Windows file `URL` prepends "/" at beginning of `path` property, breaking compatibility

[gregcotten]

For example, initialize a simple file URL and print its path:

let url = URL(fileURLWithPath: "C:/Test")
print(url.path)

In Swift 5.10.1, you get: C:/Test
In Swift 6.0 (August 7 snapshot) you get: /C:/Test

Maybe this is intended, but it definitely breaks my usage of passing file URL paths as arguments into a spawned Process for my build tools.

[jmschonfeld]

@jrflat I believe this is the new behavior of URL, so you might be able to look into this. @gregcotten I'd be interested hearing more about how this breaks your use of Process as I'd expect Process itself should still handle this (as URL.withUnsafeFileSystemRepresentation and FileManager.fileSystemRepresentation which are used to provide file system paths to C APIs should still handle this case and remove the leading slash) so at a minimum we should probably correct Process to account for this (I updated Process to correct the executable path with swiftlang/swift-corelibs-foundation#4999)

[gregcotten]

Interesting! I guess my issue with path being RFC8089 is that it's a rather large change, especially for me :)

I often use someURL.path as a way of communicating a path to a non-Swift party, like calling out to an external process from Swift with a someURL.path as an argument, or in the case of our Electron app, communicating with their JS backend about presenting a save file dialog with a specified path, etc...

[jrflat]

@jmschonfeld Yeah I think we were just discussing there could be merit in moving Windows path logic (replacing / with \, removing leading slash if there's a drive letter) to URL.fileSystemPath, which is vended to URL.path for compatibility. I can look into that.

[dschaefer2]

Any update on this? @ahoppen mentioned it breaks sourcekit-lsp on Windows.

[jrflat]

Yes, apologies for the delay! Opened a PR to resolve the leading slash issue.

I think in the future it could also be a good idea for URL.fileSystemPath to convert all slashes to backslashes on Windows. Although, since URL.fileSystemPath and URL.path are synonymous, and this might further break URL.path compatibility, we'll hold off on that change for now.

[grynspan]

@jrflat Can we get this cherry-picked to release/6.0 for the next dot release?
n/m just saw #983

[jrflat]

Yes for reference this is cherry-picked to release/6.0 in #969 and release/6.0.2 in #983

[ahoppen]

I’m still seeing this behavior in 6.0.2.

print(URL(string: "file:///C:/test.swift")!.path)

prints /C:/test.swift

Was this fix not cherry-picked to 6.0.2 after all

The issue does appear to be fixed on swift-DEVELOPMENT-SNAPSHOT-2024-10-25-a. There doesn’t seem to be any recent Swift 6.0 snapshots available for Windows, so I can’t test that. Just want to make sure that we aren’t unintentionally missing this from release/6.0.

[jrflat]

This was cherry-picked to 6.0.2 in #983, I'll try to find a recent 6.0.2 Windows toolchain to confirm.