Gem::Commands::LockCommand#spec_path

# File tmp/rubies/ruby-4.1.0-preview1/lib/rubygems/commands/lock_command.rb, line 102
def spec_path(gem_full_name)
  gemspecs = Gem::SpecificationRecord.dirs_from(Gem.path).map do |spec_dir|
    File.join spec_dir, "#{gem_full_name}.gemspec"
  end

  gemspecs.find {|path| File.exist? path }
end