Devise not displaying error messge during an authentication failure?

Question

I was expecting a flash notice when authentication failures occurs in devise. But get nothing during a authentication failure, just the page refreshes and remains still. I

Answer 1

I know this is old but I ended up here because I was having the same problem in rails 5.1 and the accepted answer didn't worked, so here's what I did. After overriding Devise::SessionController, add the following code to it:

after_action :unauthenticated

protected

def unauthenticated
  flash[:alert] = t("devise.failure.#{request.env['warden'].message}") unless request.env['warden'].message.blank?
end

Also, on the same controller, copy and paste the code for the create method from your version of Devise, and remove the ! from warden.authenticate!. Because you removed the !, now you have to check if the resource is nil, and redirect if it is. In my case, the create method ended up like this:

def create
  self.resource = warden.authenticate(auth_options)
  redirect_to root_path and return if resource.nil?
  set_flash_message!(:notice, :signed_in)
  sign_in(resource_name, resource)
  yield resource if block_given?
  respond_with resource, location: after_sign_in_path_for(resource)
end

Finally, you just have to print the flash messages on your views. I am using materialize, so I created a partial and added the following code to it (which you should customize to your own needs):

<% flash.each do |type, message| %>
  <% if type == "notice" %>
    
  <% elsif type == "success" %>
    
  <% elsif type == "alert" %>
    
  <% end %>
<% end %>