url: modify pathToFileURL to handle extended UNC path

PR-URL: #54262
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/url.js

@@ -1530,7 +1530,12 @@ function pathToFileURL(filepath, options = kEmptyObject) {
   if ((windows ?? isWindows) && StringPrototypeStartsWith(filepath, '\\\\')) {
     const outURL = new URL('file://');
     // UNC path format: \\server\share\resource
-    const hostnameEndIndex = StringPrototypeIndexOf(filepath, '\\', 2);
+    // Handle extended UNC path and standard UNC path
+    // "\\?\UNC\" path prefix should be ignored.
+    // Ref: https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation
+    const isExtendedUNC = StringPrototypeStartsWith(filepath, '\\\\?\\UNC\\');
+    const prefixLength = isExtendedUNC ? 8 : 2;
+    const hostnameEndIndex = StringPrototypeIndexOf(filepath, '\\', prefixLength);
     if (hostnameEndIndex === -1) {
       throw new ERR_INVALID_ARG_VALUE(
         'path',
@@ -1545,7 +1550,7 @@ function pathToFileURL(filepath, options = kEmptyObject) {
         'Empty UNC servername',
       );
     }
-    const hostname = StringPrototypeSlice(filepath, 2, hostnameEndIndex);
+    const hostname = StringPrototypeSlice(filepath, prefixLength, hostnameEndIndex);
     outURL.hostname = domainToASCII(hostname);
     outURL.pathname = encodePathChars(
       RegExpPrototypeSymbolReplace(backslashRegEx, StringPrototypeSlice(filepath, hostnameEndIndex), '/'),

test/parallel/test-url-pathtofileurl.js

@@ -104,8 +104,12 @@ const windowsTestCases = [
   { path: 'C:\\€', expected: 'file:///C:/%E2%82%AC' },
   // Rocket emoji (non-BMP code point)
   { path: 'C:\\🚀', expected: 'file:///C:/%F0%9F%9A%80' },
+  // Local extended path
+  { path: '\\\\?\\C:\\path\\to\\file.txt', expected: 'file:///C:/path/to/file.txt' },
   // UNC path (see https://docs.microsoft.com/en-us/archive/blogs/ie/file-uris-in-windows)
   { path: '\\\\nas\\My Docs\\File.doc', expected: 'file://nas/My%20Docs/File.doc' },
+  // Extended UNC path
+  { path: '\\\\?\\UNC\\server\\share\\folder\\file.txt', expected: 'file://server/share/folder/file.txt' },
 ];
 const posixTestCases = [
   // Lowercase ascii alpha