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Module: Warning

Relationships & Source Files
Namespace Children
Classes:
buffer
Defined in: error.c

Overview

The Warning module contains a single method named #warn, and the module extends itself, making #warn available. #warn is called for all warnings issued by Ruby. By default, warnings are printed to $stderr.

Changing the behavior of #warn is useful to customize how warnings are handled by Ruby, for instance by filtering some warnings, and/or outputting warnings somewhere other than $stderr.

If you want to change the behavior of #warn you should use Warning.extend(MyNewModuleWithWarnMethod) and you can use super to get the default behavior of printing the warning to $stderr.

Example:

module MyWarningFilter
  def warn(message, category: nil, **kwargs)
    if /some warning I want to ignore/.match?(message)
      # ignore
    else
      super
    end
  end
end
Warning.extend MyWarningFilter

You should never redefine #warn (the instance method), as that will then no longer provide a way to use the default behavior.

The warning gem provides convenient ways to customize #warn.

Class Method Summary

Instance Method Summary

Class Method Details

.[](category) ⇒ Boolean

Returns the flag to show the warning messages for category. Supported categories are:

:deprecated

deprecation warnings

  • assignment of non-nil value to $, and $;

  • keyword arguments

  • proc/lambda without block

etc.

:experimental

experimental features

  • Pattern matching

[ GitHub ] 

  


# File 'error.c', line 217



static VALUE
rb_warning_s_aref(VALUE mod, VALUE category)
{
    rb_warning_category_t cat = rb_warning_category_from_name(category);
    return RBOOL(rb_warning_category_enabled_p(cat));
}


  








  

    .[]=(category, flag)  ⇒ flag   



  

    

Sets the warning flags for category. See .[] for the categories.


  



  [ GitHub ]


  

  


# File 'error.c', line 232



static VALUE
rb_warning_s_aset(VALUE mod, VALUE category, VALUE flag)
{
    unsigned int mask = rb_warning_category_mask(category);
    unsigned int disabled = warning_disabled_categories;
    if (!RTEST(flag))
        disabled |= mask;
    else
        disabled &= ~mask;
    warning_disabled_categories = disabled;
    return flag;
}


  







Instance Method Details



  

    #warn(msg, category: nil)  ⇒ nil   



  

    

Writes warning message msg to $stderr. This method is called by Ruby for all emitted warnings. A category may be included with the warning.



See the documentation of the Warning module for how to customize this.


  



  [ GitHub ]


  

  


# File 'error.c', line 256



static VALUE
rb_warning_s_warn(int argc, VALUE *argv, VALUE mod)
{
    VALUE str;
    VALUE opt;
    VALUE category = Qnil;

    rb_scan_args(argc, argv, "1:", &str, &opt);
    if (!NIL_P(opt)) rb_get_kwargs(opt, &id_category, 0, 1, &category);

    Check_Type(str, T_STRING);
    rb_must_asciicompat(str);
    if (!NIL_P(category)) {
        rb_warning_category_t cat = rb_warning_category_from_name(category);
        if (!rb_warning_category_enabled_p(cat)) return Qnil;
    }
    rb_write_error_str(str);
    return Qnil;
}