Include expressions for all dependencies of a package

[syedmoizurrehman]

When generating a nix expression for a Python package whose dependencies are not available in nixpkgs, I need to run nix-init for each of the missing dependency and then combine the nix expressions manually in a single nix expression to be able to build the package.

Is there a way to have nix-init recursively invoke itself on all dependencies and generate a single nix expression for the entire package?

For example, running nix-init for pydoc-markdown with buildPythonPackage will generate a nix expression for pydoc-markdown and its dependencies.

$ nix-init -u https://pypi.org/project/pydoc-markdown

{
  lib,
  buildPythonPackage,
  fetchPypi,
  poetry-core,
  click,
  databind-core,
  databind-json,
  docspec,
  docspec-python,
  docstring-parser,
  jinja2,
  nr-util,
  pyyaml,
  requests,
  tomli,
  tomli-w,
  watchdog,
  yapf,
}:

buildPythonPackage rec {
  pname = "pydoc-markdown";
  version = "4.8.2";
  pyproject = true;

  src = fetchPypi {
    ...
  };

  build-system = [
    poetry-core
  ];

  dependencies = [
    click
    databind-core
    databind-json
    docspec
    docspec-python
    docstring-parser
    jinja2
    nr-util
    pyyaml
    requests
    tomli
    tomli-w
    watchdog
    yapf
  ];

  pythonImportsCheck = [
    "pydoc_markdown"
  ];

  meta = {
    ...
  };
}

This expression requires the dependencies as arguments but some packages (such as databind-core) are not available in nixpkgs.

Once the feature is implemented, the generated expression will include the nix expression for all the dependencies such as following:

{
  lib,
  buildPythonPackage,
  fetchPypi,
  poetry-core,
}:

buildPythonPackage rec {
  pname = "pydoc-markdown";
  version = "4.8.2";
  pyproject = true;

  click = buildPythonPackage rec { ... };
  databind-core = buildPythonPackage rec { ... };
  databind-json = buildPythonPackage rec { ... };
  docspec = buildPythonPackage rec { ... };
  docspec-python = buildPythonPackage rec { ... };
  docstring-parser = buildPythonPackage rec { ... };
  jinja2 = buildPythonPackage rec { ... };
  nr-util = buildPythonPackage rec { ... };
  pyyaml = buildPythonPackage rec { ... };
  requests = buildPythonPackage rec { ... };
  tomli = buildPythonPackage rec { ... };
  tomli-w = buildPythonPackage rec { ... };
  watchdog = buildPythonPackage rec { ... };
  yapf = buildPythonPackage rec { ... };

  src = fetchPypi {
    ...
  };

  build-system = [
    poetry-core
  ];

  dependencies = [
    click
    databind-core
    databind-json
    docspec
    docspec-python
    docstring-parser
    jinja2
    nr-util
    pyyaml
    requests
    tomli
    tomli-w
    watchdog
    yapf
  ];

  pythonImportsCheck = [
    "pydoc_markdown"
  ];

  meta = {
    ...
  };
}

This behavior would be turned off by default. Passing a flag (such as -r for recursive) to nix-init would enable it.

If this or an equivalent feature is already available, please let me know how I can use it.

Thanks.

[figsoda]

This would be particularly useful with python, though I'm not sure if there is a good way for nix-init itself to do this that is suitable for nixpkgs contributions until NixOS/nixpkgs#393981 is resolved (NixOS/nixpkgs#449896 seems pretty promising). Trying to touch top-level/python-packages.nix seems like a bad idea, and inlining the dependencies like that wouldn't be suitable for contributing to nixpkgs, which is the primary goal of nix-init.

Hacking up a script using headless mode (#665) and by parsing Nix error messages might do the trick for now.