Redirect to password reset in case of existing user

app/controllers/registrations_controller.rb

@@ -3,6 +3,17 @@
 class RegistrationsController < Devise::RegistrationsController
   prepend_before_action :check_captcha, only: [:create]
 
+  def create
+    existing_user = User.find_by(email: sign_up_params[:email])
+    if existing_user
+      flash[:notice] = 'An account with this email already exists. Please reset your password to sign in.'
+      redirect_to new_user_password_path(user: { email: sign_up_params[:email] })
+      return
+    end
+
+    super
+  end
+
   protected
 
   def after_update_path_for(resource)

app/views/devise/passwords/new.html.haml

@@ -10,7 +10,7 @@
             .form-group
               = f.label :email, "Email"
               %abbr{title: 'This field is required'} *
-              = f.email_field :email, autofocus: true, required: true, class: 'form-control', placeholder: 'Email'
+              = f.email_field :email, autofocus: true, required: true, class: 'form-control', placeholder: 'Email', value: params.dig(:user, :email)
             %p.text-right
               %button{type: 'submit', class: 'btn btn-success'}
                 Send me reset password instructions