Use lazy load hook to configure ActiveStorage::Blob

`to_prepare` callbacks are run during initialization; using one here
meant that `ActiveStorage::Blob` would be loaded when the app boots,
which would in turn load `ActiveRecord::Base`.

By using a lazy load hook to configure `ActiveStorage::Blob` instead,
we can avoid loading `ActiveRecord::Base` unnecessarily.

1 files changed, 12 insertions, 0 deletions

diff --git a/railties/test/application/loading_test.rb b/railties/test/application/loading_test.rb
index 2632dd7cde..889ad16fb8 100644
--- a/railties/test/application/loading_test.rb
+++ b/railties/test/application/loading_test.rb
@@ -359,6 +359,18 @@ class LoadingTest < ActiveSupport::TestCase
     assert_predicate Rails.application, :initialized?
   end
 
+  test "frameworks aren't loaded during initialization" do
+    app_file "config/initializers/raise_when_frameworks_load.rb", <<-RUBY
+      %i(action_controller action_mailer active_job active_record).each do |framework|
+        ActiveSupport.on_load(framework) { raise "\#{framework} loaded!" }
+      end
+    RUBY
+
+    assert_nothing_raised do
+      require "#{app_path}/config/environment"
+    end
+  end
+
   private
 
     def setup_ar!