How to add extra tree-sitter grammars

[akirak]

If you want to enable tree-sitter grammars that are not shipped with Emacs, you can add them with a setting like this:

initFiles =
  [
    ./init.el
    (
      pkgs.writeText "init-treesit.el" ''
        (add-to-list 'treesit-extra-load-path "${
          pkgs.linkFarm "treesit-grammars"
          (
            map (drv: {
              name = "lib${
                pkgs.lib.removeSuffix "-grammar" (pkgs.lib.getName drv)
              }${
                pkgs.stdenv.targetPlatform.extensions.sharedLibrary
              }";
              path = "${drv}/parser";
            })
            [
              pkgs.tree-sitter-grammars.tree-sitter-eex
              pkgs.tree-sitter-grammars.tree-sitter-heex
              pkgs.tree-sitter-grammars.tree-sitter-elixir
            ]
          )
        }/")
      ''
    )
  ];

The code is based on https://github.com/DamienCassou/nixpkgs/blob/8f0515dbf74c886b61639ccad5a1ea7c2f51265d/pkgs/applications/editors/emacs/elisp-packages/manual-packages/treesit-grammars/default.nix.

It might be possible to add an extra support for tree-sitter grammars to twist.nix to make the configuration concise. For now, the above method works.

[akirak]

Now #165 is a recommended solution.