Rails 5 API only with Devise, OmniAuth, Devise Token Auth callback issue while Facebook sign in

Question

I am trying to create a Rails 5 API only app to create signin functionality with Facebook.

I am using the following gems:
devise_token_auth
omniauth_facebook

I have followed documentation on devise_token_auth to create the app. The demo app provided by them also have similar error.

I am able to sign in successfully. User's receiving token, it is increasing sign_in_count but after that callback is going to http://localhost:8000/auth/facebook/callback#_=_ with a blank page.

Below is the console log of the requests:

Started GET "/omniauth/facebook?resource_class=User" for 127.0.0.1 at <timestamp>
I, [2017-10-05T18:10:34.005009 #21485]  INFO -- omniauth: (facebook) Request phase initiated.
Started GET "/omniauth/facebook/callback?code=<code>" for 127.0.0.1 at <timestamp>
I, [2017-10-05T18:10:34.402585 #21485]  INFO -- omniauth: (facebook) Callback phase initiated.
Processing by DeviseTokenAuth::OmniauthCallbacksController#redirect_callbacks as HTML
  Parameters: {"code"=>"<code>", "state"=>"<state>", "provider"=>"facebook"}
Redirected to http://localhost:8000/auth/facebook/callback
Completed 302 Found in 1ms (ActiveRecord: 0.0ms)


Started GET "/auth/facebook/callback" for 127.0.0.1 at <timestamp>
Processing by DeviseTokenAuth::OmniauthCallbacksController#omniauth_success as HTML
  Parameters: {"provider"=>"facebook"}
  User Load (0.4ms)  SELECT  <SQL QUERY>
   (0.2ms)  begin transaction
  SQL (3.8ms)  UPDATE <SQL QUERY>
   (388.3ms)  commit transaction
   (0.1ms)  begin transaction
   (0.1ms)  commit transaction
Completed 200 OK in 566ms (Views: 0.2ms | ActiveRecord: 394.6ms)

I have also added omniauth_callbacks_controller.rb but it has no effect.

Code: https://github.com/tannakartikey/rails_api/

Answer 1

Just like with vanilla Devise you need to pass an option in the routes to specify a non-standard controller or it will generate routes to the default controllers provided by the gem:

Rails.application.routes.draw do
  mount_devise_token_auth_for 'User', at: 'auth', controllers: {
    omniauth_callbacks: 'users/omniauth_callbacks'
  } 

  mount_devise_token_auth_for 'Admin', at: 'admin_auth', controllers: {
    omniauth_callbacks: 'admins/omniauth_callbacks'
  } 

  as :admin do
    # Define routes for Admin within this block.
  end

  #scope module: 'api' do
    #namespace :v1 do
      #resources :users, only: [:show, :index]
    #end
  #end
end