class Gem::Commands::UnpackCommand

# File lib/rubygems/commands/unpack_command.rb, line 20
def initialize
  require 'fileutils'

  super 'unpack', 'Unpack an installed gem to the current directory',
        :version => Gem::Requirement.default,
        :target  => Dir.pwd

  add_option('--target=DIR',
             'target directory for unpacking') do |value, options|
    options[:target] = value
  end

  add_option('--spec', 'unpack the gem specification') do |value, options|
    options[:spec] = true
  end

  add_security_option
  add_version_option
end

# File lib/rubygems/commands/unpack_command.rb, line 48
  def description
    <<-EOF
The unpack command allows you to examine the contents of a gem or modify
them to help diagnose a bug.

You can add the contents of the unpacked gem to the load path using the
RUBYLIB environment variable or -I:

  $ gem unpack my_gem
  Unpacked gem: '.../my_gem-1.0'
  [edit my_gem-1.0/lib/my_gem.rb]
  $ ruby -Imy_gem-1.0/lib -S other_program

You can repackage an unpacked gem using the build command.  See the build
command help for an example.
    EOF
  end

# File lib/rubygems/commands/unpack_command.rb, line 75
def execute
  security_policy = options[:security_policy]

  get_all_gem_names.each do |name|
    dependency = Gem::Dependency.new name, options[:version]
    path = get_path dependency

    unless path
      alert_error "Gem '#{name}' not installed nor fetchable."
      next
    end

    if @options[:spec]
      spec, metadata = get_metadata path, security_policy

      if metadata.nil?
        alert_error "--spec is unsupported on '#{name}' (old format gem)"
        next
      end

      spec_file = File.basename spec.spec_file

      FileUtils.mkdir_p @options[:target] if @options[:target]

      destination = begin
        if @options[:target]
          File.join @options[:target], spec_file
        else
          spec_file
        end
      end

      File.open destination, 'w' do |io|
        io.write metadata
      end
    else
      basename = File.basename path, '.gem'
      target_dir = File.expand_path basename, options[:target]

      package = Gem::Package.new path, security_policy
      package.extract_files target_dir

      say "Unpacked gem: '#{target_dir}'"
    end
  end
end

# File lib/rubygems/commands/unpack_command.rb, line 129
def find_in_cache(filename)
  Gem.path.each do |path|
    this_path = File.join(path, "cache", filename)
    return this_path if File.exist? this_path
  end

  return nil
end

# File lib/rubygems/commands/unpack_command.rb, line 183
def get_metadata(path, security_policy = nil)
  format = Gem::Package.new path, security_policy
  spec = format.spec

  metadata = nil

  File.open path, Gem.binary_mode do |io|
    tar = Gem::Package::TarReader.new io
    tar.each_entry do |entry|
      case entry.full_name
      when 'metadata' then
        metadata = entry.read
      when 'metadata.gz' then
        metadata = Gem::Util.gunzip entry.read
      end
    end
  end

  return spec, metadata
end

# File lib/rubygems/commands/unpack_command.rb, line 155
def get_path(dependency)
  return dependency.name if dependency.name =~ /\.gem$/i

  specs = dependency.matching_specs

  selected = specs.max_by { |s| s.version }

  return Gem::RemoteFetcher.fetcher.download_to_cache(dependency) unless
    selected

  return unless dependency.name =~ /^#{selected.name}$/i

  # We expect to find (basename).gem in the 'cache' directory.  Furthermore,
  # the name match must be exact (ignoring case).

  path = find_in_cache File.basename selected.cache_file

  return Gem::RemoteFetcher.fetcher.download_to_cache(dependency) unless path

  path
end