Redirect all controllers to login if required

We want to skip the filter for sessions controller so that we can login
and we want to skip the filter for static pages because those should be
visible to visitors.

app/controllers/application_controller.rb

@@ -22,6 +22,7 @@ class ApplicationController < ActionController::Base
   before_filter :preload_json
   before_filter :check_xhr
   before_filter :set_locale
+  before_filter :redirect_to_login_if_required
 
   rescue_from Exception do |exception|
     unless [ ActiveRecord::RecordNotFound, ActionController::RoutingError,
@@ -280,6 +281,10 @@ class ApplicationController < ActionController::Base
       raise Discourse::NotLoggedIn.new unless current_user.present?
     end
 
+    def redirect_to_login_if_required
+      redirect_to :login if SiteSetting.login_required? && !current_user
+    end
+
     def render_not_found_page(status=404)
       f = Topic.where(deleted_at: nil, archetype: "regular")
       @latest = f.order('views desc').take(10)

app/controllers/session_controller.rb

@@ -4,6 +4,7 @@ class SessionController < ApplicationController
   #  page is going to be empty, this means that server will see an invalid CSRF and blow the session
   #  once that happens you can't log in with social
   skip_before_filter :verify_authenticity_token, only: [:create]
+  skip_before_filter :redirect_to_login_if_required
 
   def create
     requires_parameter(:login, :password)

app/controllers/static_controller.rb

@@ -1,6 +1,6 @@
 class StaticController < ApplicationController
 
-  skip_before_filter :check_xhr
+  skip_before_filter :check_xhr, :redirect_to_login_if_required
 
   def show
 

spec/controllers/topics_controller_spec.rb

@@ -435,6 +435,25 @@ describe TopicsController do
 
     end
 
+    context "when 'login required' site setting has been enabled" do
+      before { SiteSetting.stubs(:login_required?).returns(true) }
+
+      context 'and the user is logged in' do
+        before { log_in(:coding_horror) }
+
+        it 'shows the topic' do
+          get :show, topic_id: topic.id, slug: topic.slug
+          expect(response).to be_successful
+        end
+      end
+
+      context 'and the user is not logged in' do
+        it 'redirects to the login page' do
+          get :show, topic_id: topic.id, slug: topic.slug
+          expect(response).to redirect_to login_path
+        end
+      end
+    end
   end
 
   describe '#feed' do