From 08bc36248fe2f92e8881a1aef559122c3d5824a6 Mon Sep 17 00:00:00 2001
From: Riccardo Cipolleschi <cipolleschi@fb.com>
Date: Fri, 24 Nov 2023 03:45:24 -0800
Subject: [PATCH] Unify usage of USE_HERMES flag (#41625)

Summary:

To tell React Native whether we are building with hermes or not on iOS, we were using 2 different build time flags:
- USE_HERMES
- RCT_USE_HERMES

The first was widely used by the OSS use case, while the latter was set internally.
Worse than that, their default values were the opposite and we were never setting the RCT_USE_HERMES explicitly with Cocoapods, while there was some piece of code that was trying to "smartly" detect whether Hermes was included or not.

This change unifies the behavior, removing the "smartness" in favor od a declarative approach.

## Changelog:
[Internal] - Unify the USE_HERMES flags

Differential Revision: D51549284
---
 packages/react-native/React-Core.podspec             |  3 ++-
 .../react-native/React/CxxBridge/RCTCxxBridge.mm     | 12 ++----------
 2 files changed, 4 insertions(+), 11 deletions(-)

diff --git a/packages/react-native/React-Core.podspec b/packages/react-native/React-Core.podspec
index 101b5e9cc10056..e2b1ed82b7622b 100644
--- a/packages/react-native/React-Core.podspec
+++ b/packages/react-native/React-Core.podspec
@@ -22,6 +22,7 @@ socket_rocket_version = '0.7.0'
 boost_compiler_flags = '-Wno-documentation'
 
 use_hermes = ENV['USE_HERMES'] == nil || ENV['USE_HERMES'] == '1'
+use_hermes_flag = use_hermes ? "-DUSE_HERMES=1" : ""
 
 header_subspecs = {
   'CoreModulesHeaders'          => 'React/CoreModules/**/*.h',
@@ -63,7 +64,7 @@ Pod::Spec.new do |s|
   s.platforms              = min_supported_versions
   s.source                 = source
   s.resource_bundle        = { "RCTI18nStrings" => ["React/I18n/strings/*.lproj"]}
-  s.compiler_flags         = folly_compiler_flags + ' ' + boost_compiler_flags
+  s.compiler_flags         = folly_compiler_flags + ' ' + boost_compiler_flags + ' ' + use_hermes_flag
   s.header_dir             = "React"
   s.framework              = "JavaScriptCore"
   s.pod_target_xcconfig    = {
diff --git a/packages/react-native/React/CxxBridge/RCTCxxBridge.mm b/packages/react-native/React/CxxBridge/RCTCxxBridge.mm
index af931fd45ca10f..03aa3d0654c2a8 100644
--- a/packages/react-native/React/CxxBridge/RCTCxxBridge.mm
+++ b/packages/react-native/React/CxxBridge/RCTCxxBridge.mm
@@ -41,15 +41,7 @@
 #import <jsireact/JSIExecutor.h>
 #import <reactperflogger/BridgeNativeModulePerfLogger.h>
 
-#ifndef RCT_USE_HERMES
-#if __has_include(<reacthermes/HermesExecutorFactory.h>)
-#define RCT_USE_HERMES 1
-#else
-#define RCT_USE_HERMES 0
-#endif
-#endif
-
-#if RCT_USE_HERMES
+#if USE_HERMES
 #import <reacthermes/HermesExecutorFactory.h>
 #else
 #import "JSCExecutorFactory.h"
@@ -423,7 +415,7 @@ - (void)start
     }
     if (!executorFactory) {
       auto installBindings = RCTJSIExecutorRuntimeInstaller(nullptr);
-#if RCT_USE_HERMES
+#if USE_HERMES
       executorFactory = std::make_shared<HermesExecutorFactory>(installBindings);
 #else
       executorFactory = std::make_shared<JSCExecutorFactory>(installBindings);