Overriding python with python3 in vim_configurable.customize

Question

I am following this template for configuring my custom vim with Nix. My vim-config/default.nix is as follows:

{ pkgs }:

let
  my_plugins = import ./plugins.nix { inherit (pkgs) vimUtils fetchFromGitHub; };
in with (pkgs // { python = pkgs.python3; }); vim_configurable.customize {
  name = "vim";
  vimrcConfig = {
    customRC = ''
      syntax on
      filetype on
      " ...
    '';

    vam.knownPlugins = vimPlugins // my_plugins;
    vam.pluginDictionaries = [
      { names = [
        "ctrlp"
        # ...
      ]; }
    ];
  };
}

Although there is a (pkgs // { python = pkgs.python3; }) override on line 5, python3 is still not used (when I run vim --version it shows +python -python3). Am I missing anything?

Answer 1

Since there are still people actively looking at this topic, I'll mention that there is an easier solution than the one I first came to:

my_vim_configurable = pkgs.vim_configurable.override {
    python = pkgs.python3;
};

My old answer:

It turns out that with (pkgs // { python = pkgs.python3; }); only modifies python in the scope following the with statement. The python used in vim_configurable is not affected. What I ended up doing is making a python3 version of vim_configurable using vimUtils.makeCustomizable:

vim-config/default.nix:

{ pkgs }:

let
  my_plugins = import ./plugins.nix { inherit (pkgs) vimUtils fetchFromGitHub; };
  configurable_nix_path = <nixpkgs/pkgs/applications/editors/vim/configurable.nix>;
  my_vim_configurable = with pkgs; vimUtils.makeCustomizable (callPackage configurable_nix_path {
    inherit (darwin.apple_sdk.frameworks) CoreServices Cocoa Foundation CoreData;
    inherit (darwin) libobjc cf-private;

    features = "huge"; # one of  tiny, small, normal, big or huge
    lua = pkgs.lua5_1;
    gui = config.vim.gui or "auto";
    python = python3;

    # optional features by flags
    flags = [ "python" "X11" ];
  });

in with pkgs; my_vim_configurable.customize {
  name = "vim";
  vimrcConfig = {
    customRC = ''
      syntax on
      “...
    '';

    vam.knownPlugins = vimPlugins // my_plugins;
    vam.pluginDictionaries = [
      { names = [
        "ctrlp"
        # ...
      ]; }
    ];
  };
}