Having trouble deploying my rails app to heroku “Error: Cannot find module '@rails/webpacker'”

Question

I'm working on a rails app that uses webpack and babel to handle the JavaScript I've incorporated and every time I try to deploy to heroku I get this error "Error: Cannot find module '@rails/webpacker'". I've verified that webpacker is installed and included in my Gemfile and have even tried updating. I'm not sure what else could be wrong and I wasn't able to find a fix on here or in the heroku troubleshooting. Here's what the error looks like:

remote:        Webpacker is installed 🎉 🍰
remote:        Using /tmp/build_8b49575f969275dcaa6d475e06d48642/config/webpacker.yml file for setting up webpack paths
remote:        Compiling…
remote:        Compilation failed:
remote:        module.js:540
remote:        throw err;
remote:        ^
remote:        Error: Cannot find module '@rails/webpacker'
remote:        at Function.Module._resolveFilename (module.js:538:15)
remote:        at Function.Module._load (module.js:468:25)
remote:        at Module.require (module.js:587:17)
remote:        at require (internal/module.js:11:18)

remote:        at Object.<anonymous> (/tmp/build_8b49575f969275dcaa6d475e06d48642/config/webpack/environment.js:1:87)
remote:        at Module._compile (module.js:643:30)
remote:        at Object.Module._extensions..js (module.js:654:10)
remote:        at Module.load (module.js:556:32)
remote:        at tryModuleLoad (module.js:499:12)
remote:        at Function.Module._load (module.js:491:3)
remote:  !
remote:  !     Precompiling assets failed.
remote:  !
remote:  !     Push rejected, failed to compile Ruby app.
remote:
remote:  !     Push failed
remote: Verifying deploy...
remote:
remote: !       Push rejected to guarded-falls-58657.
remote:
To https://git.heroku.com/guarded-falls-58657.git
! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/guarded-falls-
58657.git'

Answer 1

Would you try this?

heroku buildpacks:clear
heroku buildpacks:set heroku/nodejs
heroku buildpacks:add heroku/ruby

https://github.com/rails/webpacker/issues/739#issuecomment-327546884

It seems that the Ruby default buildpack has some outdated node-related engines. Should be fixed soon hopefully.