Fix supporting System.Text.Json in CSharpJsonSerializerGenerator

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

@@ -0,0 +1,85 @@
+using System;
+using Xunit;
+
+namespace NJsonSchema.CodeGeneration.CSharp.Tests
+{
+    public class CSharpJsonSerializerGeneratorTests
+    {
+        [Fact]
+        public void When_using_SytemTextJson_with_JsonConverters_GenerateJsonSerializerParameterCode_generates_correctly()
+        {
+            //// Arrange
+            var additionalJsonConverters = new string[] { "AdditionalConverter1", "AdditionalConverter2" };
+            var settings = new CSharpGeneratorSettings
+            {
+                JsonLibrary = CSharpJsonLibrary.SystemTextJson,
+                JsonConverters = new string[] { "CustomConverter1", "CustomConverter2" }
+            };
+
+            //// Act
+            var output = CSharpJsonSerializerGenerator.GenerateJsonSerializerParameterCode(settings, additionalJsonConverters);
+            Console.WriteLine(output);
+
+            //// Assert
+            Assert.Equal(", System.Text.Json.JsonSerializerOptions(); var converters = new System.Text.Json.Serialization.JsonConverter[] { new CustomConverter1(), new CustomConverter2(), new AdditionalConverter1(), new AdditionalConverter2() }", output);
+        }
+
+        [Fact]
+        public void When_using_NewtonsoftJson_with_JsonConverters_GenerateJsonSerializerParameterCode_generates_correctly()
+        {
+            //// Arrange
+            var additionalJsonConverters = new string[] { "AdditionalConverter1", "AdditionalConverter2" };
+            var settings = new CSharpGeneratorSettings
+            {
+                JsonLibrary = CSharpJsonLibrary.NewtonsoftJson,
+                JsonConverters = new string[] { "CustomConverter1", "CustomConverter2" }
+            };
+
+            //// Act
+            var output = CSharpJsonSerializerGenerator.GenerateJsonSerializerParameterCode(settings, additionalJsonConverters);
+            Console.WriteLine(output);
+
+            //// Assert
+            Assert.Equal(", new Newtonsoft.Json.JsonConverter[] { new CustomConverter1(), new CustomConverter2(), new AdditionalConverter1(), new AdditionalConverter2() }", output);
+        }
+
+        [Fact]
+        public void When_using_SytemTextJson_with_JsonSerializerSettingsOrOptionsTransformationMethod_GenerateJsonSerializerParameterCode_generates_correctly()
+        {
+            //// Arrange
+            var settings = new CSharpGeneratorSettings
+            {
+                JsonLibrary = CSharpJsonLibrary.SystemTextJson,
+                JsonSerializerSettingsTransformationMethod = "TestJsonSerializerSettingsTransformationMethod"
+            };
+
+            //// Act
+            var output = CSharpJsonSerializerGenerator.GenerateJsonSerializerParameterCode(settings, null);
+            Console.WriteLine(output);
+
+            //// Assert
+            Assert.Equal(", TestJsonSerializerSettingsTransformationMethod(System.Text.Json.JsonSerializerOptions())", output);
+        }
+
+        [Fact]
+        public void When_using_NewtonsoftJson_with_HandleReferences_and_JsonConverters_and_JsonSerializerSettingsTransformationMethod_GenerateJsonSerializerParameterCode_generates_correctly()
+        {
+            //// Arrange
+            var additionalJsonConverters = new string[] { "AdditionalConverter1", "AdditionalConverter2" };
+            var settings = new CSharpGeneratorSettings
+            {
+                JsonLibrary = CSharpJsonLibrary.NewtonsoftJson,
+                HandleReferences = true,
+                JsonConverters = new string[] { "CustomConverter1", "CustomConverter2" },
+                JsonSerializerSettingsTransformationMethod = "TestJsonSerializerSettingsTransformationMethod",
+            };
+
+            //// Act
+            var output = CSharpJsonSerializerGenerator.GenerateJsonSerializerParameterCode(settings, additionalJsonConverters);
+            Console.WriteLine(output);
+
+            //// Assert
+            Assert.Equal(", TestJsonSerializerSettingsTransformationMethod(new Newtonsoft.Json.JsonSerializerSettings { PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.All, Converters = new Newtonsoft.Json.JsonConverter[] { new CustomConverter1(), new CustomConverter2(), new AdditionalConverter1(), new AdditionalConverter2() } })", output);
+        }
+    }
+}

src/NJsonSchema.CodeGeneration.CSharp/CSharpGeneratorSettings.cs

@@ -57,7 +57,7 @@ public CSharpGeneratorSettings()
         /// <summary>Gets or sets the .NET namespace of the generated types (default: MyNamespace).</summary>
         public string Namespace { get; set; }
 
-        /// <summary>Gets or sets a value indicating whether a required property must be defined in JSON 
+        /// <summary>Gets or sets a value indicating whether a required property must be defined in JSON
         /// (sets Required.Always when the property is required) (default: true).</summary>
         public bool RequiredPropertiesMustBeDefined { get; set; }
 
@@ -121,7 +121,7 @@ public CSharpGeneratorSettings()
         /// <summary>Gets or sets a value indicating whether to use preserve references handling (All) in the JSON serializer (default: false).</summary>
         public bool HandleReferences { get; set; }
 
-        /// <summary>Gets or sets the name of a static method which is called to transform the JsonSerializerSettings used in the generated ToJson()/FromJson() methods (default: null).</summary>
+        /// <summary>Gets or sets the name of a static method which is called to transform the JsonSerializerSettings (for Newtonsoft.Json) or the JsonSerializerOptions (for System.Text.Json) used in the generated ToJson()/FromJson() methods (default: null).</summary>
         public string JsonSerializerSettingsTransformationMethod { get; set; }
 
