Companion heroku deployment broken

[mifi]

Heroku deploy fails: https://github.com/transloadit/uppy/runs/4473760891?check_suite_focus=true

I believe this is because it tries to do npm install inside the companion subdirectory, and it will use the wrong version of @types/redis and crashes.

See also #3355

While heroku does support yarn install, there are some issues:

• yarn install needs to be done from the root dir
• must use "heroku-postbuild": "cd packages/@uppy/companion && yarn run build" inside monorepo root package.json as by default heroku will call npm run build.
• should only yarn install companion workspace and not the whole uppy repo, as it will take a lot more time
• heroku doesn't seem to support yarn workspaces focus

Alternative: Use docker

https://devcenter.heroku.com/articles/build-docker-images-heroku-yml

I tried in this branch https://github.com/transloadit/uppy/tree/fix-heroku-yarn and it almost worked, but experienced these issues:

• COMPANION_DATADIR cannot be ./out.
  • Setting it to /tmp seemed to fix that
• apparently all heroku servers need to listen to the heroku-assigned environment variable PORT. So it cannot listen to 3020.
  • I got this error: Error R10 (Boot timeout) -> Web process failed to bind to $PORT within 60 seconds of
  • heroku doesn't support EXPOSE so we may need to change the docker file