class Gem::Commands::BuildCommand

def arguments # :nodoc:
  "GEMSPEC_FILE  gemspec file name to build a gem for"
end

def build_gem
  gemspec = resolve_gem_name
  if gemspec
    build_package(gemspec)
  else
    alert_error error_message
    terminate_interaction(1)
  end
end

def build_package(gemspec)
  spec = Gem::Specification.load(gemspec)
  if spec
    Gem::Package.build(
      spec,
      options[:force],
      options[:strict],
      options[:output]
    )
  else
    alert_error "Error loading gemspec. Aborting."
    terminate_interaction 1
  end
end

def description # :nodoc:
  <<-EOF
e build command allows you to create a gem from a ruby gemspec.
e best way to build a gem is to use a Rakefile and the Gem::PackageTask
ich ships with RubyGems.
e gemspec can either be created by hand or extracted from an existing gem
th gem spec:
$ gem unpack my_gem-1.0.gem
Unpacked gem: '.../my_gem-1.0'
$ gem spec my_gem-1.0.gem --ruby > my_gem-1.0/my_gem-1.0.gemspec
$ cd my_gem-1.0
[edit gem contents]
$ gem build my_gem-1.0.gemspec
ms can be saved to a specified filename with the output option:
$ gem build my_gem-1.0.gemspec --output=release.gem
  EOF
end

def error_message
  if gem_name
    "Couldn't find a gemspec file matching '#{gem_name}' in #{Dir.pwd}"
  else
    "Couldn't find a gemspec file in #{Dir.pwd}"
  end
end

def execute
  if build_path = options[:build_path]
    Dir.chdir(build_path) { build_gem }
    return
  end
  build_gem
end

def gem_name
  get_one_optional_argument
end

def initialize
  super "build", "Build a gem from a gemspec"
  add_platform_option
  add_option "--force", "skip validation of the spec" do |_value, options|
    options[:force] = true
  end
  add_option "--strict", "consider warnings as errors when validating the spec" do |_value, options|
    options[:strict] = true
  end
  add_option "-o", "--output FILE", "output gem with the given filename" do |value, options|
    options[:output] = value
  end
  add_option "-C PATH", "Run as if gem build was started in <PATH> instead of the current working directory." do |value, options|
    options[:build_path] = value
  end
  deprecate_option "-C",
                   version: "4.0",
                   extra_msg: "-C is a global flag now. Use `gem -C PATH build GEMSPEC_FILE [options]` instead"
end

def resolve_gem_name
  return find_gemspec unless gem_name
  if File.exist?(gem_name)
    gem_name
  else
    find_gemspec("#{gem_name}.gemspec") || find_gemspec(gem_name)
  end
end

def usage # :nodoc:
  "#{program_name} GEMSPEC_FILE"
end