Remove default payload factory static storage (#59517)

Summary:
Pull Request resolved: #59517

Return the stateless payload callable directly instead of caching a std::function, avoiding its dynamic static initialization and teardown without changing the factory API or payload behaviour.

Changelog: [Internal]

___

landed-with-radar-review

Differential Revision: D127583053

fbshipit-source-id: ac9e3b0dd13ef749b34a185d120ec09ca81a7530

Author: javache

packages/react-native/ReactCommon/react/renderer/core/EventEmitter.cpp

@@ -44,9 +44,7 @@ std::mutex& EventEmitter::DispatchMutex() {
 }
 
 ValueFactory EventEmitter::defaultPayloadFactory() {
-  static auto payloadFactory =
-      ValueFactory{[](jsi::Runtime& runtime) { return jsi::Object(runtime); }};
-  return payloadFactory;
+  return [](jsi::Runtime& runtime) { return jsi::Object(runtime); };
 }
 
 EventEmitter::EventEmitter(

packages/react-native/ReactCommon/react/renderer/core/tests/EventEmitterTest.cpp

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <gtest/gtest.h>
+#include <hermes/hermes.h>
+#include <react/renderer/core/EventEmitter.h>
+
+namespace facebook::react {
+
+TEST(EventEmitterTest, defaultPayloadFactoryCreatesFreshEmptyObjects) {
+  auto runtime = hermes::makeHermesRuntime();
+  auto factory = EventEmitter::defaultPayloadFactory();
+
+  auto first = factory(*runtime).getObject(*runtime);
+  EXPECT_EQ(first.getPropertyNames(*runtime).size(*runtime), 0u);
+  first.setProperty(*runtime, "mutation", 42);
+  EXPECT_EQ(first.getProperty(*runtime, "mutation").getNumber(), 42);
+
+  auto second = factory(*runtime).getObject(*runtime);
+  EXPECT_EQ(second.getPropertyNames(*runtime).size(*runtime), 0u);
+  EXPECT_FALSE(second.hasProperty(*runtime, "mutation"));
+}
+
+TEST(EventEmitterTest, defaultPayloadFactoryUsesSuppliedRuntime) {
+  auto firstRuntime = hermes::makeHermesRuntime();
+  auto secondRuntime = hermes::makeHermesRuntime();
+  auto factory = EventEmitter::defaultPayloadFactory();
+
+  auto first = factory(*firstRuntime).getObject(*firstRuntime);
+  first.setProperty(*firstRuntime, "mutation", 42);
+
+  auto second = factory(*secondRuntime).getObject(*secondRuntime);
+  EXPECT_EQ(second.getPropertyNames(*secondRuntime).size(*secondRuntime), 0u);
+  EXPECT_FALSE(second.hasProperty(*secondRuntime, "mutation"));
+  EXPECT_EQ(first.getProperty(*firstRuntime, "mutation").getNumber(), 42);
+}
+
+} // namespace facebook::react