LSP Uris causes headache in Windows Subsystem for Linux

[TimWhiting]

Ran into this with our Koka language server

Here is Daan's comments in our workaround, which should provide a basic understanding of the issue:

-- work around lsp bugs :-(  (we should report this but it seems there are multiple wrong assumptions in both normalization and in uriToFilePath)
-- on Windows, a file path like "\\wsl.localhost\Ubuntu\home\koka\samples\basic\fibonacci.kk"
-- becomes a J.Uri as           "file://wsl.localhost/Ubuntu/home/koka/samples/basic/fibonacci.kk" (note the lost \\ start)
-- and a J.NormalizedUri  as    "file:///wsl.localhostUbuntu/home/koka/samples/basic/fibonacci.kk" (note the lost / before Ubuntu, and added / start)
--
-- here we try to correct that for this specific case so we can at least open
-- files in a WSL file system on Windows
-- (which is important as build on wsl2 is very slow outside the wsl mounted file system)

https://github.com/koka-lang/koka/blob/f48555f1e2ba211f3e86524a15668597cad19118/src/Main/langserver/LanguageServer/Conversions.hs#L151

[michaelpj]

I'm... surprised that it's that broken. I thought people used HLS on windows okay, so I would have thought we would have run into this.

I'm not totally sure how this is supposed to work and I don't have a windows machine to test on, so a PR would be very welcome!

[TimWhiting]

It looks like this is something specific to a configuration where the files are in the WSL filesystem, but vscode is not used in a client(windows)-server(wsl) configuration, instead opening just the windows version of vscode in that folder. I probably don't have the time to look into it soon, but just wanted to write this down as additional information if anyone wonders how to reproduce this.