Fennel is a small lisp-like language that compiles to Lua. I have become very interested in lisp and lisp-like languages, the syntax is simple and has great potential for elegance. Since Neovim is configured with Lua, we can use Fennel to write Neovim config with a lisp syntax!
Getting Started
Since Fennel is not officially supported, I am using nfnl to seamlessly integrate fennel with my config files. The setup here is very quick and easy. Just create a new file named .nfnl.fnl in your configuration directory and install "Olical/nfnl" using your plugin manager. From here any Fennel file you create under your configuration directory will be compiled to Lua for use by Neovim.
Translating a Lazy Plugin
Since I am using Lazy I have my plugins separated into modules under /lua/plugins/*.lua. I'll use one of these as an example for Fennel's syntax.
return { 'rose-pine/neovim' , name = 'rose-pine' , lazy = false , priority = 1000 , dependencies = { 'f-person/auto-dark-mode.nvim' , } , config = function () require ( "rose-pine" ). setup ( { dark_variant = "moon" } ) local auto_dark_mode = require ( 'auto-dark-mode' ) auto_dark_mode . setup ( { update_interval = 1000 , set_dark_mode = function () vim . api . nvim_set_option ( 'background' , 'dark' ) vim . cmd ( 'colorscheme rose-pine' ) end , set_light_mode = function () vim . api . nvim_set_option ( 'background' , 'light' ) vim . cmd ( 'colorscheme rose-pine' ) end , } ) auto_dark_mode . init () end } This is my module for theming, it includes a small configuration function for automatically switching themes when my system preference changes. With some quick refactoring the Fennel equivalent looks like this:
{ 1 :rose-pine/neovim :name "rose-pine" :lazy false :priority 1000 :dependencies [:f-person/auto-dark-mode.nvim] :config (fn [] (let [rose-pine (require :rose-pine)] (rose-pine.setup { :dark_variant "moon" })) (let [auto-dark-mode (require :auto-dark-mode)] (auto-dark-mode.setup { :update_interval 1000 :set_dark_mode (fn [] (vim.api.nvim_set_option "background" "dark" ) (vim.cmd "colorscheme rose-pine" ) ) :set_light_mode (fn [] (vim.api.nvim_set_option "background" "light" ) (vim.cmd "colorscheme rose-pine" ) ) }) (auto-dark-mode.init) ) )}With this example there are a few syntax differences that I enjoy.
First is Fennel's key/value syntax for tables. You declare pairs with :key-name followed by a value. This works out great, except when you mix named and unnamed values. In the above you may wonder why 1 appears. This is because the first entry is indexed with no key name. If there is a way to mitigate these numbered keys I'd love to know.
Following with key/value pairs, Fennel has a separate table syntax for sequential tables: []. These are similar to arrays, in this example :dependencies has a sequential table for a value containing 1 string f-person/auto-dark-mode.nvim.
I am still early in my lisp and Fennel adventure, but so far it has been great! Once my configuration is fully Fenneled out I look forward to sitting with it and molding the code to fit Fennel's style better.