stockholm/lib/haskell.nix

55 lines
1.6 KiB
Nix

{ lib }:
with builtins;
rec {
# Derive a file by substituting
# "${pkgs.foo}/bin/foo" for each {-pkg-}"foo", and
# "${pkgs.bar}/bin/foo" for each {-pkg:bar-}"foo".
# If a package doesn't exist, a warning gets printed.
substitutePkgs = name: { callsite ? null, pkgs, path }:
let
sourceDescription =
if callsite != null then
"${name} in ${toString callsite}"
else
"${name} from ${toString path}";
f = dependencies: s:
let
parse = match "(.*)([{]-pkg(:([^}]+))?-[}]\"([^\"]+)\")(.*)" s;
prefix = elemAt parse 0;
pname = if elemAt parse 3 != null then elemAt parse 3 else exename;
exename = elemAt parse 4;
suffix = elemAt parse 5;
pkg = pkgs.${pname} or null;
substitute =
if pkg != null then
"${pkg}/bin/${exename}"
else
trace (toString [
"lib.haskell.substitutePkgs:"
"warning:"
"while deriving ${sourceDescription}:"
"no substitute found for ${elemAt parse 1}"
])
exename;
in
if parse == null then
(pkgs.writeText name s).overrideAttrs (old: {
dependencies =
lib.uniq
(lib.sort (lib.on lib.lessThan (lib.getAttr "name"))
(filter
(lib.ne null)
(old.dependencies or [] ++ dependencies)));
})
else
f (dependencies ++ [pkg]) (prefix + toJSON substitute + suffix);
in
f [] (readFile path);
}