Missing special handling for json 'null' value for google.protobuf.NullValue

[GVladi]

According to the documentation https://github.com/protocolbuffers/protobuf/blob/main/src/google/protobuf/struct.proto
for google.protobuf.NullValue type:

// `NullValue` is a singleton enumeration to represent the null value for the
// `Value` type union.
//
// The JSON representation for `NullValue` is JSON `null`.
enum NullValue {
  // Null value.
  NULL_VALUE = 0;
}

json null value has to be interpreted as NULL_VALUE.

It seems to be not the case.

My TestMessage has a field as follows:

  google.protobuf.NullValue null_value = 1;

When I try to send the following payload:

  "null_value": null

I am getting an error:

"Error invoking method "TestService/test": error getting request data: message type TestMessage cannot set field null_value to null: it is not a message type".

If I handle the NullValue as an enum and send the following payload:

  "null_value": "NULL_VALUE"

the request succeeds.

I would expect json null to be handled in the same as the "NULL_VALUE".