l3build install with a UNC --texmfhome \\server\share installs in the wrong place

[chrullrich]

The package is fontspec from git, d0ebbc73.

> l3build install --texmfhome \\server\share\TeXMF
Current version (from first entry in CHANGES.md): 2.8a
A subdirectory or file \\server\share\TeXMF already exists.
This is pdfTeX, Version 3.141592653-2.6-1.40.24 (MiKTeX 22.3) (preloaded format=pdftex.fmt)
 restricted \write18 enabled.
entering extended mode

So far, so good.

> dir \\server\share\TeXMF\tex\latex\fontspec
 Volume in drive \\server\share is Shared
 Volume Serial Number is 1234-5678

 Directory of \\server\share\TeXMF\tex\latex

File Not Found

Nothing there, that is, the fontspec directory is missing.

However (still in the directory with the package sources):

> dir /b UNC\server\share\TeXMF\tex\latex\fontspec
fontspec-luatex.sty
...

There is a subdirectory UNC in the current directory, with the whole actual UNC path underneath. This looks like l3build got the redirector path from somewhere (the NT path for \\server\share is \\?\UNC\server\share) and thought it was a relative path, so it ended up appending it to the current directory.

>texlua l3build.lua version

l3build: A testing and building system for LaTeX

Release 2022-04-19
Copyright (C) 2014-2021 The LaTeX Project

[chrullrich]

Funny thing: If I make UNC\server\share\TeXMF a directory symlink to \\server\share\TeXMF, the installation ends up where I want it because the wrong path now points to the right one.

[Edit: For clarity: I literally mean "funny"; this is not a particular behavior of l3build.]

[josephwright]

I wonder if this is 'us' or an issue with the Lua library - @zauguin any idea?

[josephwright]

@zauguin I get a feeling this is one for me :)