From 594410467bc64b75c730dec01693270c735d2db1 Mon Sep 17 00:00:00 2001
From: Dmitry Panov <dop@itoolabs.com>
Date: Tue, 24 Oct 2023 19:09:52 +0100
Subject: [PATCH] Correctly detect circular references in JSON.stringify for
 wrapped Go objects. Fixes #543.

---
 builtin_json.go      |  2 +-
 builtin_json_test.go | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/builtin_json.go b/builtin_json.go
index 9b69d902..e99771cf 100644
--- a/builtin_json.go
+++ b/builtin_json.go
@@ -359,7 +359,7 @@ func (ctx *_builtinJSON_stringifyContext) str(key Value, holder *Object) bool {
 		ctx.buf.WriteString("null")
 	case *Object:
 		for _, object := range ctx.stack {
-			if value1 == object {
+			if value1.SameAs(object) {
 				ctx.r.typeErrorResult(true, "Converting circular structure to JSON")
 			}
 		}
diff --git a/builtin_json_test.go b/builtin_json_test.go
index 3dfeba5b..a71c54e4 100644
--- a/builtin_json_test.go
+++ b/builtin_json_test.go
@@ -48,6 +48,23 @@ func TestJSONMarshalObjectCircular(t *testing.T) {
 	}
 }
 
+func TestJSONStringifyCircularWrappedGo(t *testing.T) {
+	type CircularType struct {
+		Self *CircularType
+	}
+	vm := New()
+	v := CircularType{}
+	v.Self = &v
+	vm.Set("v", &v)
+	_, err := vm.RunString("JSON.stringify(v)")
+	if err == nil {
+		t.Fatal("Expected error")
+	}
+	if !strings.HasPrefix(err.Error(), "TypeError: Converting circular structure to JSON") {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+}
+
 func TestJSONParseReviver(t *testing.T) {
 	// example from
 	// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse