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Nixpkgs Architecture Team Meeting #21

Past meeting notes
Recording
Matrix announcement
Recorded by: @infinisil
Lead by: @infinisil
Meeting notes by: @Ericson2314
Present members: @Ericson2314 @infinisil @roberth @growpotkin

Notes

NixOS/nix#7447

Should we do full stat?
- @Ericson2314: Seems like a good idea if it is just the info in Nix's restricted file system model.
- @growpotkin: Should be a separate PR/builtin
- @growpotkin: Playing devil's advocate, sometimes useful to check executable on direction in particular
  - @Ericson2314: Oh wait, that convinces me the opposite! Directories do not have exe bit in Nix's model, so we shouldn't be able to see that with primop.
- avoiding a derivation if it's not necessary to fix up the permission bitsexe
- @infinisil: Use case for checking executable bit at eval time?
- @infinisil: Alternative: Make the primop internal, not accessible at first
  - @roberth: Can be done, but a bit of a shame not, do have an issue for a path type builtin
- @growpotkin: Some cost to allocating attribute for returning multiple properties
- @roberth: Let's keep it simple with pathType for now, can have pathInfo later.
What is the perf situation?
- Linux is fast regardless
  - Fast on growpotkin's machine either way
  - @Ericson2314: Most file systems will return the info with the dir entry and so this change is dead code.
- Needs to be tested on Darwin
- @Ericson2314: Scared that we still have no idea what made things slow on Darwin.
- @growpotkin: Never scared, arms crossed

nixpkgs-architecture/simple-package-paths#22

Scans Nix files for paths
Prints files which are only referenced from pkgs/top-level/all-packages.nix
@infinisil: Should interface be general?
- @wanja: Fine to be one off
- @Ericson2314: Agreed. The code can be nice when it's easy to do so -- ready to go in a library e.g., but the CLI we can not bother to generalize prematurely.

Action items

@Ericson2314 and @growpotkin will continue with NixOS/nix#7447, especially testing it on Darwin
@infinisil will continue writing the tooling in nixpkgs-architecture/simple-package-paths#22
@Ericson2314 will talk to the Cargo people on Zulip about sharding. @infinisil will have an account so @Ericson2314 can ping and not be single point of failure.
- Ask git too, maybe. They do for .git/objects.