Haskell questions (ihaskell/propagated inputs)

I want to improve the new jupyter (< 2 months old) module, especially with regards to the haskell kernel as I want to hone my haskell skills and jupyter seems nice for it (to run visualizations too).
(For instance to configure the kernels via the kernelspec.json files in some packages instead of setting each parameter manually in the jupyter module New jupyter service · Issue #45697 · NixOS/nixpkgs · GitHub).

I’ve met some problems along the way (with a regularly updated nixos-unstable), hence this “meta” issue.

For instance, I wanted to use ihaskell to generate a kernel.json but I run into How to propagate some binaries in haskell (bug ?) · Issue #47862 · NixOS/nixpkgs · GitHub, aka adding jupyter to ihaskell buildInputs doesn’t seem propagated.

Another strange thing is when running ihaskell as a jupyter kernel, it can’t find ghc-pkg ihaskell can't find ghc-pkg · Issue #47135 · NixOS/nixpkgs · GitHub. It seems that the haskell infra doesn’t propagate haskell basic tools contrary to python, where when you instantiate a python module, python gets in PATH.

Looking for some help/tips to understand my possible mistakes or solve the issues at stake.