**:warning: :warning: :warning: A more up-to-date version of this guide is available in the Neovim documentation, see [`:help lua-guide`](https://neovim.io/doc/user/lua-guide.html#lua-guide) :warning: :warning: :warning:**
The [integration of Lua](https://www.youtube.com/watch?v=IP3J56sKtn0) as a [first-class language inside Neovim](https://github.com/neovim/neovim/wiki/FAQ#why-embed-lua-instead-of-x) is shaping up to be one of its life-giving 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.
- The [Learn X in Y minutes page about Lua](https://learnxinyminutes.com/docs/lua/) should give you a quick overview of the basics
- [This guide](https://github.com/medwatt/Notes/blob/main/Lua/Lua_Quick_Guide.ipynb) is also a good resource for getting started quickly
- If videos are more to your liking, Derek Banas has a [1-hour tutorial on the language](https://www.youtube.com/watch?v=iMacxZQMPXs)
- Want something a little more interactive with runnable examples? Try [the LuaScript tutorial](https://www.luascript.dev/learn)
- The [lua-users wiki](http://lua-users.org/wiki/LuaDirectory) is full of useful information on all kinds of Lua-related topics
- The [official reference manual for Lua](https://www.lua.org/manual/5.1/) should give you the most comprehensive tour of the language (exists as a Vimdoc plugin if you want to read it from the comfort of your editor: [milisims/nvim-luaref](https://github.com/milisims/nvim-luaref))
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](https://staff.fnwi.uva.nl/h.vandermeer/docs/lua/luajit/luajit_intro.html) 2.1.0, which maintains compatibility with Lua 5.1.
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.
Note: `init.lua` is of course _completely_ optional. Support for `init.vim` is not going away and is still a valid option for configuration. Do keep in mind that some features are not 100% exposed to Lua yet.
Lua modules are 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). You can `require()` files in this folder as Lua modules.
Much like Vimscript files, Lua files can be loaded automatically from special folders in your `runtimepath`. Currently, the following folders are supported:
Note: each `:lua` command has its own scope and variables declared with the `local` keyword are not accessible outside of the command. This won't work:
Note 2: the `print()` function in Lua behaves similarly to the `:echomsg` command. Its output is saved in the message-history and can be suppressed by the `:silent` command.
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 `return`ed from the chunk is used to determine what each line should be replaced with.
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:
`:runtime` is a little different: it uses the `'runtimepath'` option to determine which files to source. See [`:help :runtime`](https://neovim.io/doc/user/repeat.html#:runtime) for more details.
You might be wondering what the difference between calling the `require()` function and sourcing a Lua file is and whether you should prefer one way over the other. They have different use cases:
- is a built-in Lua function. It allows you to take advantage of Lua's module system
- searches for modules in `lua/` folders in your `'runtimepath'`
- keeps track of what modules have been loaded and prevents a script from being parsed and executed a second time. If you change the file containing the code for a module and try to `require()` it a second time while Neovim is running, the module will not actually update
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).
`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`:
This global Vim variable allows you to call Lua functions in the global namespace ([`_G`](https://www.lua.org/manual/5.1/manual.html#pdf-_G)) directly from Vimscript. Again, Vim data types are converted to Lua types and vice versa.
You can get Lua syntax highlighting inside .vim files by putting `let g:vimsyn_embed = 'l'` in your configuration file. See [`:help g:vimsyn_embed`](https://neovim.io/doc/user/syntax.html#g:vimsyn_embed) for more on this option.
Neovim exposes a global `vim` variable which serves as an entry point to interact with its APIs from Lua. It provides users with an extended "standard library" of functions as well as various sub-modules.
This list is by no means comprehensive. If you wish to know more about what's made available by the `vim` variable, [`:help lua-stdlib`](https://neovim.io/doc/user/lua.html#lua-stdlib) and [`:help lua-vim`](https://neovim.io/doc/user/lua.html#lua-vim) are the way to go. Alternatively, you can do `:lua print(vim.inspect(vim))` to get a list of every module. API functions are documented under [`:help api-global`](https://neovim.io/doc/user/api.html#api-global).
