Classes made from Struct should have default new singleton method.

[Bug #16465] [Bug #16801]
[Fix GH-2795] [Fix GH-2944] [Fix GH-3045] [Fix GH-3093]

Note: Backporting shouldn't modify object.h and instead can use
struct_new_kw which is basically a duplicate implementation of
rb_class_new_instance_pass_kw

Co-authored-by: Yusuke Endoh <mame@ruby-lang.org>
Co-authored-by: John Hawthorn <john@hawthorn.email>
Co-authored-by: Adam Hess <HParker@github.com>
Co-authored-by: Jose Cortinas <jacortinas@gmail.com>
Co-authored-by: Jean Boussier <jean.boussier@gmail.com>

include/ruby/3/intern/object.h

@@ -30,6 +30,7 @@ RUBY3_SYMBOL_EXPORT_BEGIN()
     ((obj) != (orig) && (rb_obj_init_copy((obj), (orig)), 1))
 #define OBJ_INIT_COPY(obj, orig) RB_OBJ_INIT_COPY(obj, orig)
 
+VALUE rb_class_new_instance_pass_kw(int, const VALUE *, VALUE);
 VALUE rb_class_new_instance(int, const VALUE*, VALUE);
 VALUE rb_class_new_instance_kw(int, const VALUE*, VALUE, int);
 

object.c

@@ -2203,8 +2203,8 @@ rb_class_allocate_instance(VALUE klass)
  *
  */
 
-static VALUE
-rb_class_s_new(int argc, const VALUE *argv, VALUE klass)
+VALUE
+rb_class_new_instance_pass_kw(int argc, const VALUE *argv, VALUE klass)
 {
     VALUE obj;
 
@@ -4726,7 +4726,7 @@ InitVM_Object(void)
     rb_define_method(rb_cModule, "singleton_class?", rb_mod_singleton_p, 0);
 
     rb_define_method(rb_cClass, "allocate", rb_class_alloc_m, 0);
-    rb_define_method(rb_cClass, "new", rb_class_s_new, -1);
+    rb_define_method(rb_cClass, "new", rb_class_new_instance_pass_kw, -1);
     rb_define_method(rb_cClass, "initialize", rb_class_initialize, -1);
     rb_define_method(rb_cClass, "superclass", rb_class_superclass, 0);
     rb_define_alloc_func(rb_cClass, rb_class_s_alloc);

struct.c

@@ -317,24 +317,15 @@ rb_struct_s_inspect(VALUE klass)
 }
 
 static VALUE
-struct_new_kw(int argc, const VALUE *argv, VALUE klass)
-{
-    return rb_class_new_instance_kw(argc, argv, klass, RB_PASS_CALLED_KEYWORDS);
-}
-
-static VALUE
-setup_struct(VALUE nstr, VALUE members, int keyword_init)
+setup_struct(VALUE nstr, VALUE members)
 {
     long i, len;
-    VALUE (*new_func)(int, const VALUE *, VALUE) = rb_class_new_instance;
-
-    if (keyword_init) new_func = struct_new_kw;
 
     members = struct_set_members(nstr, members);
 
     rb_define_alloc_func(nstr, struct_alloc);
-    rb_define_singleton_method(nstr, "new", new_func, -1);
-    rb_define_singleton_method(nstr, "[]", new_func, -1);
+    rb_define_singleton_method(nstr, "new", rb_class_new_instance_pass_kw, -1);
+    rb_define_singleton_method(nstr, "[]", rb_class_new_instance_pass_kw, -1);
     rb_define_singleton_method(nstr, "members", rb_struct_s_members_m, 0);
     rb_define_singleton_method(nstr, "inspect", rb_struct_s_inspect, 0);
     len = RARRAY_LEN(members);
@@ -449,7 +440,7 @@ rb_struct_define(const char *name, ...)
 
     if (!name) st = anonymous_struct(rb_cStruct);
     else st = new_struct(rb_str_new2(name), rb_cStruct);
-    return setup_struct(st, ary, 0);
+    return setup_struct(st, ary);
 }
 
 VALUE
@@ -462,7 +453,7 @@ rb_struct_define_under(VALUE outer, const char *name, ...)
     ary = struct_make_members_list(ar);
     va_end(ar);
 
-    return setup_struct(rb_define_class_under(outer, name, rb_cStruct), ary, 0);
+    return setup_struct(rb_define_class_under(outer, name, rb_cStruct), ary);
 }
 
 /*
@@ -581,7 +572,7 @@ rb_struct_s_def(int argc, VALUE *argv, VALUE klass)
     else {
 	st = new_struct(name, klass);
     }
-    setup_struct(st, rest, (int)keyword_init);
+    setup_struct(st, rest);
     rb_ivar_set(st, id_keyword_init, keyword_init);
     if (rb_block_given_p()) {
         rb_mod_module_eval(0, 0, st);

test/ruby/test_struct.rb

@@ -118,10 +118,9 @@ module TestStruct
     assert_equal "#{@Struct}::KeywordInitFalse", @Struct::KeywordInitFalse.inspect
     assert_equal "#{@Struct}::KeywordInitTrue(keyword_init: true)", @Struct::KeywordInitTrue.inspect
     # eval is needed to prevent the warning duplication filter
-    k = eval("Class.new(@Struct::KeywordInitFalse) {def initialize(**) end}")
-    assert_raise(ArgumentError) { k.new(a: 1, b: 2) }
-    k = Class.new(@Struct::KeywordInitTrue) {def initialize(**) end}
-    assert_warn('') {k.new(a: 1, b: 2)}
+    k = Class.new(@Struct::KeywordInitTrue) {def initialize(b, options); super(a: options, b: b); end}
+    o = assert_warn('') { k.new(42, {foo: 1, bar: 2}) }
+    assert_equal(1, o.a[:foo])
 
     @Struct.instance_eval do
       remove_const(:KeywordInitTrue)
@@ -150,6 +149,17 @@ module TestStruct
     assert_equal 3, klass.new(1,2).total
   end
 
+  def test_initialize_with_kw
+    klass = @Struct.new(:foo, :options) do
+      def initialize(foo, **options)
+        super(foo, options)
+      end
+    end
+    assert_equal({}, klass.new(42, **Hash.new).options)
+    x = assert_warn('') { klass.new(1, bar: 2) }
+    assert_equal 2, x.options[:bar]
+  end
+
   def test_each
     klass = @Struct.new(:a, :b)
     o = klass.new(1, 2)