util: add getCwdSafe internal util fn

This function was first implemented in nodejs#46826, but at some point
of the PR implementation this fn was no longer related to the PR.

Refs: nodejs#46826 (comment)
PR-URL: nodejs#48434
Reviewed-By: Jacob Smith <[email protected]>
Reviewed-By: Yagiz Nizipli <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>

Author: jlenon7

lib/internal/modules/esm/resolve.js

@@ -37,6 +37,7 @@ const experimentalNetworkImports =
   getOptionValue('--experimental-network-imports');
 const typeFlag = getOptionValue('--input-type');
 const { URL, pathToFileURL, fileURLToPath, isURL } = require('internal/url');
+const { getCWDURL } = require('internal/util');
 const { canParse: URLCanParse } = internalBinding('url');
 const { legacyMainResolve: FSLegacyMainResolve } = internalBinding('fs');
 const {
@@ -1095,7 +1096,7 @@ function defaultResolve(specifier, context = {}) {
 
   const isMain = parentURL === undefined;
   if (isMain) {
-    parentURL = pathToFileURL(`${process.cwd()}/`).href;
+    parentURL = getCWDURL().href;
 
     // This is the initial entry point to the program, and --input-type has
     // been passed as an option; but --input-type can only be used with

lib/internal/modules/esm/utils.js

@@ -21,7 +21,7 @@ const {
   loadPreloadModules,
   initializeFrozenIntrinsics,
 } = require('internal/process/pre_execution');
-const { pathToFileURL } = require('internal/url');
+const { getCWDURL } = require('internal/util');
 const {
   setImportModuleDynamicallyCallback,
   setInitializeImportMetaObjectCallback,
@@ -195,15 +195,6 @@ function isLoaderWorker() {
 async function initializeHooks() {
   const customLoaderURLs = getOptionValue('--experimental-loader');
 
-  let cwd;
-  try {
-    // `process.cwd()` can fail if the parent directory is deleted while the process runs.
-    cwd = process.cwd() + '/';
-  } catch {
-    cwd = '/';
-  }
-
-
   const { Hooks } = require('internal/modules/esm/hooks');
   const esmLoader = require('internal/process/esm_loader').esmLoader;
 
@@ -220,7 +211,7 @@ async function initializeHooks() {
   loadPreloadModules();
   initializeFrozenIntrinsics();
 
-  const parentURL = pathToFileURL(cwd).href;
+  const parentURL = getCWDURL().href;
   for (let i = 0; i < customLoaderURLs.length; i++) {
     await hooks.register(
       customLoaderURLs[i],

lib/internal/process/esm_loader.js

@@ -9,8 +9,7 @@ const { getOptionValue } = require('internal/options');
 const {
   hasUncaughtExceptionCaptureCallback,
 } = require('internal/process/execution');
-const { pathToFileURL } = require('internal/url');
-const { kEmptyObject } = require('internal/util');
+const { kEmptyObject, getCWDURL } = require('internal/util');
 
 let esmLoader;
 
@@ -23,14 +22,7 @@ module.exports = {
     try {
       const userImports = getOptionValue('--import');
       if (userImports.length > 0) {
-        let cwd;
-        try {
-          // `process.cwd()` can fail if the parent directory is deleted while the process runs.
-          cwd = process.cwd() + '/';
-        } catch {
-          cwd = '/';
-        }
-        const parentURL = pathToFileURL(cwd).href;
+        const parentURL = getCWDURL().href;
         await SafePromiseAllReturnVoid(userImports, (specifier) => esmLoader.import(
           specifier,
           parentURL,

lib/internal/util.js

@@ -358,6 +358,36 @@ function getConstructorOf(obj) {
   return null;
 }
 
+let cachedURL;
+let cachedCWD;
+
+/**
+ * Get the current working directory while accounting for the possibility that it has been deleted.
+ * `process.cwd()` can fail if the parent directory is deleted while the process runs.
+ * @returns {URL} The current working directory or the volume root if it cannot be determined.
+ */
+function getCWDURL() {
+  const { sep } = require('path');
+  const { pathToFileURL } = require('internal/url');
+
+  let cwd;
+
+  try {
+    // The implementation of `process.cwd()` already uses proper cache when it can.
+    // It's a relatively cheap call performance-wise for the most common use case.
+    cwd = process.cwd();
+  } catch {
+    cachedURL ??= pathToFileURL(sep);
+  }
+
+  if (cwd != null && cwd !== cachedCWD) {
+    cachedURL = pathToFileURL(cwd + sep);
+    cachedCWD = cwd;
+  }
+
+  return cachedURL;
+}
+
 function getSystemErrorName(err) {
   const entry = uvErrmapGet(err);
   return entry ? entry[0] : `Unknown system error ${err}`;
@@ -853,6 +883,7 @@ module.exports = {
   filterDuplicateStrings,
   filterOwnProperties,
   getConstructorOf,
+  getCWDURL,
   getInternalGlobal,
   getSystemErrorMap,
   getSystemErrorName,