From 1ad366134ded1667745dd9fa70919051869f8d6c Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Thu, 22 Feb 2024 22:25:12 +0900
Subject: [PATCH] [Feature #20293] Add `Warning.categories`

---
 error.c                       | 21 +++++++++++++++++++++
 test/ruby/test_rubyoptions.rb |  3 ++-
 tool/lib/envutil.rb           |  4 +++-
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/error.c b/error.c
index 5d1cbcc8da..9c5b70d1d6 100644
--- a/error.c
+++ b/error.c
@@ -252,6 +252,26 @@ rb_warning_s_aset(VALUE mod, VALUE category, VALUE flag)
     return flag;
 }
 
+/*
+ * call-seq:
+ *   categories  -> array
+ *
+ * Returns a list of the supported category symbols.
+ */
+
+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);
+}
+
 /*
  * call-seq:
  *    warn(msg, category: nil)  -> nil
@@ -3413,6 +3433,7 @@ Init_Exception(void)
     rb_mWarning = rb_define_module("Warning");
     rb_define_singleton_method(rb_mWarning, "[]", rb_warning_s_aref, 1);
     rb_define_singleton_method(rb_mWarning, "[]=", rb_warning_s_aset, 2);
+    rb_define_singleton_method(rb_mWarning, "categories", rb_warning_s_categories, 0);
     rb_define_method(rb_mWarning, "warn", rb_warning_s_warn, -1);
     rb_extend_object(rb_mWarning, rb_mWarning);
 
diff --git a/test/ruby/test_rubyoptions.rb b/test/ruby/test_rubyoptions.rb
index d5626a1a94..29810d5dd7 100644
--- a/test/ruby/test_rubyoptions.rb
+++ b/test/ruby/test_rubyoptions.rb
@@ -112,7 +112,8 @@ class TestRubyOptions < Test::Unit::TestCase
     assert_in_out_err(%w(-We) + ['p $-W'], "", %w(2), [])
     assert_in_out_err(%w(-w -W0 -e) + ['p $-W'], "", %w(0), [])
 
-    categories = {"deprecated"=>1, "experimental"=>0, "performance"=>2}
+    categories = {deprecated: 1, experimental: 0, performance: 2}
+    assert_equal categories.keys.sort, Warning.categories.sort
 
     categories.each do |category, level|
       assert_in_out_err(["-W:#{category}", "-e", "p Warning[:#{category}]"], "", %w(true), [])
diff --git a/tool/lib/envutil.rb b/tool/lib/envutil.rb
index a2ddf74052..642965047f 100644
--- a/tool/lib/envutil.rb
+++ b/tool/lib/envutil.rb
@@ -53,7 +53,9 @@ module EnvUtil
       @original_external_encoding = Encoding.default_external
       @original_verbose = $VERBOSE
       @original_warning =
-        if defined?(Warning.[]) # 2.7+
+        if defined?(Warning.categories)
+          Warning.categories.to_h {|i| [i, Warning[i]]}
+        elsif defined?(Warning.[]) # 2.7+
           %i[deprecated experimental performance].to_h do |i|
             [i, begin Warning[i]; rescue ArgumentError; end]
           end.compact