@teto can you please describe how to use this module, perhaps some documentation in the manual and/or wiki?

@kalbasit right now I would say it just gives better error messages (typecheck) than plain nix errors when generating the vimrc.
I just updated the neovim to use it. You don't need to change anything.
The module can serve as documentation as to what parameters to pass to the neovim wrapper. The current vim configure attrset is confusing with nested sets, i.e., it's hard to configure vim without the wiki. I've seen seasoned nixos users fail to explain how to configure vim which shouldn't be the case.
Eventually I would like to get rid of configure's nested sets but right now I keep it for backwards compability and see if this can be merged first.

It seems like these kind of isolated modules don't appear in man configuration.nix, is there a way ? or that wouldn't make sense ? or generate man neovim.nix

another motivation is to be able to merge neovim configurations. I have a global neovim with minimal python haskell/environments and when I enter a project, I have a nix-shell that generates a neovim configuration adapted for that project (with the proper python3 environment).

@timokau any opinon ? I think this fits nix way better, like you can have a custom nvim(rc) for each nix-shell.
I haven't checked on channels:nixos-unstable but :UpdateRemotePlugins fails here for my user plugins, I can only get system ones registered. Is that the same on channels:nixos-unstable ? I can't remember.

I haven't looked at the implementation, but I don't really agree with the premise. Sorry if this sounds overly negative. That said I'm not trying to criticise you (you're doing good work) or block this from being merged, just giving my opinion.

NixOS modules have some advantages, but also significant disadvantages:

• harder to override
• harder to cherry-pick from a different release
• impossible to have multiple versions installed
• has to be re-implemented for user-level (like home-manager)

How does this enable you to have a custom nvimrc for each nix-shell? I'd argue its the other way around. You can have a custom nvim for each nix-shell right now, but I don't know how you would do that with a nixos module. It may simplify one use case (single neovim installation on nixos), but only adds to the confusion for all other use cases. In my humble opinion, nixos module should only be used for services and system configuration.

Also I think a lot of the complexity with the current way to configure neovim comes from vam and having multiple backends in general (#56338). If we only had native packages, it would significantly simplify the manual section and configuration is as easy as:

environment.systemPackages = with pkgs; [
  (neovim.override {
    configure = {
      packages.pkg = with vimPlugins; {
        start = [
          gruvbox
          base16-vim
        ];
        opt = [
          vim-nix
        ];
      };
      customRC = ''
        " something
      '';
    };
  })
]

I don't think that is particularly hard. Just unfortunately unstandardized and badly documented.

Regarding the other aspects of this PR:

Using -u to load the generated config breaks vim expectations about setting $MYVIMRC,
detecting and autoloading .nvimrc / .vimrc.
This PR changes the behavior (not backwards compatible) to fix this.

That would be nice to fix, but source doesn't set MYVIMRC either, does it? We could just set the MYVIMRC env var directly.

The configuration is not fully declarative anymore as it will also attempt to load the user configuration.

I think that is a net negative. At least as a default. It goes against the point of configuring it through nix.

It adds a knob to disable generation of the neovim remote plugin manisfest.

There shouldn't be any reason to do this. If there is, that is a bug that should be fixed. I'd be careful adding a config option to work around a bug. If it is broken right now, I'd rather have it disabled entirely until it is fixed.

Can anyone confirm that setting "MYVIMRC" to anything breaks module plugins?

I don't think that works as is but I merged some update from my main branch to reflect current changes.

@timokay thanks for the great feedback, I will adjust the PR once I finalize it to match the current determistic behavior. In this PR I use the nix system module rather than the nixos one, e.g., I pass a config (merged via the module system) when building neovim

For instance in my overlay I have:

   # this generates a config appropriate to work with the passed derivations
  # for instance to develop on a software from a nix-shell
  genNeovim = drvs: userConfig:
    with super;
    let
      requiredPythonModules = lib.debug.traceVal (super.python3Packages.requiredPythonModules drvs);

      # Here we generate a neovim config that allows to work with the passed 'drvs'
      # for instance adding the python propagatedBuildInputs if needed
      # or haskell ones if it's a haskell project etc.
      generatedConfig = {
        extraPython3Packages = compatFun (requiredPythonModules);
        # haskellPackages
        # TODO do the same for ruby / haskell
      };

      finalConfig = super.neovimConfig (
        super.lib.mkMerge [
          # project specific user config
          userConfig
          # my miniimal global config, when I am out of a nix-shell
          # the plugins/environments I always want available
          self.neovimDefaultConfig
          # a config generated from the input 'drvs' with an appropriate development
          # environment.
          generatedConfig
        ]
      );
    in
      wrapNeovim neovim-unwrapped-master (finalConfig);

and in my shell.nix for the python (in the future all languages) project I develop on, I have a my_neovim = genNeovim [ my_python_project] {} and it generates a neovim configuration with a python/haskell environment adapted to develop for this project.

Why do you need a nixos module for that? Couldn't you do the same thing with a base nvim and override?

Thank you for your contributions.
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current vim infra is still a pain for me, like some plugins do need custom configuration, we should make it possible to build vim configuration frameworks. For instance current unicode plugin should have at least:
let g:Unicode_data_directory='${final.vimPlugins.unicode-vim}/share/vim-plugins/unicode-vim/autoload/unicode' this line in config.

Also let me post https://envy.shados.net/ that may be too complex for nixpkgs but a source of possible inspiration

For what it's worth, you can get there without a nixos module: https://github.com/timokau/dotfiles/blob/c3340392081c126b5d1cf8cd3e7c519d1cdeb202/home/neovim.nix#L49

Which seems better to me since its more composable.

Thanks for the pointer, I am not saying you can't work around nixos, but nix is in good at handling dependencies and in this case it doesn't, for instance in my unicode example, either I wish installing unicode-vim would add let g:Unicode_data_directory to my customRC without my intervention (better than patching unicode-vim).

Couldn't that still be implemented as part of the configure mechanism instead of as a nixos module?

I marked this as stale due to inactivity. → More info

I still would like to leverage the nixpkgs module system to merge configurations but I am unlikely to do it soon. It's now easier to generate your own config via utilities in pkgs/applications/editors/neovim/utils.nix too. Thus closing for now.