Is this the right approach?
So the reason you’re running into it is that the find_library function in setuptools (or wherever the python ecosystem has shuffled it to nowadays) won’t work on nix, I recall reading the implementation a few years ago and realizing that it simply cannot find libraries in /nix/store.
Hence, any python package that links to native libraries and is installed using setuptools will always fail to build on nix.
The patch you’re taking from nixpkgs simply hard-codes those paths, replacing the find_library calls. This is enough to fix the problem and allows the build to work. That is probably the best approach - having to patch stuff to work with nix is quite common (I wrote a long-form explanation as to why here if this confuses you).
I remember trying to patch the find_library function once but I don’t recall why I gave up on it. Either way, nix packages are intended to have library paths hard-coded (so that the output stays pure and always uses the same input packages you defined). Using whatever ldd finds at runtime is not desirable, so find_library can’t really be implemented reasonably I think.
I guess this could be contributed to nixpks?
The reason it’s broken for you is because you’re using poetry, which takes the normal python package and tries to link it against your nix libraries. You can’t make this change to the pip package, because it won’t work on other distros.
Given the package on nixpkgs already has those overrides, it will already work if you use nix instead of poetry to install it. What exactly do you intend to contribute to nixpkgs?
You might be able to contribute it to poetry2nix’ built-in override list, I’m not sure exactly what they accept.