Cast "oneOf" value to a single value when converting to dict/JSON

[jvaesteves]

I am currently consuming metrics exposed by an OpenTelemetry agent, but when I try to convert the Protobuf metrics to JSON, the "oneOf" occurences are being translated to a dict instead of a single value. Is there any way to change this behavior to only display a single string value?

An example of what is happening:

The proto definitions (the original .proto files can be found here):

syntax = "proto3";

message AnyValue {
  oneof value {
    string string_value = 1;
    bool bool_value = 2;
    int64 int_value = 3;
    double double_value = 4;
    ArrayValue array_value = 5;
    KeyValueList kvlist_value = 6;
    bytes bytes_value = 7;
  }
}

message ArrayValue {
  repeated AnyValue values = 1;
}

message KeyValueList {
  repeated KeyValue values = 1;
}

message KeyValue {
  string key = 1;
  AnyValue value = 2;
}

The dataclasses generated:

@dataclass
class KeyValue(betterproto.Message):
    key: str = betterproto.string_field(1)
    value: "AnyValue" = betterproto.message_field(2)

@dataclass
class AnyValue(betterproto.Message):
    string_value: str = betterproto.string_field(1, group="value")
    bool_value: bool = betterproto.bool_field(2, group="value")
    int_value: int = betterproto.int64_field(3, group="value")
    double_value: float = betterproto.double_field(4, group="value")
    array_value: "ArrayValue" = betterproto.message_field(5, group="value")
    kvlist_value: "KeyValueList" = betterproto.message_field(6, group="value")
    bytes_value: bytes = betterproto.bytes_field(7, group="value")

The current conversion:

{"key": "process.pid", "value": {"intValue": "275"}}

What I would like to have:

{"key": "process.pid", "value": "275"}