Use property naming policy

Author: Havret

src/System.Text.Json.Protobuf/JsonProtobufSerializerOptions.cs

@@ -0,0 +1,12 @@
+namespace System.Text.Json.Protobuf;
+
+public class JsonProtobufSerializerOptions
+{
+    /// <summary>
+    /// Defines how property names should be resolved for protobuf contracts.
+    /// When set to true PropertyNamingPolicy will be ignored and property name will be derived from protobuf contract.
+    /// This is usually the lower-camel-cased form of the field name, but can be overridden using the <c>json_name</c>
+    /// option in the .proto file.
+    /// </summary>
+    public bool UseProtobufJsonNames { get; set; }
+}

src/System.Text.Json.Protobuf/JsonSerializerOptionsExtensions.cs

@@ -5,9 +5,25 @@ namespace System.Text.Json;
 
 public static class JsonSerializerOptionsExtensions
 {
-    public static void AddProtobufSupport(this JsonSerializerOptions options)
+    /// <summary>
+    /// Adds support for Protobuf contracts to JsonSerializer.
+    /// </summary>
+    /// <param name="options">The <see cref="T:System.Text.Json.JsonSerializerOptions" />.</param>
+    /// <param name="configure">An <see cref="T:System.Action" /> to configure the <see cref="T:System.Text.Json.Protobuf.JsonProtobufSerializerOptions" />.</param>
+    public static void AddProtobufSupport(this JsonSerializerOptions options, Action<JsonProtobufSerializerOptions> configure)
     {
+        var jsonProtobufSerializerOptions = new JsonProtobufSerializerOptions();
+        configure.Invoke(jsonProtobufSerializerOptions);
         options.Converters.Add(new TimestampConverter());
-        options.Converters.Add(new ProtobufJsonConverterFactory());
+        options.Converters.Add(new ProtobufJsonConverterFactory(jsonProtobufSerializerOptions));
+    }
+    
+    /// <summary>
+    /// Adds support for Protobuf contracts to JsonSerializer.
+    /// </summary>
+    /// <param name="options">The <see cref="T:System.Text.Json.JsonSerializerOptions" />.</param>
+    public static void AddProtobufSupport(this JsonSerializerOptions options)
+    {
+        options.AddProtobufSupport(_ => {});
     }
 }

src/System.Text.Json.Protobuf/ProtobufConverter.cs

@@ -11,23 +11,40 @@ namespace System.Text.Json.Protobuf;
     private readonly FieldInfo[] _fields;
     private readonly Dictionary<string, FieldInfo> _fieldsLookup;
 
-    public ProtobufConverter()
+    public ProtobufConverter(JsonNamingPolicy? namingPolicy, JsonProtobufSerializerOptions options)
     {
         var propertyInfo = typeof(T).GetProperty("Descriptor", BindingFlags.Public | BindingFlags.Static);
         var messageDescriptor = (MessageDescriptor) propertyInfo?.GetValue(null, null)!;
 
+        var convertNameFunc = GetConvertNameFunc(namingPolicy, options.UseProtobufJsonNames);
+
         _fields = messageDescriptor.Fields.InDeclarationOrder().Select(fieldDescriptor => new FieldInfo
         {
             Accessor = fieldDescriptor.Accessor,
             IsRepeated = fieldDescriptor.IsRepeated,
             FieldType = GetFieldType(fieldDescriptor),
-            JsonName = fieldDescriptor.JsonName,
+            JsonName = convertNameFunc(fieldDescriptor),
             IsOneOf = fieldDescriptor.ContainingOneof != null
         }).ToArray();
 
         _fieldsLookup = _fields.ToDictionary(x => x.JsonName, x => x);
     }
 
+    private static Func<FieldDescriptor, string> GetConvertNameFunc(JsonNamingPolicy? jsonNamingPolicy, bool useProtobufJsonNames)
+    {
+        if (useProtobufJsonNames)
+        {
+            return descriptor => descriptor.JsonName;
+        }
+
+        if (jsonNamingPolicy != null)
+        {
+            return descriptor => jsonNamingPolicy.ConvertName(descriptor.PropertyName);
+        }
+
+        return descriptor => descriptor.PropertyName;
+    }
+
     public override T Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
     {
         var obj = new T();

src/System.Text.Json.Protobuf/ProtobufJsonConverterFactory.cs

@@ -5,6 +5,13 @@ namespace System.Text.Json.Protobuf;
 
