Redirect confirmed users to sign in

app/controllers/auth/confirmations_controller.rb

@@ -13,6 +13,8 @@ class Auth::ConfirmationsController < Devise::ConfirmationsController
       end
     elsif resource.errors.map(&:type).include?(:confirmation_period_expired)
       render "devise/confirmations/expired"
+    elsif resource.errors.map(&:type).include?(:already_confirmed)
+      redirect_to user_session_path
     else
       respond_with_navigational(resource.errors, status: :unprocessable_entity) { render :new }
     end

spec/requests/auth/confirmations_controller_spec.rb

@@ -43,4 +43,23 @@ RSpec.describe Auth::ConfirmationsController, type: :request do
       expect(page).to have_content("Your invitation link has expired")
     end
   end
+
+  context "when the user has already been confirmed" do
+    let(:user) { FactoryBot.create(:user, :data_provider, sign_in_count: 0, confirmed_at: Time.zone.now) }
+
+    before do
+      user.send_confirmation_instructions
+      get "/account/confirmation?confirmation_token=#{user.confirmation_token}"
+    end
+
+    it "redirects to the login page" do
+      follow_redirect!
+      expect(page).to have_content("Sign in to your account to submit CORE data")
+    end
+
+    it "does not show an error message" do
+      follow_redirect!
+      expect(page).not_to have_selector("#error-summary-title")
+    end
+  end
 end