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README.md
Getting started using Lua in Neovim
Introduction
The integration of Lua as a first-class language inside Neovim is shaping up to be one of its killer features. However, the amount of teaching material for learning how to write plugins in Lua is not as large as what you would find for writing them in Vimscript. This is an attempt at providing some basic information to get people started.
This guide assumes you are using the latest nightly build of Neovim. Since version 0.5 of Neovim is a development version, keep in mind that some APIs that are being actively worked on are not quite stable and might change before release.
Learning Lua
If you are not already familiar with the language, there are plenty of resources to get started:
- The Learn X in Y minutes page about Lua should give you a quick overview of the basics
- If videos are more to your liking, Derek Banas has a 1-hour tutorial on the language
- The lua-users wiki is full of useful information on all kinds of Lua-related topics
- The official reference manual for Lua should give you the most comprehensive tour of the language
It should also be noted that Lua is a very clean and simple language. It is easy to learn, especially if you have experience with similar scripting languages like JavaScript. You may already know more Lua than you realise!
Note: the version of Lua that Neovim embeds is LuaJIT 2.1.0, which maintains compatibility with Lua 5.1 (with a few 5.2 extensions)
Existing tutorials for writing Lua in Neovim
A few tutorials have already been written to help people write plugins in Lua. Some of them helped quite a bit when writing this guide. Many thanks to their authors.
- teukka.tech - From init.vim to init.lua
- 2n.pl - How to write neovim plugins in Lua
- 2n.pl - How to make UI for neovim plugins in Lua
- ms-jpq - Neovim Async Tutorial
Where to put Lua files
Lua files are typically found inside a lua/ folder in your runtimepath (for most users, this will mean ~/.config/nvim/lua on *nix systems and ~/AppData/Local/nvim/lua on Windows). The package.path and package.cpath globals are automatically adjusted to include lua files in this folder. This means you can require() these files as Lua modules.
Let's take the following folder structure as an example:
📂 ~/.config/nvim
├── 📁 after
├── 📁 ftplugin
├── 📂 lua
│ ├── 🌑 myluamodule.lua
│ └── 📂 other_modules
│ ├── 🌑 anothermodule.lua
│ └── 🌑 init.lua
├── 📁 pack
├── 📁 plugin
├── 📁 syntax
└── 🇻 init.vim
The following Lua code will load myluamodule.lua:
require('myluamodule')
Notice the absence of a .lua extension.
Similarly, loading other_modules/anothermodule.lua is done like so:
require('other_modules.anothermodule')
-- or
require('other_modules/anothermodule')
Path separators are denoted by either a dot . or a slash /.
A folder containing an init.lua file can be required directly, without have to specify the name of the file.
require('other_modules') -- loads other_modules/init.lua
For more information: :help lua-require
Unlike .vim files, .lua files are not automatically sourced from directories in your runtimepath. Instead, you have to source/require them from Vimscript. There are plans to add the option to load an init.lua file as an alternative to init.vim:
Using Lua from Vimscript
:lua
This command executes a chunk of lua code.
:lua require('myluamodule')
Multi-line scripts are possible using heredoc syntax:
echo "Here's a bigger chunk of Lua code"
lua << EOF
local mod = require('mymodule')
local tbl = {1, 2, 3}
for k, v in ipairs(tbl) do
mod.method(v)
end
print(tbl)
EOF
See also:
:help :lua:help :lua-heredoc
Caveats
You don't get correct syntax highlighting when writing Lua in a .vim file. It might be more convenient to use the :lua command as an entry point for requiring external lua files.
:luado
This command executes a chunk of lua code that acts on a range of lines in the current buffer. If no range is specified, the whole buffer is used instead. Whatever string is returned from the chunk is used to determine what each line should be replaced with.
The following command would replace every line in the current buffer with the text hello world:
:luado return 'hello world'
Two implicit line and linenr variables are also provided. line is the text of the line being iterated upon whereas linenr is its number. The following command would make every line whose number is divisible by 2 uppercase:
:luado if linenr % 2 == 0 then return line:upper() end
See also:
:help :luado
:luafile
This command sources a lua file.
:luafile ~/foo/bar/baz/myluafile.lua
It is analogous to the :source command for .vim files or the built-in dofile() function in Lua.
See also:
:help :luafile
luaeval()
This built-in Vimscript function evaluates a Lua expression string and returns its value. Lua data types are automatically converted to Vimscript types (and vice versa).
" You can store the result in a variable
let variable = luaeval('1 + 1')
echo variable
" 2
let concat = luaeval('"Lua".." is ".."awesome"')
echo concat
" 'Lua is awesome'
" List-like tables are converted to Vim lists
let list = luaeval('{1, 2, 3, 4}')
echo list[0]
" 1
echo list[1]
" 2
" Note that unlike Lua tables, Vim lists are 0-indexed
" Dict-like tables are converted to Vim dictionaries
let dict = luaeval('{foo = "bar", baz = "qux"}')
echo dict.foo
" 'bar'
" Same thing for booleans and nil
echo luaeval('true')
" v:true
echo luaeval('nil')
" v:null
" You can create Vimscript aliases for Lua functions
let LuaMathPow = luaeval('math.pow')
echo LuaMathPow(2, 2)
" 4
let LuaModuleFunction = luaeval('require("mymodule").myfunction')
call LuaModuleFunction()
luaeval() takes an optional second argument that allows you to pass data to the expression. You can then access that data from Lua using the magic global _A:
echo luaeval('_A[1] + _A[2]', [1, 1])
" 2
echo luaeval('string.format("Lua is %s", _A)', 'awesome')
" 'Lua is awesome'
See also:
:help luaeval()