 internal class ProtobufJsonConverterFactory : JsonConverterFactory
 {
+    private readonly JsonProtobufSerializerOptions _options;
+
+    public ProtobufJsonConverterFactory(JsonProtobufSerializerOptions options)
+    {
+        _options = options;
+    }
+
     public override bool CanConvert(Type typeToConvert)
     {
         return typeToConvert.IsAssignableTo(typeof(IMessage));
@@ -13,6 +20,6 @@ public override bool CanConvert(Type typeToConvert)
     public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializerOptions options)
     {
         var converterType = typeof(ProtobufConverter<>).MakeGenericType(typeToConvert);
-        return (JsonConverter) Activator.CreateInstance(converterType)!;
+        return (JsonConverter) Activator.CreateInstance(converterType, new object[]{options.PropertyNamingPolicy, _options})!;
     }
 }

test/System.Text.Json.Protobuf.Tests/JsonNamingPolicyTests.Should_ignore_PropertyNamingPolicy_when_UseProtobufJsonNames_set_to_true.approved.json

@@ -0,0 +1,16 @@
+{
+  "doubleProperty": 2.5,
+  "floatProperty": 0,
+  "int32Property": 0,
+  "int64Property": 0,
+  "uint32Property": 0,
+  "uint64Property": 0,
+  "sint32Property": 0,
+  "sint64Property": 0,
+  "fixed32Property": 0,
+  "fixed64Property": 0,
+  "sfixed32Property": 0,
+  "sfixed64Property": 0,
+  "boolProperty": false,
+  "stringProperty": ""
+}

test/System.Text.Json.Protobuf.Tests/JsonNamingPolicyTests.Should_serialize_message_with_primitive_types.approved.json

@@ -0,0 +1,16 @@
+{
+  "doubleproperty": 2.5,
+  "floatproperty": 0,
+  "int32property": 0,
+  "int64property": 0,
+  "uint32property": 0,
+  "uint64property": 0,
+  "sint32property": 0,
+  "sint64property": 0,
+  "fixed32property": 0,
+  "fixed64property": 0,
+  "sfixed32property": 0,
+  "sfixed64property": 0,
+  "boolproperty": false,
+  "stringproperty": ""
+}

test/System.Text.Json.Protobuf.Tests/JsonNamingPolicyTests.cs

@@ -0,0 +1,55 @@
+using System.Text.Json.Protobuf.Tests.Utils;
+using SmartAnalyzers.ApprovalTestsExtensions;
+using Xunit;
+
+namespace System.Text.Json.Protobuf.Tests;
+
+public class JsonNamingPolicyTests
+{
+    [Fact]
+    public void Should_serialize_message_with_primitive_types()
+    {
+        // Arrange
+        var msg = new SimpleMessage
+        {
+            DoubleProperty = 2.5d
+        };
+        var jsonSerializerOptions = TestHelper.CreateJsonSerializerOptions();
+        jsonSerializerOptions.PropertyNamingPolicy = new JsonLowerCaseNamingPolicy();
+
+        // Act
+        var serialized = JsonSerializer.Serialize(msg, jsonSerializerOptions);
+
+        // Assert
+        var approver = new ExplicitApprover();
+        approver.VerifyJson(serialized);
+    }
+    
+    [Fact]
+    public void Should_ignore_PropertyNamingPolicy_when_UseProtobufJsonNames_set_to_true()
+    {
+        // Arrange
+        var msg = new SimpleMessage
+        {
+            DoubleProperty = 2.5d
+        };
+        var jsonSerializerOptions = new JsonSerializerOptions();
+        jsonSerializerOptions.PropertyNamingPolicy = new JsonLowerCaseNamingPolicy();
+        jsonSerializerOptions.AddProtobufSupport(options => options.UseProtobufJsonNames = true);
+        
+        // Act
+        var serialized = JsonSerializer.Serialize(msg, jsonSerializerOptions);
+
+        // Assert
+        var approver = new ExplicitApprover();
+        approver.VerifyJson(serialized);
+    }
+
+    private class JsonLowerCaseNamingPolicy : JsonNamingPolicy
+    {
+        public override string ConvertName(string name)
+        {
+            return name.ToLower();
+        }
+    }
+}

test/System.Text.Json.Protobuf.Tests/Utils/TestHelper.cs

@@ -5,6 +5,7 @@ public class TestHelper
     public static JsonSerializerOptions CreateJsonSerializerOptions()
     {
         var jsonSerializerOptions = new JsonSerializerOptions();
+        jsonSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
         jsonSerializerOptions.AddProtobufSupport();
         return jsonSerializerOptions;
     }