Yarn will now be installed for Ruby applications that have a `yarn.lock` file

Change effective on 27 October 2021

Ruby applications using the heroku/ruby buildpack now receive a default version of yarn installed if they have a yarn.lock file in the root directory of their application.

Prior to this change, only applications using the webpacker gem would trigger node installation logic. This change is intended to facilitate Rails 7 applications using jsbundling-rails without webpacker.

Note Applications using the heroku/nodejs buildpack before the heroku/ruby buildpack will not see a change in behavior

For more information, see Heroku Ruby support documentation.