Rails 6: enable zeitwerk autoloader (#8766)

* More loading fixes

* Go back to OpenStruct

* Shuffle things around

* Remove obsolete patches and unneeded requires

* Disable config.add_autoload_paths_to_load_path

* Fix pre-require errors

* Config not reloader

app/liquid_tags/github_tag/github_readme_tag.rb

@@ -1,5 +1,3 @@
-require "nokogiri"
-
 class GithubTag
   class GithubReadmeTag
     PARTIAL = "liquids/github_readme".freeze

app/liquid_tags/glitch_tag.rb

@@ -1,5 +1,3 @@
-require "uri"
-
 class GlitchTag < LiquidTagBase
   attr_accessor :uri
 

app/services/authentication/providers.rb

@@ -1,10 +1,3 @@
-# We require all authentication modules to make sure providers
-# are correctly preloaded both in development and in production and
-# ready to be used when needed at runtime
-Dir[Rails.root.join("app/services/authentication/**/*.rb")].each do |f|
-  require_dependency(f)
-end
-
 module Authentication
   module Providers
     # Retrieves a provider that is both available and enabled

app/services/aws/fake_client.rb

@@ -1,8 +0,0 @@
-# Fake Aws client is used in non-production environments to prevent actual calls to AWS lambda
-module Aws
-  class FakeClient
-    def invoke(*)
-      OpenStruct.new(payload: [{ body: { message: 0 }.to_json }.to_json])
-    end
-  end
-end

config/application.rb

@@ -22,22 +22,25 @@ module PracticalDeveloper
     # Initialize configuration defaults for originally generated Rails version.
     config.load_defaults 5.1 # NOTE: [Rails 6] we should at least work towards updating this to 5.2
 
+    # [Rails 6] Zeitwerk is the new autoloader
+    # As we don't have `load_defaults 6.0` yet, it has to be enabled manually
+    # See <https://guides.rubyonrails.org/autoloading_and_reloading_constants.html>
+    config.autoloader = :zeitwerk
+
+    # Disable auto adding of default load paths to $LOAD_PATH
+    # Setting this to false saves Ruby from checking these directories when
+    # resolving require calls with relative paths, and saves Bootsnap work and
+    # RAM, since it does not need to build an index for them.
+    # see https://github.com/rails/rails/blob/6-0-stable/railties/CHANGELOG.md#rails-600rc2-july-22-2019
+    config.add_autoload_paths_to_load_path = false
+
     # Settings in config/environments/* take precedence over those specified here.
     # Application configuration can go into files in config/initializers
     # -- all .rb files in that directory are automatically loaded after loading
     # the framework and any gems in your application.
 
-    config.autoload_paths += Dir["#{config.root}/app/labor/"]
-    config.autoload_paths += Dir["#{config.root}/app/decorators/"]
-    config.autoload_paths += Dir["#{config.root}/app/services/"]
-    config.autoload_paths += Dir["#{config.root}/app/presenters/"]
-    config.autoload_paths += Dir["#{config.root}/app/liquid_tags/"]
-    config.autoload_paths += Dir["#{config.root}/app/black_box/"]
-    config.autoload_paths += Dir["#{config.root}/app/sanitizers"]
-    config.autoload_paths += Dir["#{config.root}/app/facades"]
-    config.autoload_paths += Dir["#{config.root}/app/errors"]
-    config.autoload_paths += Dir["#{config.root}/app/view_objects"]
-    config.autoload_paths += Dir["#{config.root}/lib/"]
+    config.autoload_paths += Dir["#{config.root}/lib"]
+    config.eager_load_paths += Dir["#{config.root}/lib"]
 
     config.active_job.queue_adapter = :sidekiq
 

config/environment.rb

@@ -3,5 +3,3 @@ require_relative "application"
 