         /// <summary>Gets or sets a value indicating whether to render ToJson() and FromJson() methods (default: true).</summary>

src/NJsonSchema.CodeGeneration.CSharp/CSharpJsonSerializerGenerator.cs

@@ -23,47 +23,78 @@ public static string GenerateJsonSerializerParameterCode(CSharpGeneratorSettings
             var jsonConverters = (settings.JsonConverters ?? new string[0]).Concat(additionalJsonConverters ?? new string[0]).ToList();
             var hasJsonConverters = jsonConverters.Any();
 
-            var useSettingsTransformationMethod = !string.IsNullOrEmpty(settings.JsonSerializerSettingsTransformationMethod);
-            return settings.JsonLibrary == CSharpJsonLibrary.SystemTextJson ?
-                string.Empty : // TODO(system.text.json): What to do here?
-                GenerateForNewtonsoftJson(settings, jsonConverters, hasJsonConverters, useSettingsTransformationMethod);
+            return GenerateForJsonLibrary(settings, jsonConverters, hasJsonConverters);
         }
 
-        private static string GenerateForNewtonsoftJson(CSharpGeneratorSettings settings, List<string> jsonConverters, bool hasJsonConverters, bool useSettingsTransformationMethod)
+        private static string GenerateForJsonLibrary(CSharpGeneratorSettings settings, List<string> jsonConverters, bool hasJsonConverters)
         {
-            if (settings.HandleReferences || useSettingsTransformationMethod)
-            {
-                // TODO(system.text.json): Also support System.Text.Json
-                return ", " +
-                       (useSettingsTransformationMethod ? settings.JsonSerializerSettingsTransformationMethod + "(" : string.Empty) +
-                       "new Newtonsoft.Json.JsonSerializerSettings { " +
-                       (settings.HandleReferences
-                           ? "PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.All"
-                           : string.Empty) +
-                       (hasJsonConverters
-                           ? (settings.HandleReferences ? ", " : string.Empty) + "Converters = " + GenerateConverters(jsonConverters)
-                           : string.Empty) +
-                       " }" +
-                       (useSettingsTransformationMethod ? ")" : string.Empty);
-            }
-            else
+            var useSettingsTransformationMethod = !string.IsNullOrEmpty(settings.JsonSerializerSettingsTransformationMethod);
+            switch (settings.JsonLibrary)
             {
-                if (hasJsonConverters)
-                {
-                    return ", " + GenerateConverters(jsonConverters);
-                }
-                else
-                {
+                case CSharpJsonLibrary.NewtonsoftJson:
+                    if (settings.HandleReferences || useSettingsTransformationMethod)
+                    {
+                        return ", " +
+                            (useSettingsTransformationMethod ? settings.JsonSerializerSettingsTransformationMethod + "(" : string.Empty) +
+                            "new Newtonsoft.Json.JsonSerializerSettings { " +
+                            (settings.HandleReferences
+                                ? "PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.All"
+                                : string.Empty) +
+                            (hasJsonConverters
+                                ? (settings.HandleReferences ? ", " : string.Empty) + "Converters = " + GenerateConverters(jsonConverters, settings.JsonLibrary)
+                                : string.Empty) +
+                            " }" +
+                            (useSettingsTransformationMethod ? ")" : string.Empty);
+                    }
+                    else
+                    {
+                        if (hasJsonConverters)
+                        {
+                            return ", " + GenerateConverters(jsonConverters, settings.JsonLibrary);
+                        }
+                        else
+                        {
+                            return string.Empty;
+                        }
+                    }
+
+                case CSharpJsonLibrary.SystemTextJson:
+                    // TODO: add more conditions?
+                    if (useSettingsTransformationMethod || hasJsonConverters)
+                    {
+                        return ", " +
+                            (useSettingsTransformationMethod ? settings.JsonSerializerSettingsTransformationMethod + "(" : string.Empty) +
+                            "System.Text.Json.JsonSerializerOptions()" +
+                            (useSettingsTransformationMethod ? ")" : string.Empty) +
+                            (hasJsonConverters
+                                ? "; var converters = " + GenerateConverters(jsonConverters, settings.JsonLibrary)
+                                : string.Empty);
+                    }
+                    else
+                    {
+                        return string.Empty;
+                    }
+
+                default: // TODO: possibly add more json converters
                     return string.Empty;
-                }
             }
         }
 
-        private static string GenerateConverters(List<string> jsonConverters)
+        private static string GenerateConverters(List<string> jsonConverters, CSharpJsonLibrary jsonLibrary)
         {
             if (jsonConverters.Any())
             {
-                return "new Newtonsoft.Json.JsonConverter[] { " + string.Join(", ", jsonConverters.Select(c => "new " + c + "()")) + " }";
+                switch (jsonLibrary)
+                {
+                    case CSharpJsonLibrary.NewtonsoftJson:
+                        return "new Newtonsoft.Json.JsonConverter[] { " + string.Join(", ", jsonConverters.Select(c => "new " + c + "()")) + " }";
+
+                    case CSharpJsonLibrary.SystemTextJson:
+                        return "new System.Text.Json.Serialization.JsonConverter[] { " + string.Join(", ", jsonConverters.Select(c => "new " + c + "()")) + " }";
+
+                    default: // TODO: possibly add more json converters
+                        return string.Empty;
+                }
             }
             else
             {