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CONTRIBUTING.md

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Contributing (and hacking onto) nixvim

This document is mainly for contributors to nixvim, but it can also be useful for extending nixvim.

Submitting a change

In order to submit a change you must be careful of several points:

  • The code must be properly formatted. This can be done through nix fmt.
  • The tests must pass. This can be done through nix flake check --all-systems (this also checks formatting).
  • The change should try to avoid breaking existing configurations.
  • If the change introduces a new feature it should add tests for it (see the architecture section for details).
  • The commit title should be consistent with our style. This usually looks like "plugins/: fixed some bug", you can browse the commit history of the files you're editing to see previous commit messages.

Nixvim Architecture

Nixvim is mainly built around pkgs.neovimUtils.makeNeovimConfig. This function takes a list of plugins (and a few other misc options), and generates a configuration for neovim. This can then be passed to pkgs.wrapNeovimUnstable to generate a derivation that bundles the plugins, extra programs and the lua configuration.

All the options that nixvim expose end up in those three places. This is done in the modules/output.nix file.

The guiding principle of nixvim is to only add to the init.lua what the user added to the configuration. This means that we must trim out all the options that were not set.

This is done by making most of the options of the type types.nullOr ...., and not setting any option that is null.

Plugin configurations

Most of nixvim is dedicated to wrapping neovim plugins such that we can configure them in Nix. To add a new plugin you need to do the following.

  1. Add a file in the correct sub-directory of plugins.
  • Most plugins should be added to plugins/by-name/<name>. Plugins in by-name are automatically imported 🚀
  • Occasionally, you may wish to add a plugin to a directory outside of by-name, such as plugins/colorschemes. If so, you will also need to add your plugin to plugins/default.nix to ensure it gets imported. Note: the imports list is sorted and grouped. In vim, you can usually use V (visual-line mode) with the :sort command to achieve the desired result.
  1. The vast majority of plugins fall into one of those two categories:
  • vim plugins: They are configured through global variables (g:plugin_foo_option in vimscript and vim.g.plugin_foo_option in lua).
    For those, you should use the lib.nixvim.vim-plugin.mkVimPlugin.
    -> See this plugin for an example.
  • neovim plugins: They are configured through a setup function (require('plugin').setup({opts})).
    For those, you should use the lib.nixvim.neovim-plugin.mkNeovimPlugin.
    -> See the template.
  1. Add the necessary parameters for the mkNeovimPlugin/mkVimPlugin:
  • name: The name of the plugin. The resulting nixvim module will have plugins.<name> as a path.
    For a plugin named foo-bar.nvim, set this to foo-bar (subject to exceptions).
  • originalName: The "real" name of the plugin (i.e. foo-bar.nvim). This is used mostly in documentation.
  • package: The nixpkgs package attr for this plugin e.g. "foo-bar-nvim for pkgs.vimPlugins.foo-bar-nvim, or [ "hello" "world" ] for pkgs.hello.world.
  • maintainers: Register yourself as a maintainer for this plugin:
  • settingsOptions: All or some (only the most important ones) option declarations for this plugin settings.
    See below for more information
  • settingsExample: An example of what could the settings attrs look like.

Declaring plugin options

Caution

Declaring settings-options is not required, because the settings option is a freeform type.

While settings options can be helpful for documentation and type-checking purposes, this is a double-edged sword because we have to ensure the options are correctly typed and documented to avoid unnecessary restrictions or confusion.

Tip

Learn more about the RFC 42 which motivated this new approach.

If you feel having nix options for some of the upstream plugin options adds value and is worth the maintenance cost, you can declare these in settingsOptions.

Take care to ensure option names exactly match the upstream plugin's option names (without globalsPrefix, if used). You must also ensure that the option type is permissive enough to avoid unnecessarily restricting config definitions. If unsure, you can forego declaring the option or use a permissive type such as lib.types.anything.

There are a number of helpers added into lib that can help you correctly implement them:

  • lib.nixvim.defaultNullOpts.{mkBool,mkInt,mkStr,...}: This family of helpers takes a default value and a description, and sets the Nix default to null. These are the main functions you should use to define options.
  • lib.nixvim.defaultNullOpts.<name>': These "prime" variants of the above helpers do the same thing, but expect a "structured" attrs argument. This allows more flexibility in what arguments are passed through to the underlying lib.mkOption call.
  • lib.types.rawLua: A type to represent raw lua code. The values are of the form { __raw = "<code>";}.

The resulting settings attrs will be directly translated to lua and will be forwarded the plugin:

  • Using globals (vim.g.<globalPrefix><option-name>) for plugins using mkVimPlugin
  • Using the require('<plugin>').setup(<options>) function for the plugins using mkNeovimPlugin

In either case, you don't need to bother implementing this part. It is done automatically.

Tests

Most of the tests of nixvim consist of creating a neovim derivation with the supplied nixvim configuration, and then try to execute neovim to check for any output. All output is considered to be an error.

The tests are located in the tests/test-sources directory, and should be added to a file in the same hierarchy than the repository. For example if a plugin is defined in ./plugins/ui/foo.nix the test should be added in ./tests/test-sources/ui/foo.nix.

Tests can either be a simple attribute set, or a function taking {pkgs} as an input. The keys of the set are configuration names, and the values are a nixvim configuration.

You can specify the special tests attribute in the configuration that will not be interpreted by nixvim, but only the test runner. The following keys are available:

  • tests.dontRun: avoid launching this test, simply build the configuration.

The tests are then runnable with nix flake check --all-systems.

There are a second set of tests, unit tests for nixvim itself, defined in tests/lib-tests.nix that use the pkgs.lib.runTests framework.

If you want to speed up tests, we have set up a Cachix for nixvim. This way, only tests whose dependencies have changed will be re-run, speeding things up considerably. To use it, just install cachix and run cachix use nix-community.