nixpkgs/pkgs/top-level/by-name-overlay.nix
Silvan Mosberger f6467c3574 pkgs/by-name: Introduce
This introduces the `pkgs/by-name` directory as proposed by RFC 140.
Included are:
- The implementation to add packages defined in that directory to the
  top-level package scope
- Contributer documentation on how to add packages to it
- A GitHub Actions workflow to check the structure of it on all PRs
2023-09-05 16:10:50 +02:00

51 lines
2.1 KiB
Nix

# This file turns the pkgs/by-name directory (see its README.md for more info) into an overlay that adds all the defined packages.
# No validity checks are done here,
# instead this file is optimised for performance,
# and validity checks are done by CI on PRs.
# Type: Path -> Overlay
baseDirectory:
let
# Because of Nix's import-value cache, importing lib is free
lib = import ../../lib;
inherit (builtins)
readDir
;
inherit (lib.attrsets)
mapAttrs
mapAttrsToList
mergeAttrsList
;
# Package files for a single shard
# Type: String -> String -> AttrsOf Path
namesForShard = shard: type:
if type != "directory" then
# Ignore all non-directories. Technically only README.md is allowed as a file in the base directory, so we could alternatively:
# - Assume that README.md is the only file and change the condition to `shard == "README.md"` for a minor performance improvement.
# This would however cause very poor error messages if there's other files.
# - Ensure that README.md is the only file, throwing a better error message if that's not the case.
# However this would make for a poor code architecture, because one type of error would have to be duplicated in the validity checks and here.
# Additionally in either of those alternatives, we would have to duplicate the hardcoding of "README.md"
{ }
else
mapAttrs
(name: _: baseDirectory + "/${shard}/${name}/package.nix")
(readDir (baseDirectory + "/${shard}"));
# The attribute set mapping names to the package files defining them
# This is defined up here in order to allow reuse of the value (it's kind of expensive to compute)
# if the overlay has to be applied multiple times
packageFiles = mergeAttrsList (mapAttrsToList namesForShard (readDir baseDirectory));
in
# TODO: Consider optimising this using `builtins.deepSeq packageFiles`,
# which could free up the above thunks and reduce GC times.
# Currently this would be hard to measure until we have more packages
# and ideally https://github.com/NixOS/nix/pull/8895
self: super:
mapAttrs (name: file:
self.callPackage file { }
) packageFiles