class Tilt::Template

def local_extraction(local_keys)
  assignments = local_keys.map do |k|
    if k.to_s =~ /\A[a-z_][a-zA-Z_0-9]*\z/
      "#{k} = locals[#{k.inspect}]"
    else
      raise "invalid locals key: #{k.inspect} (keys must be variable names)"
    end
  end
  s = "locals = locals[:locals]"
  if assignments.delete(s)
    # If there is a locals key itself named `locals`, delete it from the ordered keys so we can
    # assign it last. This is important because the assignment of all other locals depends on the
    # `locals` local variable still matching the `locals` method argument given to the method
    # created in `#compile_template_method`.
    assignments << s
  end
  assignments.join("\n")
end