From 8538c79f3f3b729e4e9c388cecdb02bbd5c562eb Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Fri, 20 Jun 2025 13:53:26 +0900
Subject: [PATCH] mruby-set: refactor Set#merge

The code is written by Atlassian Rovodev.
---
 mrbgems/mruby-set/mrblib/set.rb | 18 +++++++++---
 mrbgems/mruby-set/src/set.c     | 50 ++++++++++++++-------------------
 2 files changed, 35 insertions(+), 33 deletions(-)

diff --git a/mrbgems/mruby-set/mrblib/set.rb b/mrbgems/mruby-set/mrblib/set.rb
index 16e35428b..6509af374 100644
--- a/mrbgems/mruby-set/mrblib/set.rb
+++ b/mrbgems/mruby-set/mrblib/set.rb
@@ -14,10 +14,20 @@ class Set
     self
   end
 
-  # Helper method for merge with enumerable
-  def __merge_enum(enum)
-    __do_with_enum(enum) { |o| add(o) }
-    self
+  # Merges the elements of the given enumerable object to the set and returns
+  # self.
+  #
+  # @param [Enumerable] enum The enumerable object to merge elements from
+  # @return [Set] self
+  def merge(enum)
+    if enum.is_a?(Set)
+      # Fast path: Call C-implemented function for Set-to-Set merge
+      __set_merge(enum)
+    else
+      # General path: Add each element from the enumerable
+      __do_with_enum(enum) { |o| add(o) }
+      self
+    end
   end
 
   # Deletes every element that appears in the given enumerable object and
diff --git a/mrbgems/mruby-set/src/set.c b/mrbgems/mruby-set/src/set.c
index ad08139dd..cbedbe3a7 100644
--- a/mrbgems/mruby-set/src/set.c
+++ b/mrbgems/mruby-set/src/set.c
@@ -322,47 +322,39 @@ set_replace(mrb_state *mrb, mrb_value self)
   mrb_value enum_obj;
 
   mrb_get_args(mrb, "o", &enum_obj);
-  mrb_funcall_id(mrb, self, MRB_SYM(clear), 0);
+  set_clear(mrb, self);
   return mrb_funcall_id(mrb, self, MRB_SYM(merge), 1, enum_obj);
 }
 
 /*
- * call-seq:
- *   set.merge(enum) -> self
- *
- * Merges the elements of the given enumerable object to the set and returns
- * self.
+ * Core implementation of Set-to-Set merge (mutating version)
+ * This is an internal method that will be called from Ruby
  */
 static mrb_value
-set_merge(mrb_state *mrb, mrb_value self)
+set_core_merge(mrb_state *mrb, mrb_value self)
 {
-  mrb_value enum_obj;
-  khash_t(set) *kh;
+  mrb_value other;
+  khash_t(set) *self_kh, *other_kh;
 
-  mrb_get_args(mrb, "o", &enum_obj);
-  kh = set_get_khash(mrb, self);
-  if (!kh) {
+  mrb_get_args(mrb, "o", &other);
+
+  self_kh = set_get_khash(mrb, self);
+  if (!self_kh) {
     mrb_raise(mrb, E_RUNTIME_ERROR, "uninitialized Set");
   }
 
-  if (mrb_obj_class(mrb, enum_obj) == mrb_obj_class(mrb, self)) {
-    /* Optimized path for Set objects - direct khash merge */
-    khash_t(set) *other_kh = set_get_khash(mrb, enum_obj);
-    if (other_kh) {
-      khiter_t k;
-      int ai = mrb_gc_arena_save(mrb);
-      for (k = kh_begin(other_kh); k != kh_end(other_kh); k++) {
-        if (kh_exist(other_kh, k)) {
-          kh_put(set, mrb, kh, kh_key(other_kh, k));
-          mrb_gc_arena_restore(mrb, ai);
-        }
-      }
+  other_kh = set_get_khash(mrb, other);
+  if (!other_kh) return self;
+
+  /* Add all elements from other set */
+  khiter_t k;
+  int ai = mrb_gc_arena_save(mrb);
+  for (k = kh_begin(other_kh); k != kh_end(other_kh); k++) {
+    if (kh_exist(other_kh, k)) {
+      kh_put(set, mrb, self_kh, kh_key(other_kh, k));
+      mrb_gc_arena_restore(mrb, ai);
     }
   }
-  else {
-    /* General enumerable path - delegate to Ruby */
-    return mrb_funcall_with_block(mrb, self, MRB_SYM(__merge_enum), 1, &enum_obj, mrb_nil_value());
-  }
 
   return self;
 }
@@ -953,7 +945,7 @@ mrb_mruby_set_gem_init(mrb_state *mrb)
   mrb_define_method(mrb, set, "delete?", set_delete_p, MRB_ARGS_REQ(1));
 
   mrb_define_method(mrb, set, "replace", set_replace, MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, set, "merge", set_merge, MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, set, "__set_merge", set_core_merge, MRB_ARGS_REQ(1));
   mrb_define_method(mrb, set, "__set_subtract", set_core_subtract, MRB_ARGS_REQ(1));
 
   mrb_define_method(mrb, set, "__set_union", set_core_union, MRB_ARGS_REQ(1));