module Jekyll::External

def blessed_gems


Usually contain subcommands.
Gems that, if installed, should be loaded.
def blessed_gems
  %w(
    jekyll-docs
    jekyll-import
  )
end

def require_if_present(names)


names - a string gem name or array of gem names

Require a gem or file if it's present, otherwise silently fail.
def require_if_present(names)
  Array(names).each do |name|
    begin
      require name
    rescue LoadError
      Jekyll.logger.debug "Couldn't load #{name}. Skipping."
      yield(name) if block_given?
      false
    end
  end
end

def require_with_graceful_fail(names)


names - a string gem name or array of gem names

normal LoadError.
message that explains everything and is much more helpful than the
Require a gem or gems. If it's not present, show a very nice error
def require_with_graceful_fail(names)
  Array(names).each do |name|
    begin
      Jekyll.logger.debug "Requiring:", name.to_s
      require name
    rescue LoadError => e
      Jekyll.logger.error "Dependency Error:", <<-MSG
 It looks like you don't have #{name} or one of its dependencies installed.
er to use Jekyll as currently configured, you'll need to install this gem.
ll error message from Ruby is: '#{e.message}'
 run into trouble, you can find helpful resources at http://jekyllrb.com/help/!
      MSG
      raise Jekyll::Errors::MissingDependencyException, name
    end
  end
end