fix: empty buffers submitted to a repeated bytes field were converted to undefined

[jawid-h]

I believe it is related to the following issue (#885). We're experiencing the same problem.

When we're having following message in .proto file:

message SomeMessage {
  repeated bytes objects = 1;
}

and trying to submit an empty Buffer in objects list field, the code compiled by protobufjs ignores it. I believe by having following statement:

else if (objects[i].length) ...

This PR fixes that by including zero-length buffers in the check.

[alexander-fenster]

@jawid-h The change looks good to us, could you add a test that would cover this situation? Thank you!

[vicb]

Hey @alexander-fenster

I would like to move this issue forward as it is causing some problems with the google datastore node client (googleapis/nodejs-datastore#755).

This is the test case I have tried to add to this PR:

            test.test(test.name + " - Message.toObject with empty buffers", function(test) {
                var msg = Message.create({
                    bytesVal: protobuf.util.newBuffer(0),
                });

                test.equal(Message.toObject(msg, { bytes: String }).bytesVal, "", "bytes to base64 strings");

                if (protobuf.util.isNode) {
                    const bytesVal = Message.toObject(msg, { bytes: Buffer }).bytesVal; 
                    test.ok(Buffer.isBuffer(bytesVal), "bytes to buffers");
                    test.equal(bytesVal.length, 0, "empty buffer");
                }

                test.end();
            });            

However it seems to be causing unrelated troubles.

Would you have any hints on the best way to test this PR ?

Thanks

[alexander-fenster]

Taken care of by #1514.