1 files changed, 66 insertions, 0 deletions
diff --git a/railties/lib/rails/tasks/zeitwerk.rake b/railties/lib/rails/tasks/zeitwerk.rake
new file mode 100644
index 0000000000..5421af6e8b
--- /dev/null
+++ b/railties/lib/rails/tasks/zeitwerk.rake
@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+ensure_zeitwerk_mode = ->() do
+  unless Rails.autoloaders.zeitwerk_enabled?
+    abort "Please, enable :zeitwerk mode in config/application.rb and try again."
+  end
+end
+
+eager_load = ->() do
+  puts "Hold on, I am eager loading the application."
+  Zeitwerk::Loader.eager_load_all
+end
+
+report_not_checked = ->(not_checked) do
+  puts
+  puts <<~EOS
+    WARNING: The files in these directories cannot be checked because they
+    are not eager loaded:
+  EOS
+  puts
+
+  not_checked.each { |dir| puts "  #{dir}" }
+  puts
+
+  puts <<~EOS
+    You may verify them manually, or add them to config.eager_load_paths
+    in config/application.rb and run zeitwerk:check again.
+  EOS
+  puts
+end
+
+report = ->(not_checked) do
+  if not_checked.any?
+    report_not_checked[not_checked]
+    puts "Otherwise, all is good!"
+  else
+    puts "All is good!"
+  end
+end
+
+namespace :zeitwerk do
+  desc "Checks project structure for Zeitwerk compatibility"
+  task check: :environment do
+    ensure_zeitwerk_mode[]
+
+    begin
+      eager_load[]
+    rescue NameError => e
+      if e.message =~ /expected file .*? to define constant \S+/
+        abort $&.sub(/#{Regexp.escape(Rails.root.to_s)}./, "")
+      else
+        raise
+      end
+    end
+
+    eager_load_paths = Rails.configuration.eager_load_namespaces.map do |eln|
+      eln.config.eager_load_paths if eln.respond_to?(:config)
+    end.compact.flatten
+
+    not_checked = ActiveSupport::Dependencies.autoload_paths - eager_load_paths
+    not_checked.select! { |dir| Dir.exist?(dir) }
+    not_checked.reject! { |dir| Dir.empty?(dir) }
+
+    report[not_checked]
+  end
+end