New buildpack fails to run webpack command

[vincentwoo]

Post sprockets CVE, I have made only the following diff to my Rails app's production.rb:

   # Whether to fallback to assets pipeline if a precompiled asset is missed.
-  config.assets.compile = true
+  config.assets.compile = false

However, builds now seem to fail with this error:

remote:        Compiling…
remote:        Compilation failed:
remote:        error Command "webpack" not found.
remote:
remote:        yarn run v1.8.0
remote:        info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
remote:
remote:  !
remote:  !     Precompiling assets failed.
remote:  !
remote:  !     Push rejected, failed to compile Ruby app.
remote:
remote:  !     Push failed
remote: Verifying deploy...

Ironically, this is preventing us from deploying the relevant fix to Sprockets. Help would be urgently appreciated.

[vincentwoo]

I should add that we have the Node buildpack at #1, with Ruby at #2, and that our binstubs are present and have been working without issue on all previous successful deploys.

[schneems]

Thanks for opening the support ticket. It's much easier to diagnose these things with app logs.

If anyone else is seeing this try to replace heroku/ruby in your heroku buildpacks with https://github.com/heroku/heroku-buildpack-ruby#v186 which is the commit right before these changes went out. That will help determine if the latest buildpack deploy was the culprit.

Going to close this issue in favor of communicating over the support ticket. Sorry the app's not able to deploy right now, hopefully we'll get this resolved soon.