From 5bd980564a565906a6fda87d2ef31590d3e3b0a5 Mon Sep 17 00:00:00 2001
From: "M.Shibuya" <mit.shibuya@gmail.com>
Date: Sun, 17 Oct 2021 19:16:36 +0900
Subject: [PATCH] Fix config.parent_controller to work after the class loading

Fixes #2790, Refs. e4ae669
---
 .rubocop.yml                    |  2 +-
 lib/rails_admin/config.rb       | 10 +++++++++-
 spec/rails_admin/config_spec.rb | 19 +++++++++++++++++++
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/.rubocop.yml b/.rubocop.yml
index 47be7d15f8..eee69e98c7 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -108,7 +108,7 @@ Metrics/MethodLength:
   Max: 29 # TODO: Lower to 15
 
 Metrics/ModuleLength:
-  Max: 200 # TODO: Lower to 100
+  Max: 202 # TODO: Lower to 100
 
 Metrics/ParameterLists:
   Max: 8 # TODO: Lower to 4
diff --git a/lib/rails_admin/config.rb b/lib/rails_admin/config.rb
index 53efe0e222..46acf21c69 100644
--- a/lib/rails_admin/config.rb
+++ b/lib/rails_admin/config.rb
@@ -67,7 +67,7 @@ class << self
       attr_accessor :sidescroll
 
       # set parent controller
-      attr_accessor :parent_controller
+      attr_reader :parent_controller
 
       # set settings for `protect_from_forgery` method
       # By default, it raises exception upon invalid CSRF tokens
@@ -270,6 +270,14 @@ def default_hidden_fields=(fields)
         end
       end
 
+      def parent_controller=(name)
+        @parent_controller = name
+        if defined?(RailsAdmin::ApplicationController)
+          RailsAdmin.send(:remove_const, :ApplicationController)
+          load RailsAdmin::Engine.root.join('app/controllers/rails_admin/application_controller.rb')
+        end
+      end
+
       # Returns action configuration object
       def actions(&block)
         RailsAdmin::Config::Actions.instance_eval(&block) if block
diff --git a/spec/rails_admin/config_spec.rb b/spec/rails_admin/config_spec.rb
index 4294f62e07..637f38932a 100644
--- a/spec/rails_admin/config_spec.rb
+++ b/spec/rails_admin/config_spec.rb
@@ -262,6 +262,10 @@ class RecursivelyEmbedsMany
   end
 
   describe '.parent_controller' do
+    before do
+      class TestController < ActionController::Base; end
+    end
+
     it 'uses default class' do
       expect(RailsAdmin.config.parent_controller).to eq '::ActionController::Base'
     end
@@ -274,6 +278,21 @@ class RecursivelyEmbedsMany
     end
   end
 
+  describe '.parent_controller=' do
+    context 'if RailsAdmin::ApplicationController is already loaded' do
+      after do
+        RailsAdmin::Config.reset
+        RailsAdmin.send(:remove_const, :ApplicationController)
+        load RailsAdmin::Engine.root.join('app/controllers/rails_admin/application_controller.rb')
+      end
+
+      it 'can be changed' do
+        RailsAdmin.config.parent_controller = 'ApplicationController'
+        expect(RailsAdmin::ApplicationController.superclass).to eq ApplicationController
+      end
+    end
+  end
+
   describe '.forgery_protection_settings' do
     it 'uses with: :exception by default' do
       expect(RailsAdmin.config.forgery_protection_settings).to eq(with: :exception)