 # Initialize the Rails application.
 Rails.application.initialize!
-
-require "carrierwave/orm/activerecord"

config/initializers/authentication.rb

@@ -0,0 +1,8 @@
+Rails.application.config.to_prepare do
+  # We require all authentication modules to make sure providers
+  # are correctly preloaded and ready to be used at this point as the loading
+  # order is important
+  Dir[Rails.root.join("app/services/authentication/**/*.rb")].each do |f|
+    require_dependency(f)
+  end
+end

config/initializers/aws_sdk.rb

@@ -1,9 +1,18 @@
-AWS_LAMBDA = if Rails.env.production?
-               Aws::Lambda::Client.new(
-                 region: ApplicationConfig["AWS_DEFAULT_REGION"],
-                 access_key_id: ApplicationConfig["AWS_SDK_KEY"],
-                 secret_access_key: ApplicationConfig["AWS_SDK_SECRET"],
-               )
-             else
-               Aws::FakeClient.new
-             end
+Rails.application.reloader.to_prepare do
+  AWS_LAMBDA = if Rails.env.production?
+                 Aws::Lambda::Client.new(
+                   region: ApplicationConfig["AWS_DEFAULT_REGION"],
+                   access_key_id: ApplicationConfig["AWS_SDK_KEY"],
+                   secret_access_key: ApplicationConfig["AWS_SDK_SECRET"],
+                 )
+               else
+                 # Fake Aws::Lambda::Client
+                 Class.new do
+                   def invoke(*)
+                     # rubocop:disable Performance/OpenStruct
+                     OpenStruct.new(payload: [{ body: { message: 0 }.to_json }.to_json])
+                     # rubocop:enable Performance/OpenStruct
+                   end
+                 end.new
+               end
+end

config/initializers/datadog_apm.rb

@@ -1,6 +1,3 @@
-require "ddtrace"
-require "datadog/statsd"
-
 Datadog.configure do |c|
   c.tracer env: Rails.env
   c.tracer enabled: Rails.env.production?

config/initializers/liquid.rb

@@ -1,14 +1,13 @@
-# TODO: [rhymes] [Rails 6] explicitly requiring dependencies in `classic` mode.
-# Will move over to `zeitwerk` in a future PR
-Dir.glob(Rails.root.join("lib/liquid/*.rb")).sort.each do |filename|
-  require_dependency filename
-end
-
-# Our custom Liquid tags are registered to Liquid::Template at the bottom of
-# each files. Each Liquid tags will need to be loaded/required before the main
-# Liquid gem is evoked, hence the need for the fix below.
-
 Rails.application.config.to_prepare do
+  # Explicitly requiring lib/liquid to make sure that our patches are loaded
+  # before liquid tags are loaded
+  Dir.glob(Rails.root.join("lib/liquid/*.rb")).sort.each do |filename|
+    require_dependency filename
+  end
+
+  # Our custom Liquid tags are registered to Liquid::Template at the bottom of
+  # each files. Each Liquid tags will need to be loaded/required before the main
+  # Liquid gem is evoked, hence the need to pre-require them in order
   Dir.glob(Rails.root.join("app/liquid_tags/*.rb")).sort.each do |filename|
     require_dependency filename
   end

config/initializers/pusher.rb

@@ -1,4 +1,3 @@
-require "pusher"
 require "pusher/push_notifications"
 
 Pusher.app_id = ApplicationConfig["PUSHER_APP_ID"]

config/initializers/reverse_markdown.rb

@@ -1,13 +0,0 @@
-# This eagerload our custom ReverseMarkdown::Converters and allows it to be autoreloaded
-# in development.
-#
-# Because files are eagerloaded in production, this fix is only
-# applicable in development (and test, when needed)
-
-if Rails.env.development? || Rails.env.test?
-  Rails.application.config.to_prepare do
-    Dir.glob(Rails.root.join("app/lib/reverse_markdown/converters/*.rb")).sort.each do |filename|
-      require_dependency filename
-    end
-  end
-end

config/initializers/sidekiq.rb

@@ -1,22 +1,9 @@
-# Monkey patch `stringify_keys` to make rack 2.1.1 compatible with Sidekiq UI Admin panel.
-# Should be removed when 2.1.2 is released.
-# https://github.com/rack/rack/pull/1428
-module Rack
-  module Session
-    module Abstract
-      class SessionHash
-        private
-
-        def stringify_keys(other)
-          other.to_hash.transform_keys(&:to_s)
-        end
-      end
-    end
+Rails.application.config.to_prepare do
+  Dir.glob(Rails.root.join("lib/sidekiq/*.rb")).sort.each do |filename|
+    require_dependency filename
   end
 end
 
