[App] Certain app names cause issues

[jsayol]

[REQUIRED] Describe your environment

• Operating System version: Linux
• Firebase SDK version: 4.1.2
• Firebase Product: app

[REQUIRED] Describe the problem

Using the name of any Object.prototype member as an app name causes issues when trying to initialize or retrieve an app.

Steps to reproduce:

// Here we get an error saying there already is a "valueOf" app
try {
  firebase.initializeApp(options, 'valueOf');
} catch (err) {
  console.error(err.code + ' - ' + err.message);
}

// This simply returns the Object.prototype.toString method
const app = firebase.app('toString');
console.log(app);

Relevant Code:

JSBin reproducing these issues: http://jsbin.com/cohijesema/edit?js,console

[google-oss-bot]

Hey there! I couldn't figure out what this issue is about, so I've labeled it for a human to triage. Hang tight.

[jsayol]

I see 2 possible approaches to address this:

1. Allow any app name, like it's supposed to work now, and modify any relevant code to support this.
2. Disallow using the name of any Object.prototype member as an app name by introducing any relevant checks. firebase.initializeApp() would throw an app/bad-app-name error and firebase.app() would throw an app/no-app error.

Personally, I strongly prefer the first option. There's no reason why toString shouldn't be an allowed app name.

Thoughts?