Haskell Language Server and Coc

Haskell has great IDE support via haskell-language-server (HLS).

Coc.nvim is the recommended extension to get Language Server Protocol (LSP) support for editing Haskell in neovim.

It turns out that home-manager has a module that, unlike the NixOS version, provides a declarative way to install and configure coc.nvim with Haskell support (EDIT: this is language-independent):

{
  programs.neovim = {
    coc = {
      enable = true;
      settings = {
        languageserver = {
          haskell = {
            command = "haskell-language-server-wrapper";
            args = [ "--lsp" ];
            rootPatterns = [
              "*.cabal"
              "cabal.project"
              "hie.yaml"
            ];
            filetypes = [ "haskell" "lhaskell" ];
          };
        };
      };
    };
  };
}

https://github.com/srid/nixos-config/commit/9a6410331063ae97ae405837559cf4c5b3990ada

It does work when trying out in the nix-shell of haskell-template.

Declarative plugin config in Nix

The above is neat—no need to hand-write VimScript or Lua just to configure the extension. Can we do the same for other neovim extensions in Nix? A couple of attempts exist: nix-neovim and NixVim.