The Warning module contains a single method named warn, and the module extends itself, making Warning.warn available. Warning.warn is called for all warnings issued by Ruby. By default, warnings are printed to $stderr.
Changing the behavior of Warning.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 Warning.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/.matches?(message) # ignore else super end end end Warning.extend MyWarningFilter
You should never redefine Warning#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 Warning.warn.
static VALUE
rb_warning_s_aref(VALUE mod, VALUE category)
{
rb_warning_category_t cat = rb_warning_category_from_name(category);
if (rb_warning_category_enabled_p(cat))
return Qtrue;
return Qfalse;
}
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
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;
}
Sets the warning flags for category. See Warning.[] for the categories.
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;
}
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.