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# 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:
{
# This attribute is necessary to allow CI to ensure that all packages defined in `pkgs/by-name`
# don't have an overriding definition in `all-packages.nix` with an empty (`{ }`) second `callPackage` argument.
# It achieves that with an overlay that modifies both `callPackage` and this attribute to signal whether `callPackage` is used
# and whether it's defined by this file here or `all-packages.nix`.
# TODO: This can be removed once `pkgs/by-name` can handle custom `callPackage` arguments without `all-packages.nix` (or any other way of achieving the same result).
# Because at that point the code in ./stage.nix can be changed to not allow definitions in `all-packages.nix` to override ones from `pkgs/by-name` anymore and throw an error if that happens instead.
_internalCallByNamePackageFile = file: self.callPackage file { };
}
// mapAttrs
(name: self._internalCallByNamePackageFile)
packageFiles
|