Add `builtins.toDir`

[Ericson2314]

We have toFile, readFile, and readDir, this would complete the square. I suppose it would take a attrset of paths and return a store path. Maybe like filterSource, we would need some restriction on the input source in case they are a derivation output that needs to be built? (Though I really hope we can turn builtins.filterSource into contents-addresssed derivations when we need to delay them!)

---

This probably can be solved another way in the meantime, but I would use it move the setup hooks common to every stdenv to $out/nix-support/setup/hook, that we the awful part of stdenv that tries to source an input if it is just a single file can go away.

• Bad stdenv, bad: https://github.com/NixOS/nixpkgs/blob/2ef110ae64a96c0d16df86f8390cfe0af7ff45dc/pkgs/stdenv/generic/setup.sh#L474-L476

• Bare setup hooks: https://github.com/NixOS/nixpkgs/blob/2a19a034313e46134853a655121d45b37ab3cbb6/pkgs/stdenv/generic/default.nix#L55-L69

EDIT: mentioning toDirectory for discoverability. toDir is the consistent name.

[edolstra]

How does it differ from builtins.path?

[Ericson2314]

Let me write an example of what I am thinking:

builtins.toDir "nix-support" {
  "setup-hook" = { 
      executable = false;
      contents = ./pkgs/buils-suport/setup-hooks/foo.sh;
   };
}

builtins.path can't do that, right?

[stale[bot]]

I marked this as stale due to inactivity. → More info

[roberth]

Smells like a lazy tree.

[edolstra]

Yeah, this could be implemented as an InputAccessor, similar to PatchingInputAccessor , that would synthesize a source tree lazily.