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# nixLib - A library of nix functions for vhack.eu
#
# Copyright (C) 2025 Benedikt Peetz <benedikt.peetz@b-peetz.de>
# SPDX-License-Identifier: LGPL-3.0-or-later
#
# This file is part of vhack.eu's nix library.
#
# You should have received a copy of the License along with this program.
# If not, see <https://www.gnu.org/licenses/gpl-3.0.txt>.
{warn}:
# Adapted from this: https://github.com/NixOS/nixpkgs/blob/1814b56453c91192f6d5a6276079948f9fe96c18/pkgs/top-level/by-name-overlay.nix
# This file should not depend on `pkgs` and thus not use `lib`.
{
baseDirectory,
fileName ? null,
fileRegex ? null,
finalizeFunction ? name: value: value,
useShards ? true,
}:
assert fileName == null -> fileRegex != null;
assert fileRegex == null -> fileName != null; let
finalFileRegex =
if fileRegex == null
then "^${escapeRegex fileName}$"
else fileRegex;
fileDisplay =
if fileName == null
then "matching ${fileRegex}"
else fileName;
# From nixpkgs/lib {{{
# These functions are taken straight out of the `nixpkgs/lib`.
# We can't depended on `pkgs` (and thus on `lib`), because the `pkgs` module argument
# is only defined in the `nixpkgs` module (which is imported through this function).
mapAttrsToList = f: attrs:
builtins.map (name: f name attrs.${name}) (builtins.attrNames attrs);
stringToCharacters = s: builtins.genList (p: builtins.substring p 1 s) (builtins.stringLength s);
escape = list: builtins.replaceStrings list (map (c: "\\${c}") list);
escapeRegex = escape (stringToCharacters "\\[{()^$?*+|.");
mapAttrs' = f: set: builtins.listToAttrs (map (attr: f attr set.${attr}) (builtins.attrNames set));
nameValuePair = name: value: {inherit name value;};
filterAttrs = pred: set:
builtins.listToAttrs (builtins.concatMap (name: let
v = set.${name};
in
if pred name v
then [(nameValuePair name v)]
else []) (builtins.attrNames set));
# }}}
rawByName = {
baseDirectory,
finalFileRegex,
fileDisplay,
finalizeFunction,
useShards,
}: let
# Takes a list of attrs as input and returns one merged attr set.
flattenAttrs = list:
if builtins.isList list
then
builtins.foldl' (acc: elem:
if builtins.isList elem
# Merging them with `//` is okay here, as we can be sure that the attr names are
# unique (they were separate dictionary after all)
then acc // (flattenAttrs elem)
else acc // elem) {}
list
else list;
# Module files for a single shard
# Type: String -> String -> ListOf Path
namesForShard = shard: type:
if type != "directory"
then warn "Ignored non-directory, whilst importing by-name directory (${fileDisplay}): '${shard}'" {}
else if useShards
then namesForElementShard shard type
else namesForElementDirect shard type;
# Type: String -> String -> ListOf Path
mkPath = shard: name: toplevelType: let
rawPath = baseDirectory + "/${shard}/${name}";
paths = filterAttrs (_: v: v != null) (mapAttrs' (name: value:
if builtins.match finalFileRegex name != null
then nameValuePair name value
else nameValuePair name null) (builtins.readDir rawPath));
checkPath = path: type:
if builtins.pathExists "${rawPath}/${path}"
then
if toplevelType != "directory"
then
# The `namesForShard` function should have already printed a warning.
[null]
else path
else warn "'${builtins.toString path}' does not exist. Skipped" null;
in
if toplevelType != "directory"
then
# The `namesForShard` function should have already printed a warning.
[null]
else if (builtins.attrValues paths) == []
then warn "'${fileDisplay}' did not match anything in ${rawPath}. Skipped" [null]
else mapAttrsToList checkPath paths;
filterNull = list: builtins.filter (value: value != null) list;
# Type: String -> String -> AttrSet
namesForElementShard = shard: _type: (builtins.mapAttrs
(name: type: filterNull (mkPath shard name type))
(builtins.readDir (baseDirectory + "/${shard}")));
# Type: String -> String -> AttrSet
namesForElementDirect = name: type: {"${name}" = filterNull ((mkPath ".") name type);};
# A list of all paths.
output = flattenAttrs (mapAttrsToList namesForShard (builtins.readDir baseDirectory));
in
output;
firstPass = rawByName {
inherit
baseDirectory
finalFileRegex
fileDisplay
finalizeFunction
useShards
;
};
secondPass =
if fileName != null
then
builtins.mapAttrs (name: value: builtins.head value)
(filterAttrs (_: value: value != []) firstPass)
else firstPass;
in
builtins.mapAttrs
finalizeFunction
secondPass
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