Deployment instructions for Heroku apps potentially problematic

[andreas-venturini]

In the docs section about Heroku deployments it's recommended to include the Heroku nodejs buildpack.

However, this is potentially problematic as in Rails apps yarn install will again be run as part of the asset precompilation step if the yarn binstub is present (which is probably the case for the majority of Rails apps)

This leads to yarn install being executed twice, as described in this comment .

In the same issue one suggested workaround is to manually disable the yarn install rake task - I think this should be added as a disclaimer to the deployment docs section.

If this is an agreeable change I can send a PR.

[dwightwatson]

The ruby buildpack should now include Node for Webpacker out of the box, so is this necessary at all? Could we just remove the node buildpack recommendation from the docs?

[andreas-venturini]

The ruby buildpack should now include Node for Webpacker out of the box, so is this necessary at all

Technically it's not (at least not right now). However, I would advise against removing for two reasons:

1. with Yarn 2 the Ruby buildpack fails to prune dev dependencies which will increase the Heroku slug size. This is easy to miss as I imagine not everyone monitors their slug size.
2. the current Ruby buildpack seems deprecated and will be replaced w/ a Cloud Native Buildpack that explicitly requires node to be installed via the heroku/nodejs buildpack.

[justin808]

@guillaumebriday I made a small update here: https://github.com/rails/webpacker/pull/3231/files

@andreas-venturini Would be great if you can submit a PR with som add some additional details regarding the duplicate yarn install.

@dwightwatson I think having both the ruby and node buildpacks makes logical sense for Heroku applications using webpack.

[guillaumebriday]

Great! I'm pretty sure we can close this issue right?

[justin808]

@guillaumebriday, yes, I think so. In the future, somebody can open up a more specific issue with a problem and maybe a proposed solution.

While I think it's suboptimal for yarn to run twice with Heroku, it runs quite fast the second time, so it's not a huge issue.