Ensure application gets reloaded only once

Closes activeadmin#5739

.circleci/config.yml

@@ -89,6 +89,7 @@ version: 2.1
     command: |
       COVERAGE=true PARALLEL_TEST_PROCESSORS=4 bin/parallel_rspec spec/
       COVERAGE=true RSPEC_FILESYSTEM_CHANGES=true bin/rspec
+      COVERAGE=true CLASS_RELOADING=true bin/rspec
 
 .run_features: &run_features
   run:

.rspec

@@ -1,3 +1,4 @@
 --format <%= ENV['CI'] ? 'documentation' : 'progress' %>
 --require spec_helper
 <%= "--require #{__dir__}/spec/support/simplecov_changes_env.rb --tag changes_filesystem" if ENV['RSPEC_FILESYSTEM_CHANGES'] %>
+<%= "--require #{__dir__}/spec/support/simplecov_reload_env.rb --tag requires_reloading" if ENV['CLASS_RELOADING'] %>

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Bug Fixes
+
+* Ensure application gets reloaded only once. [#5740] by [@jscheid]
+
 ### Removals
 
 * Support for ruby 2.3 has been removed. [#5751] by [@deivid-rodriguez]
@@ -439,6 +443,7 @@ Please check [0-6-stable] for previous changes.
 [#5662]: https://github.com/activeadmin/activeadmin/pull/5662
 [#5726]: https://github.com/activeadmin/activeadmin/pull/5726
 [#5738]: https://github.com/activeadmin/activeadmin/pull/5738
+[#5740]: https://github.com/activeadmin/activeadmin/pull/5740
 [#5751]: https://github.com/activeadmin/activeadmin/pull/5751
 
 [@5t111111]: https://github.com/5t111111
@@ -504,3 +509,4 @@ Please check [0-6-stable] for previous changes.
 [@chrp]: https://github.com/chrp
 [@bartoszkopinski]: https://github.com/bartoszkopinski
 [@panasyuk]: https://github.com/panasyuk
+[@jscheid]: https://github.com/jscheid

lib/active_admin/application.rb

@@ -187,17 +187,8 @@ def remove_active_admin_load_paths_from_rails_autoload_and_eager_load
     # regenerate the routes as well.
     def attach_reloader
       Rails.application.config.after_initialize do |app|
-        unload_active_admin = -> { ActiveAdmin.application.unload! }
-
-        if app.config.reload_classes_only_on_change
-          # Rails is about to unload all the app files (e.g. models), so we
-          # should first unload the classes generated by Active Admin, otherwise
-          # they will contain references to the stale (unloaded) classes.
-          ActiveSupport::Reloader.to_prepare(prepend: true, &unload_active_admin)
-        else
-          # If the user has configured the app to always reload app files after
-          # each request, so we should unload the generated classes too.
-          ActiveSupport::Reloader.to_complete(&unload_active_admin)
+        ActiveSupport::Reloader.after_class_unload do
+          ActiveAdmin.application.unload!
         end
 
         admin_dirs = {}

spec/integration/rails_integration_spec.rb

@@ -0,0 +1,13 @@
+require 'rails_helper'
+
+RSpec.describe 'Rails/ActiveAdmin integration' do
+  it 'unloads and reloads ActiveAdmin only once', :requires_reloading do
+    allow(ActiveAdmin.application).to receive(:unload!)
+    allow(ActiveAdmin.application).to receive(:load!)
+
+    Rails.application.reloader.reload!
+
+    expect(ActiveAdmin.application).to have_received(:unload!).once
+    expect(ActiveAdmin.application).to have_received(:load!).once
+  end
+end

spec/spec_helper.rb

@@ -3,7 +3,8 @@
 RSpec.configure do |config|
   config.disable_monkey_patching!
   config.filter_run focus: true
-  config.filter_run_excluding changes_filesystem: true
+  config.filter_run_excluding changes_filesystem: true,
+                              requires_reloading: true
   config.run_all_when_everything_filtered = true
   config.color = true
   config.order = :random

spec/support/simplecov_reload_env.rb

@@ -0,0 +1,5 @@
+if ENV["COVERAGE"] == "true"
+  require "simplecov"
+
+  SimpleCov.command_name "reload specs"
+end

spec/unit/application_spec.rb

@@ -9,7 +9,12 @@
   end
 
   describe "#prepare" do
-    before { application.prepare! }
+    before do
+      %i[run complete prepare class_unload].each do |event|
+        ActiveSupport::Reloader.reset_callbacks(event)
+      end
+      application.prepare!
+    end
 
     it "should remove app/admin from the autoload paths" do
       expect(ActiveSupport::Dependencies.autoload_paths).to_not include(Rails.root.join("app/admin"))

tasks/test.rake

@@ -12,7 +12,7 @@ task spec: :"spec:all"
 
 namespace :spec do
   desc "Run all specs"
-  task all: [:regular, :filesystem_changes]
+  task all: [:regular, :filesystem_changes, :reloading]
 
   desc "Run the standard specs in parallel"
   task :regular do
@@ -23,6 +23,11 @@ namespace :spec do
   task :filesystem_changes do
     sh({ "RSPEC_FILESYSTEM_CHANGES" => "true" }, "bin/rspec")
   end
+
+  desc "Run the specs that require reloading"
+  task :reloading do
+    sh({ "CLASS_RELOADING" => "true" }, "bin/rspec")
+  end
 end
 
 desc "Run the cucumber scenarios in parallel"