
+{%- if InheritsExceptionSchema -%}
+{%-   if UseSystemTextJson -%}
+// TODO(system.text.json): What to do here?
+{%-   else -%}
+[Newtonsoft.Json.JsonObjectAttribute]
+{%-   endif -%}
+{%- endif -%}
+{%- if IsDeprecated -%}
+[System.Obsolete{% if HasDeprecatedMessage %}({{ DeprecatedMessage | literal }}){% endif %}]
+{% endif -%}
+{%- template Class.Annotations -%}
+{{ TypeAccessModifier }} {% if IsAbstract %}abstract {% endif %}partial {% if GenerateNativeRecords %}record{% else %}class{% endif %} {{ClassName}} {%- template Class.Inheritance %}
+{
+{%- if IsTuple -%}
+    public {{ ClassName }}({%- for tupleType in TupleTypes %}{{ tupleType }} item{{ forloop.index }}{%- if forloop.last == false %}, {% endif %}{% endfor %}) : base({%- for tupleType in TupleTypes %}item{{ forloop.index }}{%- if forloop.last == false %}, {% endif %}{% endfor %})
+    {
+    }
+
+{%- endif -%}
+{%- if RenderInpc or RenderPrism -%}
+{%- for property in Properties -%}
+    private {{ property.Type }} {{ property.FieldName }}{%- if property.HasDefaultValue %} = {{ property.DefaultValue }}{% elsif GenerateNullableReferenceTypes %} = default!{%- endif %};
+{%- endfor -%}
+
+{%- endif -%}
+    {%- template Class.Constructor -%}
+{%- if RenderRecord -%}
+    {% template Class.Constructor.Record -%}
+{%- endif -%}
+{%- for property in Properties -%}
+{%-   if property.HasDescription -%}
+    /// <summary>
+    /// {{ property.Description | csharpdocs }}
+    /// </summary>
+{%-   endif -%}
+{%- if UseSystemTextJson %}
+    [System.Text.Json.Serialization.JsonPropertyName("{{ property.Name }}")]
+{%-   if property.IsStringEnumArray %}
+    // TODO(system.text.json): Add string enum item converter
+{%-   endif -%}
+{%- else -%}
+    [Newtonsoft.Json.JsonProperty("{{ property.Name }}", Required = {{ property.JsonPropertyRequiredCode }}{% if property.IsStringEnumArray %}, ItemConverterType = typeof(Newtonsoft.Json.Converters.StringEnumConverter){% endif %})]
+{%- endif -%}
+{%-   if property.RenderRequiredAttribute -%}
+    [System.ComponentModel.DataAnnotations.Required{% if property.AllowEmptyStrings %}(AllowEmptyStrings = true){% endif %}]
+{%-   endif -%}
+{%-   if property.RenderRangeAttribute -%}
+    [System.ComponentModel.DataAnnotations.Range({{ property.RangeMinimumValue }}, {{ property.RangeMaximumValue }})]
+{%-   endif -%}
+{%-   if property.RenderStringLengthAttribute -%}
+    [System.ComponentModel.DataAnnotations.StringLength({{ property.StringLengthMaximumValue }}{% if property.StringLengthMinimumValue > 0 %}, MinimumLength = {{ property.StringLengthMinimumValue }}{% endif %})]
+{%-   endif -%}
+{%-   if property.RenderMinLengthAttribute -%}
+    [System.ComponentModel.DataAnnotations.MinLength({{ property.MinLengthAttribute }})]
+{%-   endif -%}
+{%-   if property.RenderMaxLengthAttribute -%}
+    [System.ComponentModel.DataAnnotations.MaxLength({{ property.MaxLengthAttribute }})]
+{%-   endif -%}
+{%-   if property.RenderRegularExpressionAttribute -%}
+    [System.ComponentModel.DataAnnotations.RegularExpression(@"{{ property.RegularExpressionValue }}")]
+{%-   endif -%}
+{%-   if property.IsStringEnum -%}
+{%-     if UseSystemTextJson -%}
+    [System.Text.Json.Serialization.JsonConverter(typeof(System.Text.Json.Serialization.JsonStringEnumConverter))]
+{%-     else -%}
+    [Newtonsoft.Json.JsonConverter(typeof(Newtonsoft.Json.Converters.StringEnumConverter))]
+{%-     endif -%}
+{%-  endif -%}
+{%-   if property.IsDate and UseDateFormatConverter -%}
+{%-     if UseSystemTextJson -%}
+    [System.Text.Json.Serialization.JsonConverter(typeof(DateFormatConverter))]
+{%-     else -%}
+    [Newtonsoft.Json.JsonConverter(typeof(DateFormatConverter))]
+{%-     endif -%}
+{%-   endif -%}
+{%-   if property.IsDeprecated -%}
+    [System.Obsolete{% if property.HasDeprecatedMessage %}({{ property.DeprecatedMessage | literal }}){% endif %}]
+{%-   endif -%}
+    {%- template Class.Property.Annotations -%}
+    public {{ property.Type }} {{ property.PropertyName }}{% if RenderInpc == false and RenderPrism == false %} { get; {% if property.HasSetter and RenderRecord == false %}set; {% elsif RenderRecord and GenerateNativeRecords %}init; {% endif %}}{% if property.HasDefaultValue and RenderRecord == false %} = {{ property.DefaultValue }};{% elsif GenerateNullableReferenceTypes and RenderRecord == false %} = default!;{% endif %}
+{% else %}
+    {
+        get { return {{ property.FieldName }}; }
+
+{%-     if property.HasSetter -%}
+{%-         if RenderInpc -%}
+        {{PropertySetterAccessModifier}}set
+        {
+            if ({{ property.FieldName }} != value)
+            {
+                {{ property.FieldName }} = value;
+                RaisePropertyChanged();
+            }
+        }
+{%-         else -%}
+        {{PropertySetterAccessModifier}}set { SetProperty(ref {{ property.FieldName }}, value); }
+{%-         endif -%}
+{%-     endif -%}
+    }
+{%-   endif %}
+{%- endfor -%}
+
+{%- if GenerateAdditionalPropertiesProperty -%}
+
+    private System.Collections.Generic.IDictionary<string, {{ AdditionalPropertiesType }}>{% if GenerateNullableReferenceTypes %}?{% endif %} _additionalProperties;
+
+{%-       if UseSystemTextJson -%}
+    [System.Text.Json.Serialization.JsonExtensionData]
+{%-       else -%}
+    [Newtonsoft.Json.JsonExtensionData]
+{%-       endif -%}
+    public System.Collections.Generic.IDictionary<string, {{ AdditionalPropertiesType }}> AdditionalProperties
+    {
+        get { return _additionalProperties ?? (_additionalProperties = new System.Collections.Generic.Dictionary<string, {{ AdditionalPropertiesType }}>()); }
+        {{PropertySetterAccessModifier}}set { _additionalProperties = value; }
+    }
+
+{%- endif -%}
+{%- if GenerateJsonMethods -%}
+    {% template Class.ToJson %}
+    {% template Class.FromJson %}
+
+{%- endif -%}
+{%- if RenderInpc -%}
+    {% template Class.Inpc %}
+{%- endif -%}
+    {% template Class.Body %}
+}