webpacker won't compile when pushing to Heroku - ruby-on-rails

Question

I've recently tried integrating react into my preexisting rails app by using the webpacker gem. When I try to push to heroku, I see the an error message like
remote: [1/5] Validating package.json...
remote: [2/5] Resolving packages...
remote: [3/5] Fetching packages...
remote: [4/5] Linking dependencies...
remote: [5/5] Building fresh packages...
remote: success Saved lockfile.
remote: Done in 0.09s.
remote: Compiling…
remote: Compilation failed:
remote: error Command "webpack" not found.
remote:
remote: yarn run v1.12.3
remote: info Visit https://yarnpkg.com/en/docs/cli/run for
documentation about this command.
remote:
remote:
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 spitball-production.
remote:
To https://git.heroku.com/spitball-production.git
! [remote rejected] master -> master (pre-receive hook declined)
My package.json looks like
{
"name": "Spitball",
"private": true,
"dependencies": {
},
"engines": {
"yarn": ">=0.25.2"
}
}
I've tried the solutions involving adding buildpacks and installing yarn and webpacker and so far nothing has helped. I'm expecting everything to push through no problem as all I've done is add the webpacker gem.

Answer 1

Did you try running
$ rails assets:precompile
in your terminal prior to pushing to Github then Heroku?
You have to compile all of your assets files prior to being built by Heroku.