Add PropertyNameCaseInsensitive support

Author: Havret

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

@@ -12,7 +12,7 @@ namespace Protobuf.System.Text.Json;
     private readonly FieldInfo[] _fields;
     private readonly Dictionary<string, FieldInfo> _fieldsLookup;
 
-    public ProtobufConverter(JsonNamingPolicy? namingPolicy, JsonProtobufSerializerOptions options)
+    public ProtobufConverter(JsonSerializerOptions jsonSerializerOptions, JsonProtobufSerializerOptions jsonProtobufSerializerOptions)
     {
         var type = typeof(T);
 
@@ -21,7 +21,7 @@ public ProtobufConverter(JsonNamingPolicy? namingPolicy, JsonProtobufSerializerO
         var propertyInfo = type.GetProperty("Descriptor", BindingFlags.Public | BindingFlags.Static);
         var messageDescriptor = (MessageDescriptor) propertyInfo?.GetValue(null, null)!;
 
-        var convertNameFunc = GetConvertNameFunc(namingPolicy, options.UseProtobufJsonNames);
+        var convertNameFunc = GetConvertNameFunc(jsonSerializerOptions.PropertyNamingPolicy, jsonProtobufSerializerOptions.UseProtobufJsonNames);
 
         _fields = messageDescriptor.Fields.InDeclarationOrder().Select(fieldDescriptor => new FieldInfo
         {
@@ -33,7 +33,8 @@ public ProtobufConverter(JsonNamingPolicy? namingPolicy, JsonProtobufSerializerO
             IsOneOf = fieldDescriptor.ContainingOneof != null
         }).ToArray();
 
-        _fieldsLookup = _fields.ToDictionary(x => x.JsonName, x => x);
+        var stringComparer = jsonSerializerOptions.PropertyNameCaseInsensitive ? StringComparer.OrdinalIgnoreCase : StringComparer.Ordinal;
+        _fieldsLookup = _fields.ToDictionary(x => x.JsonName, x => x, stringComparer);
     }
 
     private static Func<FieldDescriptor, string> GetConvertNameFunc(JsonNamingPolicy? jsonNamingPolicy, bool useProtobufJsonNames)

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

@@ -18,9 +18,9 @@ public override bool CanConvert(Type typeToConvert)
         return typeof(IMessage).IsAssignableFrom(typeToConvert);
     }
 
-    public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializerOptions options)
+    public override JsonConverter CreateConverter(Type typeToConvert, JsonSerializerOptions jsonSerializerOptions)
     {
         var converterType = typeof(ProtobufConverter<>).MakeGenericType(typeToConvert);
-        return (JsonConverter) Activator.CreateInstance(converterType, new object[] {options.PropertyNamingPolicy, _options})!;
+        return (JsonConverter) Activator.CreateInstance(converterType, new object[] {jsonSerializerOptions, _options})!;
     }
 }

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

@@ -0,0 +1,35 @@
+using System.Text.Json;
+using System.Text.Json.Protobuf.Tests;
+using Shouldly;
+using Xunit;
+
+namespace Protobuf.System.Text.Json.Tests;
+
+public class PropertyNameCaseInsensitiveTests
+{
+    [Fact]
+    public void Should_support_PropertyNameCaseInsensitive_setting()
+    {
+        var originalMessage = new SimpleMessage
+        {
+            DoubleProperty = 2.5d
+        };
+        
+        // Serialize message using PascalCase naming policy (default)
+        var serializerOptions = new JsonSerializerOptions();
+        serializerOptions.AddProtobufSupport();
+        
+        var payload = JsonSerializer.Serialize(originalMessage, serializerOptions);
+        
+        // Deserialize message using CamelCase naming policy (custom)
+        // with PropertyNameCaseInsensitive option set to true
+        var deserializerOptions = new JsonSerializerOptions();
+        deserializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
+        deserializerOptions.PropertyNameCaseInsensitive = true;
+        deserializerOptions.AddProtobufSupport();
+        
+        var deserialized = JsonSerializer.Deserialize<SimpleMessage>(payload, deserializerOptions);
+        
+        deserialized.ShouldBeEquivalentTo(originalMessage);
+    }
+}