src: use v8::Isolate::GetDefaultLocale() to compute navigator.language

Using the Intl API to get the default locale slows down the startup
significantly. This patch uses a new v8 API to get the default locale
directly.

PR-URL: https://github.com/nodejs/node/pull/54279
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/navigator.js

@@ -30,7 +30,7 @@ const {
 } = require('internal/process/per_thread');
 
 const {
-  language,
+  getDefaultLocale,
 } = internalBinding('config');
 
 /**
@@ -104,7 +104,9 @@ class Navigator {
    * @return {string}
    */
   get language() {
-    return language;
+    // The default locale might be changed dynamically, so always invoke the
+    // binding.
+    return getDefaultLocale() || 'en-US';
   }
 
   /**

lib/internal/process/pre_execution.js

@@ -20,10 +20,6 @@ const {
   globalThis,
 } = primordials;
 
-const {
-  Intl,
-} = globalThis;
-
 const {
   getOptionValue,
   refreshOptions,
@@ -333,7 +329,6 @@ function setupNavigator() {
 
   // https://html.spec.whatwg.org/multipage/system-state.html#the-navigator-object
   exposeLazyInterfaces(globalThis, 'internal/navigator', ['Navigator']);
-  internalBinding('config').language = Intl?.Collator().resolvedOptions().locale || 'en-US';
   defineReplaceableLazyAttribute(globalThis, 'internal/navigator', ['navigator'], false);
 }
 

src/node_config.cc

@@ -2,6 +2,7 @@
 #include "memory_tracker.h"
 #include "node.h"
 #include "node_builtins.h"
+#include "node_external_reference.h"
 #include "node_i18n.h"
 #include "node_options.h"
 #include "util-inl.h"
@@ -9,12 +10,23 @@
 namespace node {
 
 using v8::Context;
+using v8::FunctionCallbackInfo;
 using v8::Isolate;
 using v8::Local;
 using v8::Number;
 using v8::Object;
 using v8::Value;
 
+void GetDefaultLocale(const FunctionCallbackInfo<Value>& args) {
+  Isolate* isolate = args.GetIsolate();
+  Local<Context> context = isolate->GetCurrentContext();
+  std::string locale = isolate->GetDefaultLocale();
+  Local<Value> result;
+  if (ToV8Value(context, locale).ToLocal(&result)) {
+    args.GetReturnValue().Set(result);
+  }
+}
+
 // The config binding is used to provide an internal view of compile time
 // config options that are required internally by lib/*.js code. This is an
 // alternative to dropping additional properties onto the process object as
@@ -23,7 +35,7 @@ using v8::Value;
 // Command line arguments are already accessible in the JS land via
 // require('internal/options').getOptionValue('--some-option'). Do not add them
 // here.
-static void Initialize(Local<Object> target,
+static void InitConfig(Local<Object> target,
                        Local<Value> unused,
                        Local<Context> context,
                        void* priv) {
@@ -76,8 +88,15 @@ static void Initialize(Local<Object> target,
 #endif  // NODE_NO_BROWSER_GLOBALS
 
   READONLY_PROPERTY(target, "bits", Number::New(isolate, 8 * sizeof(intptr_t)));
+
+  SetMethodNoSideEffect(context, target, "getDefaultLocale", GetDefaultLocale);
 }  // InitConfig
 
+void RegisterConfigExternalReferences(ExternalReferenceRegistry* registry) {
+  registry->Register(GetDefaultLocale);
+}
+
 }  // namespace node
 
-NODE_BINDING_CONTEXT_AWARE_INTERNAL(config, node::Initialize)
+NODE_BINDING_CONTEXT_AWARE_INTERNAL(config, node::InitConfig)
+NODE_BINDING_EXTERNAL_REFERENCE(config, node::RegisterConfigExternalReferences)

src/node_external_reference.h

@@ -139,6 +139,7 @@ class ExternalReferenceRegistry {
   V(buffer)                                                                    \
   V(builtins)                                                                  \
   V(cares_wrap)                                                                \
+  V(config)                                                                    \
   V(contextify)                                                                \
   V(credentials)                                                               \
   V(encoding_binding)                                                          \