Configuring Wezterm with Fennel

[fosskers]

Fennel is a language that compiles to Lua, and with a little bit of massaging can be used to configure Wezterm. Here is how I accomplished this.

In ~/.config/wezterm/wezterm.lua:

-- Workaround: https://github.com/wez/wezterm/issues/5323#issuecomment-2095316976
debug = {traceback = function() end}
local config = require("fennel").install().dofile("/home/colin/.config/wezterm/config.fnl")
return config

Note the workaround regarding debug.traceback.

Now, in ~/.config/wezterm/config.fnl:

(local wezterm (require :wezterm))
(local config (wezterm.config_builder))

;; --- Colours and Themes --- ;;
(set config.window_background_opacity 0.75)

;; --- Font --- ;;
(set config.font (wezterm.font "Source Code Pro"))
(set config.font_size 10)

;; Disable the Tab Bar
(set config.enable_tab_bar false)

config

For example. Now continue to configure things freely in Fennel as you wish.

Note about Lua locating fennel.lua

The fennel package provided by my distribution supplies fennel.lua at /usr/share/lua/5.4/fennel.lua, but apparently Lua/Wezterm only wants to look into /usr/local/share/.... I had to create a symlink in ~/.config/wezterm/ that points to the real location.

[jaidetree]

Awesome another fennel user! My config is at https://github.com/jaidetree/system/blob/fba37f4870577e39d5155cbaa122ee18bc160713/nix/home/wezterm.nix#L14-L24 with two distinctions:

local wezterm = require 'wezterm'
local configdir = wezterm.config_dir
local homedir = wezterm.home_dir

-- Fossker's version is better, but this is for nix users
fennel = dofile('${pkgs.lua54Packages.fennel}/share/lua/5.4/fennel.lua')

wezterm.log_error('Loaded fennel')

do
  local fnldir = (configdir .. "/fnl")
  for _, dir in ipairs({"/?.fnl", "/?/init.fnl"}) do
    fennel["path"] = (fnldir .. dir .. ";" .. fennel.path)
    fennel["macro-path"] = (fnldir .. dir .. ";" .. fennel["macro-path"])
  end
end

fennel.install()

_G['config-paths'] = {};
-- useful for nix users
_G['config-paths'].fish = '${pkgs.fish}/bin/fish';

local config = (require "j.wezterm.config")

return config

Modifying the paths lets you require modules as a root path, so if you want to split up your config into separate files, you can write something like the following:

(local some-module (require :j.config.wezterm.some-module))

Where j.config.wezterm would refer to ${XDG_CONFIG}/wezterm/fnl/j/config/wezterm/some-module.fnl.

The other is that it's geared towards nix users where the fennel path is in the nix store. Admittedly it's not very clean so open to alternatives if anyone has ideas.

[dragonmaus]

I took your config as a starting point and kind of ran with it, haha.

Here's what I came up with, more generalized for non-Nix users:

-- why these are not in the standard library escapes me…
string.split = function(str, sep)
    if sep == nil then
        sep = "%s"
    end

    local t = {}
    for s in str:gmatch(("([^" .. sep .. "]+)")) do
        table.insert(t, s)
    end

    return t
end

string.starts_with = function(str, sub)
    return (str:sub(1, #sub) == sub)
end

string.ends_with = function(str, sub)
    return ((sub == "") or (str:sub(-#sub) == sub))
end

local lua_to_fennel = function(path, macro)
    local ps = path:split(";")
    local new = {}

    -- duplicate each entry, replacing subfolders named "lua" with "fnl"
    -- and a trailing ".lua" with ".fnl"
    for _, p in ipairs(ps) do
        p = p:gsub("/lua/", "/fnl/")
        p = p:gsub("%.lua$", ".fnl")
        -- if generating macro-path, insert "/init-macros.fnl" before each "/init.fnl"
        if macro and p:ends_with("/init.fnl") then
            local q = p:gsub("/init%.fnl$", "/init-macros.fnl")
            table.insert(new, q)
        end
        table.insert(new, p)
    end

    -- re-add the original values to the end
    for _, p in ipairs(ps) do
        table.insert(new, p)
    end

    return table.concat(new, ";")
end

-- wezterm's embedded lua doesn't contain debug, which causes errors in fennel
debug = { traceback = function() end }

-- begin actual config file --

-- ensuring that fennel is in the search path is the responsibility of
-- the system and/or the user
local fennel = require("fennel")
local wezterm = require("wezterm")

local config_file = wezterm.config_file:gsub("%.lua$", ".fnl")

wezterm.add_to_config_reload_watch_list(config_file)

fennel.path = lua_to_fennel(package.path)
fennel.macroPath = lua_to_fennel(package.path, true)
-- make sure the fennel-style variable has the same value
fennel["macro-path"] = fennel.macroPath

return fennel.install().dofile(config_file)

(After further consideration, changed it to utilize the already-set 'package.path`.)