How to get Heroku to recognize a yarn.lock or package.json within a subdirectory (not root)

Question

I have a Rails application using React, Webpack, and Yarn for the client side. I have everything relating to the client side within the /client directory. This includes my yarn.lock and package.json files. I have a Procfile that cds into /client and properly runs yarn run build. This works locally with no errors. However, when I deploy/push to Heroku, my push is rejected and I get the following error:

remote:        cd client && yarn run build:production
remote:        sh: 1: yarn: not found
remote:        rake aborted!
remote:        Command failed with status (127): [cd client && yarn run build:production...]

What this says to me is that Heroku wasn't able to find a yarn.lock file in the root level. How do I get Heroku to use the yarn.lock file within my /client directory?

Or is the cause of this error something else entirely?

Answer 1

Make sure to use both ruby and node buildpacks. I got this error when I didn't.

Execute these in your root folder:

heroku buildpacks:set heroku/ruby
heroku buildpacks:add --index 1 heroku/nodejs

Sources: https://devcenter.heroku.com/articles/using-multiple-buildpacks-for-an-app

https://github.com/shakacode/react_on_rails/blob/master/docs/additional-reading/heroku-deployment.md

Answer 2

Just been through a similar thing myself. You need to order the buildpacks so that node is first. If a yarn.lock is in your root dir (or yarn is in your "engines" key as in @remydib's answer), then the node buildpack will install yarn and then your packages. If you have a yarn.lock in /client, put one in root, and add a postinstall script to it that says cd client && yarn run build.

In my case (rake assets:precompile calls yarn and fails), for some reason when the buildpacks go ruby -> node, Heroku doesn't wait for node to install before trying to run rake tasks, and we go kablooie.

Hope this helps.