status-react/nix/tools/mkFilter.nix

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{ lib }:
# This Nix expression allows filtering a local directory by
# specifying dirRootsToInclude, dirsToExclude and filesToInclude.
# It also filters out symlinks to result folders created by nix-build,
# as well as backup/swap/generated files.
let
inherit (lib)
any range flatten length sublist cleanSourceFilter
splitString hasPrefix removePrefix concatStringsSep;
inherit (builtins) map match;
mkFilter = {
# primary path under which all files are included, unless excluded
root,
# list of regex expressions to match files to include/exclude
include ? [ ], exclude ? [ ], # has precedence over include
}:
let
# removes superfluous slashes from the path
cleanRoot = "${toString (/. + root)}/";
in path: type:
let
# unpack path: "x/y/.*" => ["x" "x/y" "x/y/.*"]
unpackPath = path:
let
tokens = splitString "/" path;
perms = range 1 (length tokens);
subPaths = builtins.map (x: sublist 0 x tokens) perms;
in builtins.map (x: concatStringsSep "/" x) subPaths;
# accept subdirs from regexes
includeSubdirs = regexes: flatten (map unpackPath regexes);
# checks all regexes in a list against str
matchesRegexes = str: regexes: (map (r: (match r str)) regexes);
# match returns empty list on match
isMatch = x: x == [ ];
# path relative to search root
relPath = removePrefix cleanRoot path;
# check if any of the regexes match the relative path
checkRegexes = regexes: any isMatch (matchesRegexes relPath regexes);
# main check methods
isRootSubdir = hasPrefix cleanRoot path;
isIncluded = checkRegexes (includeSubdirs include);
isExcluded = checkRegexes exclude;
isSCV = !cleanSourceFilter path type;
in
if !isRootSubdir then
# everything outside of root is excluded
false
else if isExcluded || isSCV then
# isExcluded has precedence over isIncluded
false
else
isIncluded;
in mkFilter