Make Warning.warn accept only category keyword

In general accepting arbitrary keywords is a bad idea unless you are
delegating keywords or acting on arbitrary keywords.  In this case,
the category keyword is ignored, and it's less error prone to not
ignore all keywords.

2 files changed, 9 insertions, 4 deletions

diff --git a/error.c b/error.c
index 9f8cdf8fe6..e064eef4bc 100644
--- a/error.c
+++ b/error.c
@@ -72,6 +72,7 @@ static VALUE rb_mWarning;
 static VALUE rb_cWarningBuffer;
 
 static ID id_warn;
+static ID id_category;
 
 extern const char ruby_description[];
 
@@ -231,11 +232,11 @@ rb_warning_s_aset(VALUE mod, VALUE category, VALUE flag)
 
 /*
  * call-seq:
- *    warn(msg, **kw)  -> nil
+ *    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.
+ * the warning, but is ignored by default.
  */
 
 static VALUE
@@ -243,8 +244,11 @@ rb_warning_s_warn(int argc, VALUE *argv, VALUE mod)
 {
     VALUE str;
     VALUE opt;
+    VALUE category;
 
     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);
     rb_write_error_str(str);
@@ -2749,6 +2753,7 @@ Init_Exception(void)
     id_errno = rb_intern_const("errno");
     id_i_path = rb_intern_const("@path");
     id_warn = rb_intern_const("warn");
+    id_category = rb_intern_const("category");
     id_top = rb_intern_const("top");
     id_bottom = rb_intern_const("bottom");
     id_iseq = rb_make_internal_id();
diff --git a/test/ruby/test_exception.rb b/test/ruby/test_exception.rb
index 120b041830..0333fd52ea 100644
--- a/test/ruby/test_exception.rb
+++ b/test/ruby/test_exception.rb
@@ -925,8 +925,8 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
       remove_method :warn
 
       if category
-        define_method(:warn) do |str, **kw|
-          warning << [str, kw[:category]]
+        define_method(:warn) do |str, category: nil|
+          warning << [str, category]
         end
       else
         define_method(:warn) do |str|