Aspell with custom dictionaries configured

This quick post describes how to configure your aspell dictionaries. This might be needed for your development environment or it could be required for production systems to operate properly. One development need I have is to configure dictionaries for the aspell package for flyspell to work in my new emacs/spacemacs configuration (formerly my local vim configuration).

We can accomplish this in several ways:

• configure this at the system level
• configure this at the user level
• have our shell rc scripts set the ASPELL_CONF environment variable to the appropriate path for the dict-dir attribute.

On my development NixOS I chose to configure this in my user profile. If a production server required this I would chose the first approach (system level configuration) in my Nix expression for the system.

The rationale for the user level of Nix customization for development environments is because I like to reduce the scope of the system configuration on my laptops/tablets. I will typically only have one user account on these devices so I will not gain much by providing modern conveniences at the system-level, plus I can scp my user Nix expression to remote development environments to make my development experience portable, distributable, and reproducible with minimal effort.

User-level Nix Setup of aspell dictionaries

Since I care about the reproducibility of my development environment a great deal (hey, shit happens, even if the Universe has not killed my hard drive recently, I expect over time that will change) I have a user-level Nix expression under the path ${HOME}/.config/nixpkgs/config.nix. Nix/NixOS allows you to override/overlay your own configuration on top of the default nixpkgs/nixos channels in a variety of ways:

• using package overrides (old fashioned at this point given we have overlays)
• using overlays (introduced in 17.09, I think; relatively new)

Note: the user Nix expression used to be located/expected at ${HOME}/.nixpkgs/config.nix.

I am not going to share the entirety of my own user Nix expression inline here but my user Nix expression looks something like the following:

{ pkgs }:
let
  inherit (pkgs) aspellWithDicts; # among other inherits

  # setup custom vim and emacs/spacemacs configuration using Nix helpers already in nixpkgs

  # Now the custom aspell with custom dictionary set configured
  myaspell = aspellWithDicts (d: [d.en]);
  # Yes, I am a grotesque monolinguist, but you can put whatever dictionaries aspell offers in the list returned in the
  # lambda provided to `aspellWithDicts`.
in {
  allowUnfree = true;

  # some firefox and chromium attribute settings here that you probably don't care about, etc.

  # This is the old method of package overriding which I haven't yet converted to overlays, I know CURMUDGEON!
  packagesOverrides = pkgs: rec {
    myDevenv = buildEnv {
      name = "my-devenv";
      paths = with pkgs; [
        mtr
        tcpdump
        inetutils

        # lots of other things and then
        myaspell
      ];
    };
  };
}

Now let’s test this in our user environment/profile:

$ nix-env -i myaspell
... redacted spurious output not relevant to our testing ...

$ env | grep ASPELL
ASPELL_CONF=dict-dir /home/myusername/.nix-profile/lib/aspell

$ ls "$(readlink -f ~/.nix-profile/lib/aspell)/en_US*"
/nix/store/abcdef0123456789...-aspell-env/lib/aspell/en_US.multi
/nix/store/abcdef0123456789...-aspell-env/lib/aspell/en_US-variant_0.multi
...other entried redacted for space considerations
/nix/store/abcdef0123456789...-aspell-env/lib/aspell/en_US-wo_accents-only.rws

$ aspell list <<<"some words one of which will be mispelledk"
mispelledk

Overlays are recommended in recent versions of nixpkgs and above.

Cheers, until next time.