apiでdevise認証を叩いてUnauthorizedな時に, redirectなhtmlじゃなくて401のjsonを返したい

ref: How To: Redirect to a specific page when the user can not be authenticated · plataformatec/devise Wiki

Devise::FailureAppを継承したCustomFailureを作成, respondメソッドを書き換えてcontent typeがapplication/jsonだったらjson返すようにした. コレ自体がRack appなのか, self.status = 401, という書き換え方で面白い. bodyはとりあえずという感じ.

lib/custom_failure.rb

class CustomFailure < Devise::FailureApp
  def respond
    if http_auth?
      http_auth
    # ここのelsif句を追加
    elsif request.content_type == "application/json"
      self.status = 401
      self.content_type = "application/json"
      self.response_body = {success: false, error: "Unauthorized"}.to_json
    else
      redirect
    end
  end
end

あとlibの読み込み順を先にして,

config/application.rb

config.autoload_paths += %W(#{config.root}/lib)

deviseの設定に加えればok

config/initializers/devise.rb

  config.warden do |manager|
    manager.failure_app = CustomFailure
  end