Generalize ByteString conversion

Author: Havret

src/Protobuf.System.Text.Json/InternalConverters/ByteStringConverter.cs

@@ -1,5 +1,4 @@
 using System.Text.Json;
-using Google.Protobuf;
 
 namespace Protobuf.System.Text.Json.InternalConverters;
 
@@ -24,11 +23,6 @@ public static InternalConverter Create(FieldInfo fieldInfo, JsonSerializerOption
             var internalConverter = (InternalConverter) Activator.CreateInstance(typeof(ProtoEnumConverter), args: new object[] { fieldInfo.EnumType, jsonSerializerOptions.Encoder! })!;
             return internalConverter;
         }
-        else if (fieldInfo.FieldType == typeof(ByteString))
-        {
-            var internalConverter = new ByteStringConverter();
-            return internalConverter;
-        }
         else
         {
             var converterType = typeof(FieldConverter<>).MakeGenericType(fieldInfo.FieldType);

src/Protobuf.System.Text.Json/InternalConverters/InternalConverterFactory.cs

@@ -23,6 +23,7 @@ public static void AddProtobufSupport(this JsonSerializerOptions options, Action
         {
             options.Converters.Add(new TimestampConverter());
         }
+        options.Converters.Add(new ByteStringConverter());
         options.Converters.Add(new ProtobufJsonConverterFactory(jsonProtobufSerializerOptions));
     }
 

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

@@ -0,0 +1,26 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Google.Protobuf;
+
+namespace Protobuf.System.Text.Json.WellKnownTypesConverters;
+
+internal class ByteStringConverter : JsonConverter<ByteString?>
+{
+    public override ByteString? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        if (reader.GetString() is { } base64String)
+        {
+            return ByteString.FromBase64(base64String);
+        }
+
+        return null;
+    }
+
+    public override void Write(Utf8JsonWriter writer, ByteString? value, JsonSerializerOptions options)
+    {
+        if (value != null)
+        {
+            writer.WriteStringValue(value.ToBase64());
+        }
+    }
+}

src/Protobuf.System.Text.Json/WellKnownTypesConverters/ByteStringConverter.cs

@@ -8,5 +8,8 @@
         "a": 1
       }
     }
+  },
+  "mapStringToBytesType": {
+    "string_key": "YWJj"
   }
 }

test/Protobuf.System.Text.Json.Tests/MessageWithMapsTests.Should_serialize_message_with_map_field.approved.json

@@ -1,5 +1,6 @@
 using System.Text.Json;
 using System.Text.Json.Protobuf.Tests;
+using Google.Protobuf;
 using Protobuf.System.Text.Json.Tests.Utils;
 using Shouldly;
 using SmartAnalyzers.ApprovalTestsExtensions;
@@ -22,7 +23,8 @@ public void Should_serialize_message_with_map_field()
                 {
                     MapStringToInt = {["a"] = 1}
                 }
-            }
+            },
+            MapStringToBytesType = { ["string_key"] = ByteString.CopyFromUtf8("abc") }
         };
         var jsonSerializerOptions = TestHelper.CreateJsonSerializerOptions();
 
@@ -47,7 +49,8 @@ public void Should_deserialize_message_with_map_field()
                 {
                     MapStringToInt = {["a"] = 1}
                 }
-            }
+            },
+            MapStringToBytesType = { ["string_key"] = ByteString.CopyFromUtf8("abc") }
         };
         var jsonSerializerOptions = TestHelper.CreateJsonSerializerOptions();
 

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

@@ -5,6 +5,7 @@ option csharp_namespace = "System.Text.Json.Protobuf.Tests";
 message MessageWithMaps {
   map<int32, string> map_int_to_string = 1;
   map<string, NestedMessageAsKey> map_string_to_complex_type = 2;
+  map<string, bytes> map_string_to_bytes_type = 3;
 }
 
 message NestedMessageAsKey {