Network paths don't work after 3.4.0

[BananaMasterz]

Running the following code in dart 3.4.0 on WINDOWS raises PathNotFoundException

import 'dart:io';

void main() async {
  print(await File(r'\\my_srv\some_path\test.txt').exists());
  File(r'\\my_srv\some_path\test.txt').copy(r'C:\path\test.txt');
}

but works fine in earlier versions (like 3.3.4 and 3.0.0).

I see there have been some changes like this one (maybe some more) that could be the cause.

I also see that there are not tests set up for network paths so this isn't caught.

Finally I'm not sure why File().exists()) returns true but .copy() can't see the file... shouldn't both methods resolve the paths in the same manner?

This is my OS:

Edition	Windows 11 Pro
Version	23H2
Installed on	‎27/‎3/‎2024
OS build	22631.3737

[dart-github-bot]

Labels: area-vm, type-bug
Summary: The user reports that network paths in Dart code, which worked in earlier versions, now throw PathNotFoundException in Dart 3.4.0 on Windows. The issue appears related to recent changes in the Dart SDK, and the user notes a lack of tests for network paths.

[devoncarew]

cc @mraleph @brianquinlan

[mraleph]

Yeah it was c2e9cee that broke this.

Well, our handling of long UNC paths apparently was always broken and the change in question simply forced copy to use it - which revealed its bugyness.

I am going to fix this. I also realized that File::Copy forces wrong path into "long" format. It is supposed to force destination into long form - but instead forces source, which makes no sense.

Need to fix that as well and write a test.

[mraleph]

I think this should fix it: https://dart-review.googlesource.com/c/sdk/+/372400 - will finish it up tomorrow.