Bug #21954: NoMethodError instead of Gem::LoadError on gem activation problem in Ruby 4.0.2

• Status: Closed
• Assignee: hsbt (Hiroshi SHIBATA)
• Target version: -
• ruby -v: ruby 4.0.2 (2026-03-17 revision d3da9fec82) +PRISM [x86_64-linux]
• Backport: 3.2: DONTNEED, 3.3: DONTNEED, 3.4: DONTNEED, 4.0: REQUIRED

[jeremyevans0 (Jeremy Evans)]

I'm seeing a regression in Ruby 4.0.2 when there is a gem activation problem.

Install two versions of a gem, where one version has a file the other doesn't. One example here is rack:

$ gem install rack --version '< 3'
$ gem install rack

Force activation of the version that doesn't have the file, and then require the file and rescue LoadError:

gem 'rack', '< 3'

begin
  require 'rack/headers'
rescue LoadError
end

In previous versions of Ruby, the Gem::LoadError would be correctly rescued, and you would get no output. In Ruby 4.0.2, you get a NoMethodError raised:

/usr/local/lib/ruby/4.0/rubygems.rb:196:in 'Gem.try_activate': undefined method 'name' for nil (NoMethodError)

      spec ||= Gem::Specification.find_by_name(spec.name)
                                                   ^^^^^
        from /home/jeremy/gem-activate-problem.rb:4:in 'Kernel#require'
        from /home/jeremy/gem-activate-problem.rb:4:in '<main>'
/usr/local/lib/ruby/4.0/rubygems/specification.rb:2170:in 'Gem::Specification#check_version_conflict': can't activate rack-3.2.4, already activated rack-2.2.21 (Gem::LoadError)
        from /usr/local/lib/ruby/4.0/rubygems/specification.rb:1379:in 'Gem::Specification#activate'
        from /usr/local/lib/ruby/4.0/rubygems.rb:193:in 'Gem.try_activate'
        from /home/jeremy/gem-activate-problem.rb:4:in 'Kernel#require'
        from /home/jeremy/gem-activate-problem.rb:4:in '<main>'
/home/jeremy/gem-activate-problem.rb:4:in 'Kernel#require': cannot load such file -- rack/headers (LoadError)
        from /home/jeremy/gem-activate-problem.rb:4:in '<main>'

Same behavior on both OpenBSD and Linux.

[hsbt (Hiroshi SHIBATA)]

• Status changed from Open to Assigned
• Assignee set to hsbt (Hiroshi SHIBATA)

[hsbt (Hiroshi SHIBATA)]

@jeremyevans0 (Jeremy Evans) Thank you for your report. I confirmed this.

This issue was introduced RubyGems 4.0.5.

I will fix this at https://github.com/ruby/rubygems/pull/9404 and release RubyGems 4.0.9 with this fix at next week.

[hsbt (Hiroshi SHIBATA)]

• Status changed from Assigned to Closed

Fixed at https://github.com/ruby/ruby/commit/8ecf28f9384207590be73d5f2a95859cff9c526a