Hi there! Thanks for jumping in, I tested again and here's the result:
As you can see, there are two yarn installs being done somehow vs one in your tutorial. But again, I just used the exact same commands (Rails 6.0.1). It seems others are also wondering what's happening: github.com/harvard-lil/h2o/issues/744 and github.com/rails/webpacker/issues/405
I bet this is not an issue of the Ruby buildpack but more an issue of Rails. There's also maybe no issue but if so then I would love for you to explain to me what's going on maybe.
From my point of view it's easier for Rails to leave the whole "package.json dependencies installation" to the users rather than trying to be smart about it.
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