It's `Rails.application.executor.wrap` that is responsible for
clearing request/job local state such as `CurrentAttributes`.
Instead of including an ad hoc helper to clear `CurrentAttributes` it's
better to run the executor so we properly clear other states as well.
However it means all executor hooks now need to be re-entrant.
This updates ActionView::CacheExpiry to hold a lock while inside the
executor (ie. inside a request) and to only clear caches when that is
done.
This is done using Concurrent::ReadWriteLock. This allows any number
of parallel requests to hold the read lock, but once we detect a change
and begin to acquire the write lock, all future requests will be
blocked.
Currently, `clear_cache_if_necessary` is executed even if view paths are
not set like `rails console`.
If the watcher class is `EventedFileUpdateChecker` and the watch
directories are empty, the application root directory will watch. This
is because listen uses the current directory as the default watch directory.
8d85b4cd57/lib/listen/adapter/config.rb (L13)
As a result, `node_modules` also watch. This cause a warning of `listen`.
Ref: https://github.com/rails/rails/pull/36377#issuecomment-498399576
Jean Boussier