TIL: Ruby Warnings

Ruby has a built in warning mechanism in Kernel#warn.

class Foo
  def deprecated_method
    warn('The `deprecated_method` is deprecated, use `not_deprecated` instead.', uplevel: 1)
    not_deprecated
  end
  
  def not_deprecated
  end
end

The uplevel: 1 gives information about the current frame of execution (the filename and line number). Super useful for deprecating methods.

Note though, all warning can be supressed if warning have been disabled for the runtime, e.g. through the -W0 flag.