Revert "Fix railsadminteam#3541 breaking on reload with parent_controller set"

This reverts commit 33e9214.

Author: wilg

lib/rails_admin.rb

@@ -32,7 +32,7 @@ def self.config(entity = nil, &block)
     if entity
       RailsAdmin::Config.model(entity, &block)
     elsif block_given?
-      RailsAdmin::Config::ConstLoadSuppressor.suppressing { yield(RailsAdmin::Config) }
+      suppress_const_load { yield(RailsAdmin::Config) }
     else
       RailsAdmin::Config
     end

lib/rails_admin/config.rb

@@ -270,12 +270,10 @@ def parent_controller=(name)
         @parent_controller = name
 
         if defined?(RailsAdmin::ApplicationController) || defined?(RailsAdmin::MainController)
-          RailsAdmin::Config::ConstLoadSuppressor.allowing do
-            RailsAdmin.send(:remove_const, :ApplicationController)
-            RailsAdmin.send(:remove_const, :MainController)
-            load RailsAdmin::Engine.root.join('app/controllers/rails_admin/application_controller.rb')
-            load RailsAdmin::Engine.root.join('app/controllers/rails_admin/main_controller.rb')
-          end
+          RailsAdmin.send(:remove_const, :ApplicationController)
+          RailsAdmin.send(:remove_const, :MainController)
+          load RailsAdmin::Engine.root.join('app/controllers/rails_admin/application_controller.rb')
+          load RailsAdmin::Engine.root.join('app/controllers/rails_admin/main_controller.rb')
         end
       end
 

lib/rails_admin/config/const_load_suppressor.rb

@@ -3,42 +3,14 @@
 module RailsAdmin
   module Config
     module ConstLoadSuppressor
-      class << self
-        @original_const_missing = nil
-
-        def suppressing
-          raise 'Constant Loading is already suppressed' if @original_const_missing
-
-          begin
-            @original_const_missing = Object.method(:const_missing)
-            intercept_const_missing
-            yield
-          ensure
-            Object.define_singleton_method(:const_missing, @original_const_missing)
-            @original_const_missing = nil
-          end
-        end
-
-        def allowing
-          if @original_const_missing
-            begin
-              Object.define_singleton_method(:const_missing, @original_const_missing)
-              yield
-            ensure
-              intercept_const_missing
-            end
-          else
-            yield
-          end
-        end
-
-      private
-
-        def intercept_const_missing
-          Object.define_singleton_method(:const_missing) do |name|
-            ConstProxy.new(name.to_s)
-          end
+      def suppress_const_load
+        original = Object.method(:const_missing)
+        Object.define_singleton_method(:const_missing) do |name|
+          ConstProxy.new(name.to_s)
         end
+        yield
+      ensure
+        Object.define_singleton_method(:const_missing, original)
       end
 
       class ConstProxy < BasicObject