Module: Warning
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(, category: nil, **kwargs)
if /some warning I want to ignore/.match?( )
# 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
-
.[](category) ⇒ Boolean
Returns the flag to show the warning messages for
category
. -
.[]=(category, flag) ⇒ flag
Sets the warning flags for
category
. -
.categories ⇒ Array
Returns a list of the supported category symbols.
Instance Method Summary
-
#warn(msg, category: nil) ⇒ nil
Writes warning message
msg
to $stderr.
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
etc.
-
:experimental
-
experimental features
:performance
-
performance hints
-
Shape variation limit
-
# File 'error.c', line 227
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.
# File 'error.c', line 242
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; }
.categories ⇒ Array
Returns a list of the supported category symbols.
# File 'error.c', line 262
static VALUE rb_warning_s_categories(VALUE mod) { st_index_t num = warning_categories.id2enum->num_entries; ID *ids = ALLOCA_N(ID, num); num = st_keys(warning_categories.id2enum, ids, num); VALUE ary = rb_ary_new_capa(num); for (st_index_t i = 0; i < num; ++i) { rb_ary_push(ary, ID2SYM(ids[i])); } return rb_ary_freeze(ary); }
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.
# File 'error.c', line 286
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; }