Insure yarn is installed before running the install template. about webpacker

[nicolasblanco]

Hello, I don't understand the issue there :).

You did not have yarn installed and got a nice error message when the script tried to run it,
what do you want to change exactly?

IMHO, It's not really the current philosophy to put a pile of tests trying to detect all possible missing file or command before actually running the script.
There would be thousands of possible failures for each command.

[jcoyne]

@nicolasblanco I'm positing that a good error message tells the user what they did wrong (done) and what they should do now (missing). It should say "go install yarn and then run bin/rails webpacker:install again"

[dhh]

This gem isn't currently designed with much intent for 5.0.1. It's intended target is 5.1, where Yarn is available by default. But feel free to submit a PR with a proposal for a different error message.