esm: avoid import.meta setup costs for unused properties

aduh95 · aduh95 · commit bef06b11df7d · 2025-05-19T12:14:09.000+02:00
PR-URL: #57286 Reviewed-By: Jacob Smith <jacob@frende.me> Reviewed-By: Edy Silva <edigleyssonsilva@gmail.com>
diff --git a/lib/internal/modules/esm/initialize_import_meta.js b/lib/internal/modules/esm/initialize_import_meta.js
@@ -5,8 +5,10 @@ const {
 } = primordials;
 
 const { getOptionValue } = require('internal/options');
-const { fileURLToPath } = require('internal/url');
-const { dirname } = require('path');
+const {
+  setLazyPathHelpers,
+} = internalBinding('modules');
+
 const experimentalImportMetaResolve = getOptionValue('--experimental-import-meta-resolve');
 
 /**
@@ -58,11 +60,9 @@ function initializeImportMeta(meta, context, loader) {
 
   // Alphabetical
   if (StringPrototypeStartsWith(url, 'file:') === true) {
-    // These only make sense for locally loaded modules,
-    // i.e. network modules are not supported.
-    const filePath = fileURLToPath(url);
-    meta.dirname = dirname(filePath);
-    meta.filename = filePath;
+    // dirname
+    // filename
+    setLazyPathHelpers(meta, url);
   }
 
   if (!loader || loader.allowImportMetaResolve) {
diff --git a/src/env_properties.h b/src/env_properties.h
@@ -124,6 +124,7 @@
   V(destroyed_string, "destroyed")                                             \
   V(detached_string, "detached")                                               \
   V(dh_string, "DH")                                                           \
+  V(dirname_string, "dirname")                                                 \
   V(divisor_length_string, "divisorLength")                                    \
   V(dns_a_string, "A")                                                         \
   V(dns_aaaa_string, "AAAA")                                                   \
@@ -327,6 +328,7 @@
     "export * from 'original'; export { default } from 'original'; export "    \
     "const __esModule = true;")                                                \
   V(require_string, "require")                                                 \
+  V(resolve_string, "resolve")                                                 \
   V(resource_string, "resource")                                               \
   V(result_string, "result")                                                   \
   V(retry_string, "retry")                                                     \
diff --git a/src/node_modules.cc b/src/node_modules.cc
@@ -30,6 +30,7 @@ using v8::NewStringType;
 using v8::Object;
 using v8::ObjectTemplate;
 using v8::Primitive;
+using v8::PropertyCallbackInfo;
 using v8::String;
 using v8::Undefined;
 using v8::Value;
@@ -529,6 +530,77 @@ void GetCompileCacheDir(const FunctionCallbackInfo<Value>& args) {
           .ToLocalChecked());
 }
 
+static void PathHelpersLazyGetter(Local<v8::Name> name,
+                                  const PropertyCallbackInfo<Value>& info) {
+  Isolate* isolate = info.GetIsolate();
+  // This getter has no JavaScript function representation and is not
+  // invoked in the creation context.
+  // When this getter is invoked in a vm context, the `Realm::GetCurrent(info)`
+  // returns a nullptr and retrieve the creation context via `this` object and
+  // get the creation Realm.
+  Local<Value> receiver_val = info.This();
+  if (!receiver_val->IsObject()) {
+    THROW_ERR_INVALID_INVOCATION(isolate);
+    return;
+  }
+  Local<Object> receiver = receiver_val.As<Object>();
+  Local<Context> context;
+  if (!receiver->GetCreationContext().ToLocal(&context)) {
+    THROW_ERR_INVALID_INVOCATION(isolate);
+    return;
+  }
+  Environment* env = Environment::GetCurrent(context);
+
+  node::Utf8Value url(isolate, info.Data());
+  auto file_url = ada::parse(url.ToStringView());
+  CHECK(file_url);
+  auto file_path = url::FileURLToPath(env, *file_url);
+  CHECK(file_path.has_value());
+  std::string_view ret_view = file_path.value();
+
+  node::Utf8Value utf8name(isolate, name);
+  auto plain_name = utf8name.ToStringView();
+  if (plain_name == "dirname") {
+#ifdef _WIN32
+#define PATH_SEPARATOR '\\'
+#else
+#define PATH_SEPARATOR '/'
+#endif
+    auto index = ret_view.rfind(PATH_SEPARATOR);
+    CHECK(index != std::string_view::npos);
+    ret_view.remove_suffix(ret_view.size() - index);
+#undef PATH_SEPARATOR
+  }
+  Local<Value> ret;
+  if (!ToV8Value(context, ret_view, isolate).ToLocal(&ret)) {
+    return;
+  }
+  info.GetReturnValue().Set(ret);
+}
+void InitImportMetaPathHelpers(const FunctionCallbackInfo<Value>& args) {
+  // target, url, shouldSetDirnameAndFilename, resolve
+  CHECK_GE(args.Length(), 2);
+  CHECK(args[0]->IsObject());
+  CHECK(args[1]->IsString());
+
+  Isolate* isolate = args.GetIsolate();
+  Local<Context> context = isolate->GetCurrentContext();
+  Environment* env = Environment::GetCurrent(context);
+
+  auto target = args[0].As<Object>();
+
+  // N.B.: Order is important to keep keys in alphabetical order.
+  if (target
+          ->SetLazyDataProperty(
+              context, env->dirname_string(), PathHelpersLazyGetter, args[1])
+          .IsNothing() ||
+      target
+          ->SetLazyDataProperty(
+              context, env->filename_string(), PathHelpersLazyGetter, args[1])
+          .IsNothing())
+    return;
+}
+
 void BindingData::CreatePerIsolateProperties(IsolateData* isolate_data,
                                              Local<ObjectTemplate> target) {
   Isolate* isolate = isolate_data->isolate();
@@ -547,6 +619,7 @@ void BindingData::CreatePerIsolateProperties(IsolateData* isolate_data,
   SetMethod(isolate, target, "enableCompileCache", EnableCompileCache);
   SetMethod(isolate, target, "getCompileCacheDir", GetCompileCacheDir);
   SetMethod(isolate, target, "flushCompileCache", FlushCompileCache);
+  SetMethod(isolate, target, "setLazyPathHelpers", InitImportMetaPathHelpers);
 }
 
 void BindingData::CreatePerContextProperties(Local<Object> target,
@@ -581,6 +654,7 @@ void BindingData::RegisterExternalReferences(
   registry->Register(EnableCompileCache);
   registry->Register(GetCompileCacheDir);
   registry->Register(FlushCompileCache);
+  registry->Register(InitImportMetaPathHelpers);
 }
 
 }  // namespace modules
