Enhancement for gem env

The following rewrite of show_environment suggests improvements of gem env output.

Feedback on further improvements or alternative angles appreciated.

Example output

RubyGems Environment:
  Version:
    - 4.0.20
  Platforms:
    - ruby
    - arm64-darwin-25
  Configuration:
    update_sources: true
    verbose: true
    backtrace: true
    bulk_threshold: 1000
    gem: --no-document
  Sources:
    - https://rubygems.org/
  Dependencies:
    Ruby version: 4.0.7 (2026-09-15 patchlevel 0) [arm64-darwin25]
    Ruby executable: /opt/homebrew/opt/ruby/bin/ruby
    Git executable: /usr/bin/git
  Directories:
    Global install: /opt/homebrew/lib/ruby/gems/4.0.0
    # Global config: /opt/homebrew/Cellar/ruby/4.0.7/etc
    Executable: /opt/homebrew/lib/ruby/gems/4.0.0/bin
    # User install: ~/.local/share/gem/ruby/4.0.0
    Spec cache: ~/.cache/gem/specs
    # Credentials: ~/.local/share/gem/credentials
  Gem path:
    - /opt/homebrew/lib/ruby/gems/4.0.0
    # - ~/.local/share/gem/ruby/4.0.0
    - /opt/homebrew/Cellar/ruby/4.0.7/lib/ruby/gems/4.0.0
  Shell path:
    - /opt/homebrew/bin
    - /opt/homebrew/sbin
    - /opt/homebrew/opt/ruby/bin
    - /usr/bin
    - /bin
    - /usr/sbin
    - /sbin
    - /opt/homebrew/lib/ruby/gems/4.0.0/bin

Code

  def exist(value)
    case value
    when %r{^/}
      File.stat(value)
    end
    ''
  rescue Errno::ENOENT
    '# '
  end

  def tree(items)
    items.flat_map do |group, items|
      items.compact.map do |item|
        item = [item].flatten
        line = exist(item.last) + (item.one? ? '- ' : '') + item.join(': ')
        line.prepend('    ').gsub(Dir.home, '~')
      end.prepend(format('  %s:', group))
    end
  end

  def show_environment # :nodoc:
    config = {}
    Gem.configuration.each do |name, value|
      config[name] = name == 'gemcutter_key' ? value.gsub(/./, '*') : value
    end
    {
      'Version' => [Gem::VERSION],
      'Platforms' => Gem.platforms.map(&:to_s),
      'Configuration' => config,
      'Sources' => Gem.sources.to_a,
      'Dependencies' => {
        'Ruby version' => "#{RUBY_VERSION} (#{RUBY_RELEASE_DATE} patchlevel #{RUBY_PATCHLEVEL}) [#{RUBY_PLATFORM}]",
        'Ruby executable' => Gem.ruby,
        'Git executable' => git_path
      },
      'Directories' => {
        'Global install' => Gem.dir,
        'Global config' => Gem::ConfigFile::SYSTEM_CONFIG_PATH,
        'Executable' => Gem.bindir,
        'User install' => Gem.user_dir,
        'Prefix' => Gem.prefix,
        'Spec cache' => Gem.spec_cache_dir,
        'Credentials' => Gem.configuration.credentials_path
      },
      'Gem path' => ([Gem.dir] + Gem.path).uniq,
      'Shell path' => ENV['PATH'].split(File::PATH_SEPARATOR)
    }.then { tree(it).prepend('RubyGems Environment:').join("\n") }
  end

Start by reading the proposed show_environment implementation and running gem env to compare its current output with the YAML example. Review how the listed configuration, directory, gem path, and shell path values are assembled. Done means agreeing on the output format and implementing the proposed presence checks, home-directory redaction, and centralized formatting.