Only require the necessary Rails frameworks

By requiring rails/all Solidus was loading a bunch of unnecessary code
taking more time and consuming more memory. This change allows apps
that want to cherry-pick Rails frameworks to benefit from the more
attentive choice.

backend/lib/spree/backend.rb

@@ -1,6 +1,9 @@
 # frozen_string_literal: true
 
-require 'rails/all'
+require "active_record/railtie"
+require "action_view/railtie"
+require "sprockets/railtie"
+
 require 'jquery-rails'
 require 'coffee-rails'
 require 'sassc-rails'

backend/spec/lib/spree/backend_spec.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'spree/backend'
+
+RSpec.describe Spree::Backend do
+  it 'loads only the necessary Rails Frameworks' do
+    aggregate_failures do
+      expect(defined? ActionCable::Engine).to be_falsey
+      expect(defined? ActionController::Railtie).to be_truthy
+      expect(defined? ActionMailer::Railtie).to be_truthy
+      expect(defined? ActionView::Railtie).to be_truthy
+      expect(defined? ActiveJob::Railtie).to be_truthy
+      expect(defined? ActiveModel::Railtie).to be_truthy
+      expect(defined? ActiveRecord::Railtie).to be_truthy
+      expect(defined? ActiveStorage::Engine).to be_falsey
+      expect(defined? Rails::TestUnit::Railtie).to be_falsey
+      expect(defined? Sprockets::Railtie).to be_truthy
+    end
+  end
+end

core/lib/spree/core.rb

@@ -1,6 +1,13 @@
 # frozen_string_literal: true
 
-require 'rails/all'
+require "active_model/railtie"
+require "active_job/railtie"
+require "active_record/railtie"
+require "action_controller/railtie"
+require "action_mailer/railtie"
+require "action_view/railtie"
+require "sprockets/railtie"
+
 require 'acts_as_list'
 require 'awesome_nested_set'
 require 'cancan'

core/lib/spree/testing_support/dummy_app.rb

@@ -7,6 +7,7 @@
 require 'active_record/railtie'
 require 'action_controller/railtie'
 require 'action_mailer/railtie'
+require 'active_storage/engine'
 
 Rails.env = 'test'
 

core/spec/lib/spree/core_spec.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'spree/core'
+
+RSpec.describe Spree::Core do
+  it 'loads only the necessary Rails Frameworks' do
+    aggregate_failures do
+      expect(defined? ActionCable::Engine).to be_falsey
+      expect(defined? ActionController::Railtie).to be_truthy
+      expect(defined? ActionMailer::Railtie).to be_truthy
+      expect(defined? ActionView::Railtie).to be_truthy
+      expect(defined? ActiveJob::Railtie).to be_truthy
+      expect(defined? ActiveModel::Railtie).to be_truthy
+      expect(defined? ActiveRecord::Railtie).to be_truthy
+      expect(defined? ActiveStorage::Engine).to be_truthy
+      expect(defined? Rails::TestUnit::Railtie).to be_falsey
+      expect(defined? Sprockets::Railtie).to be_truthy
+    end
+  end
+end

frontend/lib/spree/frontend.rb

@@ -1,6 +1,10 @@
 # frozen_string_literal: true
 
-require 'rails/all'
+require "active_record/railtie"
+require "action_controller/railtie"
+require "action_view/railtie"
+require "sprockets/railtie"
+
 require 'jquery-rails'
 require 'canonical-rails'
 require 'sassc-rails'

frontend/spec/lib/spree/frontend_spec.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'spree/frontend'
+
+RSpec.describe Spree::Frontend do
+  it 'loads only the necessary Rails Frameworks' do
+    aggregate_failures do
+      expect(defined? ActionCable::Engine).to be_falsey
+      expect(defined? ActionController::Railtie).to be_truthy
+      expect(defined? ActionMailer::Railtie).to be_truthy
+      expect(defined? ActionView::Railtie).to be_truthy
+      expect(defined? ActiveJob::Railtie).to be_truthy
+      expect(defined? ActiveModel::Railtie).to be_truthy
+      expect(defined? ActiveRecord::Railtie).to be_truthy
+      expect(defined? ActiveStorage::Engine).to be_falsey
+      expect(defined? Rails::TestUnit::Railtie).to be_falsey
+      expect(defined? Sprockets::Railtie).to be_truthy
+    end
+  end
+end