Feature #2975: Kernel.warn always writes despite $VERBOSE value
http://redmine.ruby-lang.org/issues/show/2975

Author: Dan Rathbun
Status: Open, Priority: Normal
Category: core

Kernel.warn always writes despite $VERBOSE value

The RDoc say:
http://www.ruby-doc.org/core/classes/Kernel.html#M005921
warn(msg) => nil
Display the given message (followed by a newline) on STDERR unless warnings are disabled (for example with the -W0 flag). 

(from Ruby.h, ver 1.8.6, line 562..564, Language="C" )
void rb_warning __((const char*, ...)); /* reports if `-w' specified */
void rb_sys_warning __((const char*, ...)); /* reports if `-w' specified */
void rb_warn __((const char*, ...)); /* reports always */

In ver 1.8.6, in practice Kernel.warn (and by inclusion,) anyobject's instance method warn, outputs no matter what the setting of $VERBOSE. It then appears to work as though it's calling rb_warn in the core, but the RDoc seems to say it should act like it's calling rb_warning in the core.

This has forced me to make my 'warn' calls work the way they should, by doing this:

# Send warning only if in Verbose mode
warn('My Informational Message') if $VERBOSE

# Send warning unless in Silent mode
warn('My Important Message') unless $VERBOSE.nil?

# Send warning no matter what Verbose mode
warn('My Critical Message that MUST be displayed!')

I'm tired of this workaround:
I think we need something like this overrride, where I define 3 methods,
warn, warn?, warn!
and in addition, I have them return a boolean result (the original warn just returned nil.)

#!ruby warn_ovr.rb
# Make Warnings work the way they should.
# by: Dan Rathbun - 16 MAR 2010 - Palm Bay, FL, USA
# TERMS: Public Domain, Take it, Use it, Abuse it!

module Kernel

  # alias the old warn method
  alias_method(:old_warn,:warn)

  # warn! will always send to $stderr
  # regardless of $VERBOSE setting
  def warn!(msg)
    unless msg.is_a?(String)
      raise(TypeError,'String argument expected.',caller(1))
    end
    $stderr.write(msg + "\n")
    return true # no IO error occured
  end

  # warn will now send to $stderr
  # ONLY if $VERBOSE is not Silent mode (nil)
  def warn(msg)
    unless msg.is_a?(String)
      raise(TypeError,'String argument expected.',caller(1))
    end
    unless $VERBOSE.nil?
      $stderr.write(msg + "\n")
      return true
    else
      return false
    end
  end

  # warn? will send to $stderr
  # ONLY if $VERBOSE is in Verbose mode (true)
  def warn?(msg)
    unless msg.is_a?(String)
      raise(TypeError,'String argument expected.',caller(1))
    end
    if $VERBOSE
      $stderr.write(msg + "\n")
      return true
    else
      # We return false if $VERBOSE is nil or false
      return false
    end
  end

end # Kernel

NOTE: The above override script does not override the Module method Kernel.warn, only the instance method. (I could have just run the script in the ObjectSpace without the Kernel wrapper, and added the methods to class Object. Their use either way is the same.)


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