Make sure Timber is the absolute last middleware inserted (#79)

* Make Timber is the absolute last middleware inserted

* Remove require

* Fix specs

* Cleanup

* Cleanup

* Rescue NameError

* Merge initializers now

lib/timber/frameworks/rails.rb

@@ -3,24 +3,64 @@ module Frameworks
     # Module for Rails specific code, such as the Railtie and any methods that assist
     # with Rails setup.
     module Rails
+      # Because of the crazy way Rails sorts it's initializers, it is
+      # impossible for Timber to be inserted after Devise's omnitauth
+      # middlewares.
+      # See: https://github.com/plataformatec/devise/blob/master/lib/devise/rails.rb#L22
+      # As such, we take a brute force approach here, ensuring we are inserted last
+      # no matter what. This ensures that we come after authentication so that we can
+      # properly set the user context.
+      #
+      # @private
+      module MiddlewareStackProxyFix
+        def self.included(klass)
+          klass.class_eval do
+            attr_accessor :timber_operations
+
+            alias old_merge_into merge_into
+
+            # This method does not exist for older versions of rails
+            begin
+              alias old_plus +
+            rescue NameError
+            end
+
+            def +(*args)
+              result = old_plus(*args)
+              result.timber_operations = timber_operations
+              result
+            end
+
+            def merge_into(*args)
+              if timber_operations
+                @operations -= timber_operations
+                @operations += timber_operations
+              end
+              old_merge_into(*args)
+            end
+          end
+        end
+      end
+
+      ::Rails::Configuration::MiddlewareStackProxy.send(:include, MiddlewareStackProxyFix)
+
       # Installs Timber into your Rails app automatically.
       class Railtie < ::Rails::Railtie
         config.timber = Config.instance
 
         # Initialize Timber immediately after the logger in case anything uses the logger
         # during the initialization process.
-        initializer(:timber, group: :all, after: :initialize_logger) do
+        initializer(:timber, after: :initialize_logger) do
           logger = Rails.ensure_timber_logger(::Rails.logger)
           Rails.set_logger(logger)
 
           Integrations.integrate!
-        end
 
-        # Ensures that we insert the middlewares last. We need to insert these last
-        # because initializers, such as Omniauth, insert middleware. If we are not
-        # after these initializers we will not capture user context, for example.
-        initializer(:timber_middlewares, after: :engines_blank_point) do
-          Rails.configure_middlewares(config.app_middleware)
+          timber_operations = Integrations::Rack.middlewares.collect do |middleware_class|
+            [:use, [middleware_class], nil]
+          end
+
+          config.app_middleware.timber_operations = timber_operations
         end
       end
 
@@ -60,17 +100,6 @@ def self.set_logger(logger)
         ::ActiveRecord::Base.logger = logger if defined?(::ActiveRecord::Base) && ::ActiveRecord::Base.respond_to?(:logger=)
         ::Rails.logger = logger
       end
-
-      def self.configure_middlewares(middleware)
-        var_name = :"@_timber_middlewares_inserted"
-        return true if middleware.instance_variable_defined?(var_name) && middleware.instance_variable_get(var_name) == true
-
-        # Rails uses a proxy :/, so we need to do this instance variable hack
-        middleware.instance_variable_set(var_name, true)
-        Integrations::Rack.middlewares.each do |middleware_class|
-          middleware.use middleware_class
-        end
-      end
     end
   end
 end