From e32fc5b82711ace47849baefcb0c836b48404653 Mon Sep 17 00:00:00 2001
From: Tom Duncalf <tom.duncalf@mongodb.com>
Date: Mon, 5 Sep 2022 15:17:13 +0100
Subject: [PATCH] Refactor to use class static which is reset when env is
 destroyed

---
 src/jsi/jsi_class.hpp | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/jsi/jsi_class.hpp b/src/jsi/jsi_class.hpp
index 851cdba2cbd..5bf6f46411b 100644
--- a/src/jsi/jsi_class.hpp
+++ b/src/jsi/jsi_class.hpp
@@ -240,6 +240,10 @@ class ObjectWrap {
     // Also, may need to suppress destruction.
     inline static std::optional<JsiFunc> s_ctor;
 
+    // Cache the JSI String instance representing the field name of the internal
+    // C++ object for the lifetime of the current env, as this is a hot path
+    inline static std::optional<fbjsi::String> s_js_internal_field_name;
+
     /**
      * @brief callback for invalid access to index setters
      * Throws an error when a users attemps to write to an index on a type that
@@ -310,9 +314,10 @@ class ObjectWrap {
                          .asFunction(env));
 
         js::Context<js::realmjsi::Types>::register_invalidator([] {
-            // Ensure the static constructor is destructed when the runtime goes away.
-            // This is to avoid the reassignment of s_ctor throwing because the runtime has disappeared.
+            // Ensure the static constructor and JSI String reference are destructed when the runtime goes away.
+            // This is to avoid the reassignment throwing because the runtime has disappeared.
             s_ctor.reset();
+            s_js_internal_field_name.reset();
         });
 
         for (auto&& [name, prop] : s_type.static_properties) {
@@ -490,9 +495,11 @@ class ObjectWrap {
 
     static Internal* get_internal(JsiEnv env, const JsiObj& object)
     {
-        static const auto js_internal_field = fbjsi::String::createFromAscii(env, g_internal_field);
+        if (!s_js_internal_field_name) {
+            s_js_internal_field_name = fbjsi::String::createFromAscii(env, g_internal_field);
+        }
 
-        auto internal = object->getProperty(env, js_internal_field);
+        auto internal = object->getProperty(env, *s_js_internal_field_name);
         if (internal.isUndefined()) {
             // In the case of a user opening a Realm with a class-based model,
             // the user defined constructor will get called before the "internal" property has been set.
@@ -665,7 +672,8 @@ class ObjectWrap {
 } // namespace realmjsi
 
 template <typename ClassType>
-class ObjectWrap<realmjsi::Types, ClassType> : public realm::js::realmjsi::ObjectWrap<ClassType> {};
+class ObjectWrap<realmjsi::Types, ClassType> : public realm::js::realmjsi::ObjectWrap<ClassType> {
+};
 
 template <realmjsi::ArgumentsMethodType F>
 fbjsi::Value wrap(fbjsi::Runtime& rt, const fbjsi::Value& thisVal, const fbjsi::Value* args, size_t count)