Fallback to npm if yarn is not available

[dhh]

We default to yarn, and that's fine, but if you don't have that installed, it would be nice to fallback to npm.

[igas]

@dhh is there a specific reason for using yarn? My understanding as rails devs we wanted a lock file, but as npm supports that for a while it'll be good to avoid yarn if possible. It would be even cooler if we could avoid node altogether, as esbuild does not need it, but due to the wrapping in jsbundling-rails we'll still need node.

[turgs]

❤️ npm is available by default with Node these days, and is now backed with GitHub's ownership. yarn is an extra dependency that needs to be installed for no benefit over npm these days

Brief summary:
https://lalomartins.medium.com/in-2021-should-i-use-yarn-or-npm-f0659cb6a9c9

[phantomwhale]

Was this closed because "this should happen now" ? Or closed because it was decided not to implement this ?

Given all the good points made above for supporting npm in a yarn-free environment, I had presumed it should be the former, but looking over the documentation and trying it out, I'm starting to presume it's actually the latter.