-require Rails.root.join("lib/sidekiq/worker_retries_exhausted_reporter")
-
 Sidekiq.configure_server do |config|
   sidekiq_url = ApplicationConfig["REDIS_SIDEKIQ_URL"] || ApplicationConfig["REDIS_URL"]
   # On Heroku this configuration is overridden and Sidekiq will point at the redis

config/initializers/zeitwerk.rb

@@ -0,0 +1,15 @@
+# Zeitwerk (Rails 6+) autoloader
+# see https://guides.rubyonrails.org/autoloading_and_reloading_constants.html
+
+# Configures default inflections for the zeitwerk autoloader
+# see <https://guides.rubyonrails.org/autoloading_and_reloading_constants.html#customizing-inflections>
+Rails.autoloaders.each do |autoloader|
+  autoloader.inflector.inflect(
+    "html_rouge" => "HTMLRouge",
+    "url" => "URL",
+  )
+end
+
+# Ignoring folders that don't adhere to the new naming conventions
+Rails.autoloaders.main.ignore(Rails.root.join("lib/data_update_scripts"))
+Rails.autoloaders.main.ignore(Rails.root.join("lib/generators/data_update"))

spec/lib/liquid/raw_spec.rb

@@ -1,8 +1,20 @@
 require "rails_helper"
 
-RSpec.describe Liquid::Raw do
+RSpec.describe Liquid::Raw, type: :lib do
   it "uses the correct regexp for invalid tokens" do
     expected_regexp = /\A(.*)#{Liquid::TagStart}\s*(\w+)\s*#{Liquid::TagEnd}\z/om
     expect(described_class::FullTokenPossiblyInvalid).to eq(expected_regexp)
   end
+
+  it "does not allow non whitespace characters in between the tags" do
+    invalid_markdown = '<img src="x" class="before{% raw %}inside{% endraw ">%}rawafter"onerror=alert(document.domain) '
+    expect { Liquid::Template.parse(invalid_markdown) }.to raise_error(StandardError)
+  end
+
+  it "raise error message when link tag contain non article URL" do
+    invalid_markdown = "{% link /some-random-link/ %}"
+    expect { Liquid::Template.parse(invalid_markdown) }.to(
+      raise_error(StandardError, "This URL is not an article link: {% link /some-random-link/ %}"),
+    )
+  end
 end

spec/lib/liquid/variable_spec.rb

@@ -1,6 +1,6 @@
 require "rails_helper"
 
-RSpec.describe Liquid::Variable do
+RSpec.describe Liquid::Variable, type: :lib do
   it "does not allow instantiation" do
     expect { described_class.new("", nil) }.to raise_error(StandardError, /variables are disabled/)
   end

spec/liquid_tags/liquid/raw_spec.rb

@@ -1,15 +0,0 @@
-require "rails_helper"
-
-RSpec.describe Liquid::Raw, type: :liquid_tag do
-  it "does not allow non whitespace characters in between the tags" do
-    invalid_markdown = '<img src="x" class="before{% raw %}inside{% endraw ">%}rawafter"onerror=alert(document.domain) '
-    expect { Liquid::Template.parse(invalid_markdown) }.to raise_error(StandardError)
-  end
-
-  it "raise error message when link tag contain non article URL" do
-    invalid_markdown = "{% link /some-random-link/ %}"
-    expect { Liquid::Template.parse(invalid_markdown) }.to(
-      raise_error(StandardError, "This URL is not an article link: {% link /some-random-link/ %}"),
-    )
-  end
-end