Heroku deployment fails with rake task error starting in commit #421

[reconstructions]

Starting in commit #421, webpack asset precompilation fails with the following error when pushing to Heroku:

remote:        [10] ./~/ieee754/index.js 2.05 kB {0} [built]
remote:        [11] ./~/isarray/index.js 132 bytes {0} [built]
remote:        [12] (webpack)/buildin/global.js 509 bytes {0} [built]
error Command failed with exit code 2.
remote:        info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
remote:        error Command failed with exit code 1.
remote:        info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
remote:        rake aborted!
remote:        Command failed with status (1): [cd client && yarn run build:production...]
remote:        /tmp/build_68aa8556fbac497714a17044a8dedc53/vendor/bundle/ruby/2.4.0/gems/react_on_rails-10.0.0/lib/tasks/assets.rake:64:in `block (3 levels) in <top (required)>'
remote:        /tmp/build_68aa8556fbac497714a17044a8dedc53/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/exe/rake:27:in `<top (required)>'
remote:        Tasks: TOP => assets:precompile => react_on_rails:assets:compile_environment => react_on_rails:assets:webpack

I get the same error pushing commits #424, #425, and #426. Commits #416 and earlier push with no problem.

I will try to figure out what the breaking change was.

[reconstructions]

If I change commit #416 to use the engine specs from the commit #421 package.json, pushing to Heroku fails this way. If I rollback all the changes made since commit #416 in commit #426, that fixes it. I've tried each option a couple times.

[reconstructions]

I made a PR which fixes pushing to Heroku by rolling Yarn back to version 0.22.0. The only other lines which need to be rolled back to #416 are bits of syntax in the client/package.json scripts.

There are a bunch of issues with proposed solutions to similar errors, but it looks like they could have different causes and none of them worked here. It is also unclear whether this is really a webpacker, yarn, heroku, or react_on_rails issue:

webpacker#821
webpacker#530
webpacker#915
heroku-buildpack-ruby#610

I will follow up and see if I can figure anything out by looking more closely at how the react_on_rails gem is is working with yarn 1.3.2 on Heroku.