how about

{
  jupyterLib.mkKernels = {
    python = {
      # the env should be a individual python env
      env = pkgs.python3.withPackages [ ];
      # if env == {}, then env = pkgs.python3.withPackages [ ] ++ [python.pkgs.ipykernel];
      withPackages = [];
      override = {
        ...
      };
    };
    haskell = {
      # env = pkgs.haskellPackages.ghcWithPackages (p: with p; [ ihaskell ]);
      # if env == {}, then env = pkgs.haskellPackages.ghcWithPackages (p: with p; [ ihaskell ]) ++ ghcWithPackages p);
      ghcWithPackages = p: [ p.ihaskell ];
      override = {
        display_name = "Custom Haskell";
      };
    };
    ...
  };
}

how about

{
  jupyterLib.mkKernels = {
    python = {
      # the env should be an individual python env
      env = pkgs.python3.withPackages [ ];
      # if env == {}, then env = pkgs.python3.withPackages [ ] ++ [python.pkgs.ipykernel];
      withPackages = [];
      override = {
        ...
      };
    };
    haskell = {
      # env = pkgs.haskellPackages.ghcWithPackages (p: with p; [ ihaskell ]);
      # if env == {}, then env = pkgs.haskellPackages.ghcWithPackages (p: with p; [ ihaskell ]) ++ ghcWithPackages p);
      ghcWithPackages = p: [ p.ihaskell ];
      override = {
        display_name = "Custom Haskell";
      };
    };
    ...
  };
}

how about

{
  jupyterLib.mkKernels = {
    python = {
      # the env should be an individual python env
      env = pkgs.python3.withPackages [ ];
      # if env == {}, then env = pkgs.python3.withPackages (ps: ps withPackages) ++ [python.pkgs.ipykernel]);
      withPackages = [];
      override = {
        ...
      };
    };
    haskell = {
      # env = pkgs.haskellPackages.ghcWithPackages (p: with p; [ ihaskell ]);
      # if env == {}, then env = pkgs.haskellPackages.ghcWithPackages (p: with p; [ ihaskell ]) ++ ghcWithPackages p);
      ghcWithPackages = p: [ p.ihaskell ];
      override = {
        display_name = "Custom Haskell";
      };
    };
    ...
  };
}

In reply to @p14:matrix.org
g'day. I just started trying to use jupyter-notebook, but discovered that in nixos somewhere between nixpkgs/690e58e11de69953a1e76d0b9cc5f8caee63badd and present, keyboard navigation of cells in command mode is broken. (Up/down arrow, j/k should move up/down cells but nothing happens).

I've been trying to isolate the issue: if I take a recent nixpkgs commit and inject old jupyter-notebook, that breaks it, so it's not jupyter/notebook versions that's causing the breakage but presumably some other package or incompatibilities between them. Therefore I suspect this is not a jupyter bug but a nixpkgs bug. Any thoughts?

In reply to @gtrunsec:matrix.org
I don't mind rewriting a more powerful jupyenv as a new project, but I hope the current nixpkgs.jupyter can exist as much as possible as a library. If there's a plan for that project, then I would just need to focus on the integration of the data-science env and other Nix ecosystems

this sounds like a potentially larger scope than what i had in mind.

i thought we were just trying to solve the problem of "user wants to spin up Jupyterlab/notebook/console with some set of kernels." AFAICT this is roughly what jupyenv is for too. i gather you want to be able to do things like override the Python environment with one derived from poetry2nix. i think we can probably support this without too much trouble, just by making sure that the components that go into each kernel are easy to override.

if there's more to this then maybe a design doc is called for.