module: ensure relative requires work from deleted directories

PR-URL: #42384
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/modules/cjs/loader.js

@@ -130,9 +130,10 @@ const { validateString } = require('internal/validators');
 const pendingDeprecation = getOptionValue('--pending-deprecation');
 
 const {
-  CHAR_FORWARD_SLASH,
   CHAR_BACKWARD_SLASH,
-  CHAR_COLON
+  CHAR_COLON,
+  CHAR_DOT,
+  CHAR_FORWARD_SLASH,
 } = require('internal/constants');
 
 const {
@@ -538,7 +539,12 @@ function resolveExports(nmPath, request) {
   }
 }
 
-const trailingSlashRegex = /(?:^|\/)\.?\.$/;
+/**
+ * @param {string} request a relative or absolute file path
+ * @param {Array<string>} paths file system directories to search as file paths
+ * @param {boolean} isMain if the request is the main app entry point
+ * @returns {string | false}
+ */
 Module._findPath = function(request, paths, isMain) {
   const absoluteRequest = path.isAbsolute(request);
   if (absoluteRequest) {
@@ -553,18 +559,42 @@ Module._findPath = function(request, paths, isMain) {
     return entry;
 
   let exts;
-  let trailingSlash = request.length > 0 &&
-    StringPrototypeCharCodeAt(request, request.length - 1) ===
-    CHAR_FORWARD_SLASH;
-  if (!trailingSlash) {
-    trailingSlash = RegExpPrototypeExec(trailingSlashRegex, request) !== null;
+  const trailingSlash = request.length > 0 &&
+    (StringPrototypeCharCodeAt(request, request.length - 1) === CHAR_FORWARD_SLASH || (
+      StringPrototypeCharCodeAt(request, request.length - 1) === CHAR_DOT &&
+      (
+        request.length === 1 ||
+        StringPrototypeCharCodeAt(request, request.length - 2) === CHAR_FORWARD_SLASH ||
+        (StringPrototypeCharCodeAt(request, request.length - 2) === CHAR_DOT && (
+          request.length === 2 ||
+          StringPrototypeCharCodeAt(request, request.length - 3) === CHAR_FORWARD_SLASH
+        ))
+      )
+    ));
+
+  const isRelative = StringPrototypeCharCodeAt(request, 0) === CHAR_DOT &&
+    (
+      request.length === 1 ||
+      StringPrototypeCharCodeAt(request, 1) === CHAR_FORWARD_SLASH ||
+      (isWindows && StringPrototypeCharCodeAt(request, 1) === CHAR_BACKWARD_SLASH) ||
+      (StringPrototypeCharCodeAt(request, 1) === CHAR_DOT && ((
+        request.length === 2 ||
+        StringPrototypeCharCodeAt(request, 2) === CHAR_FORWARD_SLASH) ||
+        (isWindows && StringPrototypeCharCodeAt(request, 2) === CHAR_BACKWARD_SLASH)))
+    );
+  let insidePath = true;
+  if (isRelative) {
+    const normalizedRequest = path.normalize(request);
+    if (StringPrototypeStartsWith(normalizedRequest, '..')) {
+      insidePath = false;
+    }
   }
 
   // For each path
   for (let i = 0; i < paths.length; i++) {
-    // Don't search further if path doesn't exist
+    // Don't search further if path doesn't exist and request is inside the path
     const curPath = paths[i];
-    if (curPath && _stat(curPath) < 1) continue;
+    if (insidePath && curPath && _stat(curPath) < 1) continue;
 
     if (!absoluteRequest) {
       const exportsResolved = resolveExports(curPath, request);

test/parallel/test-require-enoent-dir.js

@@ -0,0 +1,30 @@
+'use strict';
+
+const common = require('../common');
+const tmpdir = require('../common/tmpdir');
+const assert = require('assert');
+const fs = require('fs');
+const path = require('path');
+
+tmpdir.refresh();
+
+const fooPath = path.join(tmpdir.path, 'foo.cjs');
+fs.writeFileSync(fooPath, '');
+
+const dirPath = path.join(tmpdir.path, 'delete_me');
+fs.mkdirSync(dirPath, {
+  recursive: true
+});
+
+const barPath = path.join(dirPath, 'bar.cjs');
+fs.writeFileSync(barPath, `
+    module.exports = () => require('../foo.cjs').call()
+`);
+
+const foo = require(fooPath);
+const unique = Symbol('unique');
+foo.call = common.mustCall(() => unique);
+const bar = require(barPath);
+
+fs.rmSync(dirPath, { recursive: true });
+assert.strict.equal(bar(), unique);