ruby-install depends on xzcat, which is not available out of the box on all platforms

[monfresh]

Description

I maintain a script that installs Ruby on a Mac. If Homebrew is not yet present on the machine, the script installs Homebrew, then installs chruby and ruby-install, then installs the latest Ruby with ruby-install. Up until the latest xzcat changes in 0.8.4, it was working perfectly. But now, on a machine that didn't have Homebrew prior to running my script, the Ruby compilation fails with:

xzcat: command not found

Instead of assuming xzcat is in the PATH, would it be better to use the full path using the brew prefix, like $(brew --prefix)/xzcat?

cc @jmettraux

[monfresh]

I originally thought that xzcat was installed by Homebrew because when I do which xzcat, it shows me /usr/local/bin/xzcat on Intel Macs and /opt/homebrew/bin/xzcat on Apple Silicon Macs. However, it seems like that might only be the case on certain macOS versions. I have an Intel Mac on Big Sur, and after installing Homebrew and restarting the terminal, xzcat is still not found. So, I don't think it's a good idea to assume it's available everywhere.

[jmettraux]

So, I don't think it's a good idea to assume it's available everywhere.

Since you install Homebrew, can you brew install xzcat right before installing ruby-install?

If it's too much of a hassle, I'm totally OK with my change being reverted, since OpenBSD usage compared to MacOSX usage is tiny.

[monfresh]

OK, I found the issue. The reason why xzcat was available on my other machines, but not the Big Sur one is because I had somehow installed xz with Homebrew, probably as a dependency of another tool I installed. So, I can confirm that xzcat is NOT available by default on a Mac.

As for my script, I can fix this by adding xz (not xzcat because that formula doesn't exist on Homebrew) to my script's Brewfile.

[jmettraux]

https://github.com/postmodern/ruby-install/blob/master/.github/workflows/shunit2.yml

[monfresh]

Yeah, the macOS images from GitHub don't simulate a brand new Mac. They already come with a bunch of stuff installed on them, so this type of bug won't be found there. Here's what's included:

https://github.com/actions/virtual-environments/blob/macOS-11/20220710.1/images/macos/macos-11-Readme.md

It installs zstd, which depends on xz, which is why xzcat is available on that image.

[postmodern]

We can add xz as a dependency to the homebrew formula.

[monfresh]

@postmodern Yes, please. That seems like a great solution.

[postmodern]

xz is now a proper dependency of chruby. I assume homebrew should have synchronized chruby's homebrew formula into their repository automatically by now? Or do I have to tag a new release? I haven't kept up to speed with how homebrew updates their formulas; we used to have to manually submit a PR to them each time.

[monfresh]

Thanks! It doesn't look like Homebrew automatically synchronizes. When I run brew info ruby-install, I still see version 0.8.4 and it doesn't list any dependencies. I've never released anything on Homebrew so I'm not sure what the process is now.

[postmodern]

Hmm, guess I'll have to release 0.8.4.1 with the added dependency to get it updated in homebrew; not sure if adding a missing dependency warrants 0.8.5.

[eregon]

not sure if adding a missing dependency warrants 0.8.5.

IMHO yes, adding the missing dependency is a bug fix and deserves a patch release. Regarding Homebrew I think a PR is needed to https://github.com/Homebrew/homebrew-core/pulls

[mattmaddux]

FYI, for anyone needing to install before that PR is done, the brew package is xz not xzcat.

So just run

brew install xz

before running

ruby-install ruby

[afturner]

@postmodern would you be able to create the 0.8.5 tag? I can create a Homebrew PR if you'd like.

[postmodern]

OK ruby-install 0.8.5 has now been tagged and ruby-install's own copy of its homebrew formula has been updated. Hopefully, homebrew will automatically copy in the updated homebrew formula with the xz dependency.

[monfresh]

It looks like Homebrew didn't pick up the depends_on "xz" part. Here's the formula that's on Homebrew right now for version 0.8.5: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/ruby-install.rb

[postmodern]

I submitted a PR to homebrew to update their formula.

[monfresh]

Awesome. Thanks! After a brew update and brew info ruby-install, I can see the dependency listed now.