How to correctly use makeWrapper to change Yarn's --global-folder argument? - nix

Question

I'm trying to write a derivation for a Go project that uses a Makefile to build its frontend with Yarn. As Yarn downloads files, I'm using a fixed derivation hash for networking.
However, Yarn attempts to write to its global package cache in /usr/local or /homeless-shelter, even though neither path exists.
To work around this issue, I tried to use makeWrapper to pass the --global-folder /tmp argument, but while the derivation runs it doesn't seem to be using it, as even --help is ignored.
How can I correctly wrap Yarn, or what other tool can I use to fix this?
cd frontend && yarn install --frozen-lockfile
yarn install v1.22.19
warning Skipping preferred cache folder "/homeless-shelter/.cache/yarn" because it is not writable.
warning Selected the next writable cache folder in the list, will be "/build/.yarn-cache-1000".
[1/4] Resolving packages...
[2/4] Fetching packages...
warning Cannot find a suitable global folder. Tried these: "/usr/local, /homeless-shelter/.yarn"
warning Cannot find a suitable global folder. Tried these: "/usr/local, /homeless-shelter/.yarn"
warning Cannot find a suitable global folder. Tried these: "/usr/local, /homeless-shelter/.yarn"
warning Cannot find a suitable global folder. Tried these: "/usr/local, /homeless-shelter/.yarn"
warning Cannot find a suitable global folder. Tried these: "/usr/local, /homeless-shelter/.yarn"
warning Cannot find a suitable global folder. Tried these: "/usr/local, /homeless-shelter/.yarn"
Done in 24.32s.
Error: ENOENT: no such file or directory, open '/homeless-shelter/.yarnrc'
make: *** [Makefile:218: frontend] Error 1
My config:
{ pkgs ? (
let
inherit (builtins) fetchTree fromJSON readFile;
inherit ((fromJSON (readFile ./flake.lock)).nodes) nixpkgs;
in
import (fetchTree nixpkgs.locked) {
overlays = [];
}
)
}:
with pkgs;
stdenv.mkDerivation rec {
pname = "someapp";
version = "v1.0";
src = fetchFromGitHub {
owner = "someowner";
repo = "someapp";
rev = "ffffffffffffffffffffffffffffffff";
sha256 = "sha256-fffffffffffffffffffffffffffffffff";
};
wrappedYarn = yarn.overrideAttrs (oldAttrs: {
buildInputs = oldAttrs.buildInputs or [] ++ [ makeBinaryWrapper ];
postInstall = oldAttrs.postInstall or "" + ''
wrapProgram $out/bin/yarn \
/*--append-flags "--global-folder /tmp/yarn --global-link /tmp/yarn2"*/
--append-flags "--help"
'';
});
buildInputs = [ go git wrappedYarn gcc gnumake ];
outputHashMode = "flat";
outputHashAlgo = "sha256";
outputHash = lib.fakeHash;
meta = with lib; {
description = "SomeApp";
homepage = "https://github.com/someowner/someapp";
platforms = platforms.linux;
};
}