fromObject breaks oneof content

[alexander-fenster]

protobuf.js v6.10.2

In a kind of special case when oneof contains both a primitive field and a message, fromObject that is run on the instance of the static object would break the oneof by populating the primitive field with its default value.

Example:

test.proto

syntax = "proto3";

message TargetSpend {
  int32 micros = 1;
}

message OneofContainer {
  oneof campaign_bidding_strategy {
    string bidding_strategy = 1;
    TargetSpend target_spend = 2;
  }
}

repro.js

const protobuf = require('protobufjs');
const protos = require('./test.js');

const root = protobuf.Root.fromJSON(require('./test.json'));
const OneofContainer = root.lookup('OneofContainer');

const request = new protos.OneofContainer();
const targetSpend = new protos.TargetSpend();
targetSpend.micros = 1234;
request.targetSpend = targetSpend;

console.log(request);

const object = OneofContainer.fromObject(request);

console.log(object);

Commands to reproduce:

echo {} > package.json
npm install protobufjs
npx pbjs -t static-module -o test.js test.proto
npx pbjs -t json -o test.json test.proto
node repro.js

Result:

OneofContainer { targetSpend: TargetSpend { micros: 1234 } }    // before .fromObject
OneofContainer {
  biddingStrategy: '',
  targetSpend: TargetSpend { micros: 1234 }
}   // after .fromObject - the oneof is broken

Note that it work properly when fromObject is applied to a plain object:

const request1 = {
  targetSpend: {
    micros: 1234,
  }
};
const object1 = OneofContainer.fromObject(request1);
console.log(object1); // works

(I'm going to look into this, filing an issue just in case)

[alexander-fenster]

Upd. - after some thinking, it does not really matter if a oneof has a mix of primitive and non-primitive types; .fromObject will still do the wrong thing by assigning all oneof members a value.

[alexander-fenster]

Upd. - this only happens when a .fromObject method of a dynamically generated class is applied to an instance of a statically generated class (produced by pbjs).