win,fs: use namespaced path in absolute symlinks

Use the namespaced (with the \\?\ prefix) paths for symlink targets when
the path is absolute. This allows creation of symlinks to files with
long filenames.

Fixes: nodejs#27795

lib/internal/fs/utils.js

@@ -302,6 +302,10 @@ function preprocessSymlinkDestination(path, type, linkPath) {
     path = pathModule.resolve(linkPath, '..', path);
     return pathModule.toNamespacedPath(path);
   }
+  if (pathModule.isAbsolute(path)) {
+    // If the path is absolute, use the \\?\-prefix to enable long filenames
+    return pathModule.toNamespacedPath(path);
+  }
   // Windows symlinks don't tolerate forward slashes.
   return ('' + path).replace(/\//g, '\\');
 }

test/parallel/test-fs-symlink-longpath.js

@@ -0,0 +1,29 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const path = require('path');
+const fs = require('fs');
+
+const tmpdir = require('../common/tmpdir');
+tmpdir.refresh();
+const tmpDir = tmpdir.path;
+const longPath = path.join(...[tmpDir].concat(Array(30).fill('1234567890')));
+fs.mkdirSync(longPath, { recursive: true });
+
+// Test if we can have symlinks to files and folders with long filenames
+const targetDirtectory = path.join(longPath, 'target-directory');
+fs.mkdirSync(targetDirtectory);
+const pathDirectory = path.join(tmpDir, 'new-directory');
+fs.symlink(targetDirtectory, pathDirectory, 'dir', common.mustCall((err) => {
+  assert.ifError(err);
+  assert(fs.existsSync(pathDirectory));
+}));
+
+const targetFile = path.join(longPath, 'target-file');
+fs.writeFileSync(targetFile, 'data');
+const pathFile = path.join(tmpDir, 'new-file');
+fs.symlink(targetFile, pathFile, common.mustCall((err) => {
+  assert.ifError(err);
+  assert(fs.existsSync(pathFile));
+}));