Adds current_active_session helper.

Closes #93, "Why is the ||= removed? current_user method".  This adds
memoization back to current_user / Current.user, plus causes log out
when the current session is destroyed.

app/controllers/active_sessions_controller.rb

@@ -2,16 +2,16 @@ class ActiveSessionsController < ApplicationController
   before_action :authenticate_user!
 
   def destroy
-    @active_session = current_user.active_sessions.find(params[:id])
+    active_session = current_user.active_sessions.find(params[:id])
 
-    @active_session.destroy
-
-    if current_user
-      redirect_to account_path, notice: "Session deleted."
-    else
+    if active_session == current_active_session
       forget_active_session
+      active_session.destroy
       reset_session
       redirect_to root_path, notice: "Signed out."
+    else
+      active_session.destroy
+      redirect_to account_path, notice: "Session deleted."
     end
   end
 

app/controllers/concerns/authentication.rb

@@ -3,6 +3,7 @@ module Authentication
 
   included do
     before_action :current_user
+    helper_method :current_active_session
     helper_method :current_user
     helper_method :user_signed_in?
   end
@@ -41,10 +42,14 @@ def remember(active_session)
   private
 
   def current_user
-    Current.user = if session[:current_active_session_id].present?
-      ActiveSession.find_by(id: session[:current_active_session_id])&.user
+    Current.user ||= current_active_session&.user
+  end
+
+  def current_active_session
+    Current.active_session ||= if session[:current_active_session_id].present?
+      ActiveSession.find_by(id: session[:current_active_session_id])
     elsif cookies[:remember_token]
-      ActiveSession.find_by(remember_token: cookies.encrypted[:remember_token])&.user
+      ActiveSession.find_by(remember_token: cookies.encrypted[:remember_token])
     end
   end
 

app/models/current.rb

@@ -1,3 +1,4 @@
 class Current < ActiveSupport::CurrentAttributes
   attribute :user
+  attribute :active_session
 end