`gem update --system` does not respect RubyGems constraints on current ruby

[nevans]

Describe the problem as clearly as you can

gem update --system fails on ruby 2.7, or at least on ruby 2.7 as installed by ruby/setup-ruby. Specifically, this is causing CI failures for gems that still support older rubies.

See e.g: https://github.com/ruby/net-imap/actions/runs/7273131765/job/19916818198?pr=251

Did you try upgrading RubyGems?

This is, in fact, the problem. 😉

Post steps to reproduce the problem

I assume this is happening for other gems supporting older versions of ruby as well. The workflow file is fairly standard.

- name: Set up Ruby
      uses: ruby/setup-ruby@v1
      with:
        ruby-version: ${{ matrix.ruby }}
        bundler-cache: true
        rubygems: latest

Which command did you run?

/opt/hostedtoolcache/Ruby/2.7.8/x64/bin/gem --version
  3.1.6
  Default RubyGems version is 3.1.6
  Updating RubyGems to latest version
 
/opt/hostedtoolcache/Ruby/2.7.8/x64/bin/gem update --system
  ERROR:  Error installing rubygems-update:
  	There are no versions of rubygems-update (= 3.5.3) compatible with your Ruby & RubyGems
  	rubygems-update requires Ruby version >= 3.0.0. The current ruby version is 2.7.8.[22](https://github.com/ruby/net-imap/actions/runs/7273131765/job/19916818198?pr=251#step:3:27)5.
  ERROR:  While executing gem ... (NoMethodError)
      undefined method `version' for nil:NilClass
  Updating rubygems-update
  Took  14.85 seconds
Error: The process '/opt/hostedtoolcache/Ruby/2.7.8/x64/bin/gem' failed with exit code 1

What were you expecting to happen?

The latest (compatible) version would be installed.

What actually happened?

The command failed.

Misc

Perhaps this is related to #7310? For purposes of passing CI, the simple workaround is to set a version constraint rather than use latest. Still, it would be nice if that were unnecessary. 🙂

[simi]

@nevans hello, this is known problem and could be fixed as mentioned. There is plan to make gem update update to latest working version, but sadly it wouldn't be able to fix this in older versions.

[deivid-rodriguez]

This was fixed by #4110, which was released with RubyGems 3.2.3. Unfortunately not much we can do for users of older rubies that don't come with a RubyGems version that includes the fix, but should be ok from now on since Ruby 3.0 already incles RubyGems 3.2.3.

[MSP-Greg]

This is a bug in older versions of RubyGems, but a workaround for GHA (setup-ruby) has been proposed.

See ruby/setup-ruby#551

[deivid-rodriguez]

Good catch @MSP-Greg. Indeed there's something that can be done to workaround this in ruby/setup-ruby, thanks for working on that!

[simi]

This was fixed by #4110, which was released with RubyGems 3.2.3. Unfortunately not much we can do for users of older rubies that don't come with a RubyGems version that includes the fix, but should be ok from now on since Ruby 3.0 already incles RubyGems 3.2.3.

Are you 100% sure? Per my understanding gem update --system doesn't use gem install or gem update internally sadly.

[retro@retro  tmp]❤ ruby -v
ruby 2.7.4p191 (2021-07-07 revision a21a3b7d23) [x86_64-linux]
[retro@retro  tmp]❤ gem -v
3.2.4
[retro@retro  tmp]❤ gem update --system
Updating rubygems-update
ERROR:  Error installing rubygems-update:
        rubygems-update-3.5.3 requires Ruby version >= 3.0.0. The current ruby version is 2.7.4.191.
Installing RubyGems 3.2.4
  Successfully built RubyGem
  Name: bundler
  Version: 2.2.4
  File: bundler-2.2.4.gem
Bundler 2.2.4 installed
RubyGems 3.2.4 installed
Regenerating binstubs
Regenerating plugins



------------------------------------------------------------------------------

RubyGems installed the following executables:
        /home/retro/.rubies/ruby-2.7.4/bin/gem
        /home/retro/.rubies/ruby-2.7.4/bin/bundle

RubyGems system software updated

[MSP-Greg]

Question - What is the likelihood of updates to RG 3.3.x and 3.4.x?

If they have patch updates, the code in setup-ruby should also be updated. That's the 'brittle' I referred to in the PR notes.

I looked for a doc stating policy, couldn't find one. I probably missed it. Of course, it's "maintainer's choice", but wasn't sure about backports, CVE's, etc.

[deivid-rodriguez]

You're right @simi, my bad!