Writing `print(vim.inspect(x))` every time you want to inspect the contents of an object can get pretty tedious. It might be worthwhile to have a global wrapper function somewhere in your configuration (in Neovim 0.7.0+, this function is built-in, see [`:help vim.pretty_print()`](https://neovim.io/doc/user/lua.html#vim.pretty_print())):
Additionally, you may find that built-in Lua functions are sometimes lacking compared to what you would find in other languages (for example `os.clock()` only returns a value in seconds, not milliseconds). Be sure to look at the Neovim stdlib (and `vim.fn`, more on that later), it probably has what you're looking for.
This function evaluates a Vimscript expression string and returns its value. Vimscript data types are automatically converted to Lua types (and vice versa).
This function evaluates a chunk of Vimscript code. It takes in a string containing the source code to execute and a boolean to determine whether the output of the code should be returned by the function (you can then store the output in a variable, for example).
Being able to escape keycodes is actually a Vimscript feature. Aside from the usual escape sequences like `\r`, `\42` or `\x10` that are common to many programming languages, Vimscript `expr-quotes` (strings surrounded with double quotes) allow you to escape the human-readable representation of Vim keycodes.
A few meta-accessors are available if you want to set options in a more "idiomatic" way. They essentially wrap the above API functions and allow you to manipulate options as if they were variables:
These wrappers also have more sophisticated `vim.opt*` variants that provide convenient mechanisms for setting options in Lua. They're similar to what you might be used to in your `init.vim`:
Wrappers for list-like, map-like and set-like options also come with methods and metamethods that work similarly to their `:set+=`, `:set^=` and `:set-=` counterparts in Vimscript.
With the exception of predefined Vim variables, they can also be deleted (the `:unlet` command is the equivalent in Vimscript). Local variables (`l:`), script variables (`s:`) and function arguments (`a:`) cannot be manipulated as they only make sense in the context of a Vim script, Lua has its own scoping rules.
If you are unfamiliar with what these variables do, [`:help internal-variables`](https://neovim.io/doc/user/eval.html#internal-variables) describes them in detail.
Variables that are scoped to a buffer, a window or a tabpage also receive a number (using `0` will set/get/delete the variable for the current buffer/window/tabpage):
Some variable names may contain characters that cannot be used for identifiers in Lua. You can still manipulate these variables by using this syntax: `vim.g['my#variable']`.
You cannot add/update/delete keys from a dictionary stored in one of these variables. For example, this snippet of Vimscript code does not work as expected:
It is distinct from `vim.api.nvim_call_function` in that converting Vim/Lua objects is automatic: `vim.api.nvim_call_function` returns a table for floating point numbers and does not accept Lua closures while `vim.fn` handles these types transparently.
Neovim has an extensive library of powerful built-in functions that are very useful for plugins. See [`:help vim-function`](https://neovim.io/doc/user/eval.html#vim-function) for an alphabetical list and [`:help function-list`](https://neovim.io/doc/user/usr_41.html#function-list) for a list of functions grouped by topic.
Some Vim functions that should return a boolean return `1` or `0` instead. This isn't a problem in Vimscript as `1` is truthy and `0` falsy, enabling constructs like these:
In Lua however, only `false` and `nil` are considered falsy, numbers always evaluate to `true` no matter their value. You have to explicitly check for `1` or `0`:
The second argument is a string containing the left-hand side of the mapping (the key or set of keys that trigger the command defined in the mapping). An empty string is equivalent to `<Nop>`, which disables a key.
The final argument is a table containing boolean options for the mapping as defined in [`:help :map-arguments`](https://neovim.io/doc/user/map.html#:map-arguments) (including `noremap` and excluding `buffer`). Since Neovim 0.7.0, you can also pass a `callback` option to invoke a Lua function instead of the right-hand side when executing the mapping.
`vim.api.nvim_get_keymap()` takes a string containing the shortname of the mode for which you want the list of mappings (see table above). The return value is a table containing all global mappings for the mode.
The fourth (optional) argument is a table of options that correspond to the options passed to `vim.api.nvim_set_keymap()`, with a few additions (see [`:help vim.keymap.set()`](https://neovim.io/doc/user/lua.html#vim.keymap.set()) for the full list).
