how to deal with string contexts

[MangoIV]

the issue is as follows:

• for the build time dependencies we want to look up meta/ pname/ ... to find information about our packages
• for this we must be at the nix level, i.e. with access to the attrset that mkDerivation builds
• at this point we know the drvPath so we can query the dependencies
• these dependencies don't necessarily have to be available in the nix level, reason: string contexts; simple example:

pkgs.callPackage ./buildtime-dependencies.nix {} (
  pkgs.runCommand "foo" {} ''cp -r ${pkgs.hello}/bin $out''
)

this package clearly depends on pkgs.hello but bombon doesn't recognize that.

I have not found a solution but a very sad one:

• build meta for all of the packages that might be included; the user would pass a list of package sets and dependencies to build a meta "database" keyed by the drvPath of the derivation
• build the dependency tree of some package separately
• query the "database" against the drvPaths.

[nikstur]

That's a very good observation, thank you! I don't have a clear answer yet how I can/want to solve this.

[arianvp]

We need https://github.com/NixOS/nix/issues/4677

[MangoIV]

https://github.com/wireapp/wire-server/blob/develop/nix/pkg-info.nix https://github.com/wireapp/wire-server/blob/develop/nix/all-toplevel-derivations.nix https://github.com/wireapp/wire-server/blob/develop/hack/bin/Sbom.hs

I’ve made this abomination a while ago. It works but it probably needs a ton of adjustments if you want to use it for anything but wireserver

[MangoIV]

It goes what I described above though.

[arianvp]

because pkgs is actually not a tree but a graph so you

will go around in circle

You could use https://nix.dev/manual/nix/2.18/language/builtins#builtins-genericClosure for this

[MangoIV]

That’s not the only problem though. Nix will also memory leak like crazy. So probably not going to work anyway. You need to be careful what to recurse on. I think I also excluded a couple of attrsets to not look at.