stockholm/lib/haskell.nix
2021-03-15 01:46:50 +01:00

52 lines
1.4 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 }:
pkgs.writeText name (substitutePkgs' {
inherit pkgs;
sourceDescription =
if callsite != null then
"${name} in ${toString callsite}"
else
"${name} from ${toString path}";
text = readFile path;
});
substitutePkgs' = { pkgs, sourceDescription, text }:
let
f = s:
let
parse = match "(.*)([{]-pkg(:([^}]+))?-[}]\"([^\"]+)\")(.*)" s;
prefix = elemAt parse 0;
pname = if elemAt parse 3 != null then elemAt parse 3 else exename;
exename = elemAt parse 4;
suffix = elemAt parse 5;
pkg = pkgs.${pname} or null;
substitute =
if pkg != null then
"${pkg}/bin/${exename}"
else
trace (toString [
"lib.haskell.replacePkg:"
"warning:"
"while deriving ${sourceDescription}:"
"no substitute found for ${elemAt parse 1}"
])
exename;
in
if parse == null then
s
else
f (prefix + toJSON substitute + suffix);
in
f text;
}