module StructuredWarnings::Kernel

This method provides a raise-like interface. It extends the default warn in ::Kernel to allow the use of structured warnings.

Internally it uses the StructuredWarnings::warner to format a message based on the given warning class, the message and a stack frame. The return value is passed to super, which is likely the implementation in ::Kernel. That way, it is less likely, that structured_warnings interferes with other extensions.

It the warner return nil or an empty string the underlying warn will not be called. That way, warnings may be transferred to other devices without the need to redefine ::Kernel#warn.

Just like the original version, this method does not take command line switches or verbosity levels into account. In order to deactivate all warnings use Warning.disable.

warn "This is an old-style warning" # This will emit a StandardWarning

class Foo
  def bar
    warn DeprecationWarning, "Never use bar again, use beer"
  end
  def beer
    "Ahhh"
  end
end

warn Warning.new("The least specific warning you can get")

# File lib/structured_warnings/kernel.rb, line 41
def warn(*args)
  first = args.shift
  if first.is_a? Class and first <= Warning
    warning = first
    message = args.shift

  elsif first.is_a? Warning
    warning = first.class
    message = first.message

  else
    warning = StandardWarning
    message = first.to_s
  end

  # If args is not empty, user passed an incompatible set of arguments.
  # Maybe somebody else is overriding warn as well and knows, what to do.
  # Better do nothing in this case. See #5
  return super unless args.empty?

  if warning.active?
    output = StructuredWarnings.warner.format(warning, message, caller(1))
    super(output) unless output.nil? or output.to_s.empty?
  end
end