win, fs: detect if symlink target is a directory

On Windows creating a symlink to a directory will not work unless extra
'dir' parameter is passed. This adds a check if link target is a
directory, and if so automatically use 'dir' when creating symlink.

PR-URL: https://github.com/nodejs/node/pull/23724
Refs: https://github.com/nodejs/node/pull/23691
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

1 files changed, 32 insertions, 1 deletions

diff --git a/lib/fs.js b/lib/fs.js
index 5915083db9..2e4bdc8964 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -905,16 +905,47 @@ function symlink(target, path, type_, callback_) {
   validatePath(target, 'target');
   validatePath(path);
 
-  const flags = stringToSymlinkType(type);
   const req = new FSReqCallback();
   req.oncomplete = callback;
 
+  if (isWindows && type === null) {
+    let absoluteTarget;
+    try {
+      // Symlinks targets can be relative to the newly created path.
+      // Calculate absolute file name of the symlink target, and check
+      // if it is a directory. Ignore resolve error to keep symlink
+      // errors consistent between platforms if invalid path is
+      // provided.
+      absoluteTarget = pathModule.resolve(path, '..', target);
+    } catch { }
+    if (absoluteTarget !== undefined) {
+      stat(absoluteTarget, (err, stat) => {
+        const resolvedType = !err && stat.isDirectory() ? 'dir' : 'file';
+        const resolvedFlags = stringToSymlinkType(resolvedType);
+        binding.symlink(preprocessSymlinkDestination(target,
+                                                     resolvedType,
+                                                     path),
+                        pathModule.toNamespacedPath(path), resolvedFlags, req);
+      });
+      return;
+    }
+  }
+
+  const flags = stringToSymlinkType(type);
   binding.symlink(preprocessSymlinkDestination(target, type, path),
                   pathModule.toNamespacedPath(path), flags, req);
 }
 
 function symlinkSync(target, path, type) {
   type = (typeof type === 'string' ? type : null);
+  if (isWindows && type === null) {
+    try {
+      const absoluteTarget = pathModule.resolve(path, '..', target);
+      if (statSync(absoluteTarget).isDirectory()) {
+        type = 'dir';
+      }
+    } catch { }
+  }
   target = toPathIfFileURL(target);
   path = toPathIfFileURL(path);
   validatePath(target, 'target');