Wrong error fired on useServiceWorker() called second time

[zezic]

• Operating System version: Ubuntu 16.04 (don't matter)
• Firebase SDK version: 4.1.5
• Firebase Product: messaging

Steps to reproduce:

Call firebase.messaging().useServiceWorker(sw_registration) second time and get wrong error message: USE_SW_BEFORE_GET_TOKEN
There should be some warning about repeated assigning of Service Worker because we don't try to get token here, only assign Service Worker.

Relevant Code:

let firebase = require('firebase/app')
require('firebase/messaging')
firebase.initializeApp({
  messagingSenderId: FCM_SENDER_ID
})
firebase.messaging().useServiceWorker(sw_registration)
firebase.messaging().useServiceWorker(sw_registration) // wrong error here

[google-oss-bot]

Hmmm this issue does not seem to follow the issue template. Make sure you provide all the required information.

[gauntface]

@zezic thanks for raising the issue, will look into this when I can.

[rejhgadellaa]

FYI, looks like it's also present in 4.2.0

[gauntface]

The error message does need changing. I hadn't intended that developers would call this method twice, out of interest what is the use case?

The reason for enforcing a single call is to avoid any risk of the library being called with two different service workers.

So would people prefer the ability to just allow any number of calls and block after getToken is called or would they prefer only being able to call it once and just have the error corrected to something along the lines of "useServiceWorker can only be called once and must be called before getToken()" ?