How to get the auth URL from an OmniAuth provider without redirect

Question

How do you get the URL that OmniAuth redirect to when you go to /auth/twitter?

I am building an API server and just want to pass the URL in JSON to the client so it can do whatever it needs to with the URL.

I think what I want is the result of the strategy's request_phase as that looks to be the auth URL, but how do I get that in a new controller so I can do:

class MyOauthController < ApplicationController
  # GET /my_oauth/signin/twitter.json
  def signin
    url = ???
    render json: {signin_url: url}
  end

Is there a clean way to do this?

Answer 1

Yes, Omniauth provides a helper function for you:

user_omniauth_authorize_path(key)
# for your case
user_omniauth_authorize_path("twitter")

Check out their Devise overview.

Answer 2

Is there a clean way to do this?

Not directly, no - vanilla OmniAuth doesn't generate routes by itself. It uses something called "Rack middleware" which would intercept request outside of Ruby on Rails context and hence wouldn't need a Rails route to function.

The Evan's answer above is dependent on Devise gem, which is not strict requirement for OmniAuth (you may have it bundled & loaded or may not have it).

A cleaner alternative to blatant copy & pasting the relative route around may be some wrapper method/helper that could contain "/auth/twitter" reference to a single place/be more DRY.