Finish oneof support

[melonmouse]

Thanks so much for working on this project! Hope this bug will help :). I looked at your code for a bit to see if I could write you a pull request, but wasn't sure where to start.

To complete oneof support, there should be helper functions to determine what case is set.
https://developers.google.com/protocol-buffers/docs/reference/javascript-generated#oneof

So taking the example from above:

package account;
message Profile {
  oneof avatar {
    string image_url = 1;
    bytes image_data = 2;
  }
}

There should be a generated enum representing the cases, so for the above example:

proto.account.Profile.AvatarCase = {
  AVATAR_NOT_SET: 0,
  IMAGE_URL: 1,
  IMAGE_DATA: 2
};

And a getter that returns the enum value that is currently set, getAvatarCase().

[melonmouse]

P.S. if it is any help, if you'd write a "pseudo code" commit adding this functionality, I could complete that. Not sure if it would save you time, but wanted to offer :)

[thesayyn]

Hey, thank you for opening this. We had a brief conversation on another issue.

It makes more sense to continue the conversation here.

P.S. if it is any help, if you'd write a "pseudo code" commit adding this functionality, I could complete that. Not sure if it would save you time, but wanted to offer :)

I can assist you on the way if you could open up a draft pull request.

[thesayyn]

Hey @melonmouse

When you have some time, could you join the discussion at #39 about one-of-fields?

@melonmouse I have sent PR for this feature on #53

[jackpunt]

Sahin, sorry to be late getting to this, I've been off for the summer.
It seems that this needs a bit more work; consider:

message TypedMsg {
  oneof value {
    bool boolValue = 3;
    int32 intValue = 4;
    string strValue = 5;
  }
}

I believe it should be the case that:

let msgInt = new TypedMsg({intValue: 23})
let msgStr = new TypedMsg(strValue: "foo"})
assert( msgInt.intValue === 23)      // works
assert( msgStr.strValue === "foo")   // works
assert( msgInt.value === 23)         // fails: msgInt.value === "intValue"
assert( msgStr.value === "foo")      // fails: msgStr.value === "strValue"

The type of TypedValue.value should be: number | string | boolean | void [or | undefined? i'm not an expert on that ]
rather than: "intValue" | "strValue" | "boolValue" | "none"