buildEnv: support force-creating all directories and symlinking only files

[abbradar]

This would simplify, for example, #4577 expression (or maybe there is just another, better way?). Another (more grained) approach would be to add a list argument which specifies directories that should be created and not symlinked.

[abbradar]

This also would be good for abbradar@4ecc6d5 . buildEnv is actually a very good and clean way to create such wrappers in my opinion, apart from this issue.

[peti]

👍 This would be useful, indeed.

[lucabrunox]

I'd go for listing directories that shall not be symlinked.

[peti]

My use-case required all directories to be created for real, because I don't know ahead of time the names of those directories.

[abbradar]

For recent examples of workarounds see https://github.com/NixOS/nixpkgs/blob/master/pkgs/games/dwarf-fortress/wrapper/default.nix#L23. I have quite a bit of those scattered across nixpkgs now.

[vcunat]

Dealing with NixOS/nix#341 will (probably) include implementing buildEnv in C++. After that I assume nixpkgs will just directly use buildEnv from nix. (For now it isn't really important how exactly.)

Hopefully the issue won't be stranded for too long anymore.

[rasendubi]

I've opened a PR that creates directories for all pathsToLink (#16828). While it not exactly follows this proposal, it may fix the issue when names are known ahead of time (pathsToLink = [ "/" "/real/directory" ]).

[vcunat]

Note that we also have symlinkJoin function which is a thin wrapper around the lndir command.

[Profpatsch]

So between @rasendubi’s comment and @vcunat’s comment, can this issue be considered fixed?

[stale]

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