fix(auth): Use 'owner' token when communicating with Auth emulator

[samtstern]

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Discussion

Fixes #1077

Testing

Wrote a simple test.js script:

const admin = require('firebase-admin');
admin.initializeApp({
  projectId: 'fir-dumpster'
});

async function main() {
  console.log(`FIREBASE_AUTH_EMULATOR_HOST=${process.env.FIREBASE_AUTH_EMULATOR_HOST}`);
  const user = await admin.auth().createUser({
    uid: "user" + new Date().getTime()
  });

  console.log("Created: ", user.uid)
}

main();

When executed as normal:

$ node test.js 
FIREBASE_AUTH_EMULATOR_HOST=undefined
(node:37745) UnhandledPromiseRejectionWarning: Error: Credential implementation provided to initializeApp() via the "credential" property failed to fetch a valid Google OAuth2 access token with the following error: "Error fetching access token: Error while making request: getaddrinfo ENOTFOUND metadata.google.internal metadata.google.internal:80. Error code: ENOTFOUND".
    at FirebaseAppError.FirebaseError [as constructor] (/Users/samstern/Projects/firebase-admin-node/lib/utils/error.js:43:28)
    at FirebaseAppError.PrefixedFirebaseError [as constructor] (/Users/samstern/Projects/firebase-admin-node/lib/utils/error.js:89:28)
    at new FirebaseAppError (/Users/samstern/Projects/firebase-admin-node/lib/utils/error.js:124:28)
    at /Users/samstern/Projects/firebase-admin-node/lib/firebase-app.js:122:23
    at process._tickCallback (internal/process/next_tick.js:68:7)
(node:37745) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:37745) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

When executed in the emulators:

$ firebase emulators:exec "node test.js"
i  emulators: Starting emulators: auth, functions
⚠  functions: The following emulators are not running, calls to these services from the Functions emulator will affect production: firestore, database, hosting, pubsub
⚠  Your requested "node" version "12" doesn't match your global version "10"
i  functions: Watching "/private/var/folders/xl/6lkrzp7j07581mw8_4dlt3b000643s/T/tmp.35bA7OYr/functions" for Cloud Functions...
i  Running script: node test.js
FIREBASE_AUTH_EMULATOR_HOST=localhost:9099
Created:  user1604932585692
✔  Script exited successfully (code 0)
i  emulators: Shutting down emulators.
i  functions: Stopping Functions Emulator
i  auth: Stopping Authentication Emulator
i  hub: Stopping emulator hub

API Changes

N/A

[hiranya911]

I'd suggest a simpler implementation like the following:

1. Change the AuthorizedHttpClient so child classes can override how it fetches tokens:

export class AuthorizedHttpClient extends HttpClient {
  constructor(private readonly app: FirebaseApp) {
    super();
  }

  protected getToken(): Promise<string> {
    return this.app.INTERNAL.getToken().then((result) => {
      return result.accessToken;
    });
  }

}

2. Then in the Auth module extend the above class, and override getToken():

class AuthHttpClient extends AuthorizedHttpClient {
  constructor(app: FirebaseApp, private readonly useEmulator: boolean) {
    super(app);
  }

  protected getToken(): Promise<string> {
    if (this.useEmulator) {
      return Promise.resolve('owner');
    }

    return super.getToken();
  }
}

export abstract class AbstractAuthRequestHandler {
  constructor(protected readonly app: FirebaseApp, useEmulator: boolean) {
    this.httpClient = new AuthHttpClient(app, useEmulator); 
  }
}

[samtstern]

@hiranya911 thanks for the comments! You're right that's much cleaner.

[hiranya911]

LGTM with a suggestion.

[hiranya911]

Actually, can I ask you to add some test cases for this change?

Hiranya and Bassam asked for the same things

[hiranya911]

Thank! LGTM with a couple of nits.

[nVitius]

I know this was merged very recently, but when can we expect to see this in a tagged release?

[samtstern]

@nVitius we don't have a strict release cadence but if you look at the past we've released about once a month or so:
https://github.com/firebase/firebase-admin-node/releases

This change will be included in the next release. If you want to use it right now you can always clone the master branch of this GitHub repo and npm install the dependency locally!

[samtstern]

@nVitius well you got lucky ... the 9.4.0 release with this fix went out!