Fix usage of rb_struct_initialize() to pass an Array of members values and not a Hash

* rb_struct_initialize() does not accept a Hash, and it's very brittle
  to pass `[{...}]` and to rely on that C function using rb_keyword_given_p().
  It basically worked accidentally, by having **members in the caller of the caller.
  Such logic when Struct#initialize is defined in Ruby (as in TruffleRuby) is basically impossible to implement,
  because it's incorrectly treating positional arguments as keyword arguments.
* rb_struct_initialize() is used in CRuby to set members of Data instances in marshal.c (there is no rb_data_initialize() yet).
  There, the code passes an Array of members values for Data (and for Struct which are not `keyword_init: true`):
  https://github.com/ruby/ruby/blob/48c7f349f68846e10d60ae77ad299a38ee014479/marshal.c#L2150-L2176
  So we should do the same in psych.
* Rename to init_data since it's only used for Data.
* See #692 (comment).

Author: eregon

.github/workflows/test.yml

@@ -26,7 +26,7 @@ jobs:
         ruby: ${{ fromJson(needs.ruby-versions.outputs.versions) }}
         os: [ ubuntu-latest, macos-latest, windows-latest ]
         include:
-          # jruby is broken with "undefined method 'init_struct'"
+          # jruby is broken with "undefined method 'init_data'"
           # https://github.com/ruby/psych/actions/runs/15434465445/job/43438083198?pr=734
           - { os: windows-latest, ruby: jruby-head }
           - { os: macos-latest, ruby: jruby-head }

ext/psych/psych_to_ruby.c

@@ -24,12 +24,9 @@ static VALUE path2class(VALUE self, VALUE path)
     return rb_path_to_class(path);
 }
 
-static VALUE init_struct(VALUE self, VALUE data, VALUE attrs)
+static VALUE init_data(VALUE self, VALUE data, VALUE values)
 {
-    VALUE args = rb_ary_new2(1);
-    rb_ary_push(args, attrs);
-    rb_struct_initialize(data, args);
-
+    rb_struct_initialize(data, values);
     return data;
 }
 
@@ -42,7 +39,7 @@ void Init_psych_to_ruby(void)
     VALUE visitor   = rb_define_class_under(visitors, "Visitor", rb_cObject);
     cPsychVisitorsToRuby = rb_define_class_under(visitors, "ToRuby", visitor);
 
-    rb_define_private_method(cPsychVisitorsToRuby, "init_struct", init_struct, 2);
+    rb_define_private_method(cPsychVisitorsToRuby, "init_data", init_data, 2);
     rb_define_private_method(cPsychVisitorsToRuby, "build_exception", build_exception, 2);
     rb_define_private_method(class_loader, "path2class", path2class, 1);
 }

lib/psych/visitors/to_ruby.rb

@@ -219,7 +219,8 @@ def visit_Psych_Nodes_Mapping o
             revive_data_members(members, o)
           end
           data ||= allocate_anon_data(o, members)
-          init_struct(data, **members)
+          values = data.members.map { |m| members[m] }
+          init_data(data, values)
           data.freeze
           data