Bug in Files.isSameFile(Path,Path)

[WarnerJan Veldhuis]

Hello nio-dev list,

I ran into a strange bug today, and Stuart Marks told me (cos I asked 
him on Twitter) to run this by you. Trying to be a complete as I can here.

My Windows machine has an S: drive that points to a WebDAV location 
(https://****.stackstorage.com/remote.php/webdav (identifier removed)) 
and has been mapped via "Map Network Drive". I can use the drive in 
Windows with no problems.

Now, in my code I have two Path objects both pointing to different files 
on said S: drive. When I run path1.equals(path2) it returns false as 
expected. When I run Files.isSameFile(path1, path2), it returns true, 
which is unexpected.

This is the code I use: (imports omitted for brevity)

class FilesTestCase {
     public static void main(String[] args) {
         try {
System.out.println(System.getProperty("java.version"));
             Path file1 = Paths.get("s:/subfolder/file 1.csv");
             Path file2 = Paths.get("s:/subfolder/file 2.csv");
             System.out.println("equals: " + file1.equals(file2));
             System.out.println("is same file: " + 
Files.isSameFile(file1, file2));
         }
         catch (IOException e) {
             e.printStackTrace();
         }
     }
}

The output is :
16-ea
equals: false
is same file: true

I expect the output of "is same file" also to be false.

- The test case is run on a Windows 10 Pro machine, fully patched. The 
JDK used was 8 to 16, and they all show the same symptoms.
- So far I could only reproduce this behaviour on a WebDAV drive. This 
problem does not occur on "normal" networked drives. I have tried this 
on my mapped NAS drives, which is mapped via UNC as \\nas\share, and 
then Files::isSameFile returns false as expected.

I hope I could make clear what I found. If there is anything you need 
from me, please ask.

Kind regards,

WarnerJan Veldhuis