Defining keymaps with a Lua function is different from using a string. The usual way to show information about a keymap like `:nmap <Leader>ex1` will not output useful information (the string itself), but instead only show `Lua function`. It is recommended to add a `desc` key to describe the behavior of your keymap. This is especially important for documenting plugin mappings so users can understand the usage of the keymap more easily.
An interesting feature of this API is that it irons out some historical quirks of Vim mappings:
- Mappings are `noremap` by default, except when the `rhs` is a `<Plug>` mapping. This means you rarely have to think about whether a mapping should be recursive or not:
A string (in which case it will be executed as Vimscript). You can use escape sequences like `<q-args>`, `<range>`, etc. like you would with `:command`
Or a Lua function. It receives a dictionary-like table that contains the data normally provided by escape sequences (see [`:help nvim_create_user_command()`](https://neovim.io/doc/user/api.html#nvim_create_user_command()) for a list of available keys)
The third argument lets you pass command attributes as a table (see [`:help command-attributes`](https://neovim.io/doc/user/map.html#command-attributes)). Since you can already define buffer-local user commands with `vim.api.nvim_buf_create_user_command()`, `-buffer` is not a valid attribute.
-`desc` allows you to control what gets displayed when you run `:command {cmd}` on a command defined as a Lua callback. Similarly to keymaps, it is recommended to add a `desc` key to commands defined as Lua functions.
-`force` is equivalent to calling `:command!` and replaces a command if one with the same name already exists. It is true by default, unlike its Vimscript equivalent.
The `-complete` attribute can take a Lua function in addition to the attributes listed in [`:help :command-complete`](https://neovim.io/doc/user/map.html#:command-complete).
Buffer-local user commands also take a buffer number as their first argument. This is an advantage over `-buffer` which can only define a command for the current buffer.
The `-complete=custom` attribute automatically filters completion candidates and has built-in wildcard ([`:help wildcard`](https://neovim.io/doc/user/editing.html#wildcard)) support:
In Lua, the `require()` function caches modules. This is a good thing for performance, but it can make working on plugins a bit cumbersome because modules are not updated on subsequent `require()` calls.
The [nvim-lua/plenary.nvim](https://github.com/nvim-lua/plenary.nvim) plugin has a [custom function](https://github.com/nvim-lua/plenary.nvim/blob/master/lua/plenary/reload.lua) that does this for you.
When using double bracketed strings, resist the temptation to pad them! While it is fine to do in contexts where spaces are ignored, it can cause hard to debug issues when whitespace is significant:
A common pattern in Vim scripts is to use `1` or `0` instead of proper booleans. Indeed, Vim did not have a separate boolean type until version 7.4.1154.
If you're using linters and/or language servers to get diagnostics and autocompletion for Lua projects, you may have to configure Neovim-specific settings for them. Here are a few recommended settings for popular tools:
You can get [luacheck](https://github.com/mpeterv/luacheck/) to recognize the `vim` global by putting this configuration in `~/.luacheckrc` (or `$XDG_CONFIG_HOME/luacheck/.luacheckrc`):
The [nvim-lspconfig](https://github.com/neovim/nvim-lspconfig/) repository contains [instructions to configure sumneko/lua-language-server](https://github.com/neovim/nvim-lspconfig/blob/master/doc/server_configurations.md#sumneko_lua) (the example uses the built-in LSP client but the configuration should be identical for other LSP client implementations).
For more information on how to configure [sumneko/lua-language-server](https://github.com/sumneko/lua-language-server/) see ["Setting"](https://github.com/sumneko/lua-language-server/wiki/Setting)
The [rafcamlet/coc-nvim-lua](https://github.com/rafcamlet/coc-nvim-lua/) completion source for [coc.nvim](https://github.com/neoclide/coc.nvim/) provides completion items for the Neovim stdlib.
You can debug Lua code running in a separate Neovim instance with [jbyuki/one-small-step-for-vimkind](https://github.com/jbyuki/one-small-step-for-vimkind)
The plugin uses the [Debug Adapter Protocol](https://microsoft.github.io/debug-adapter-protocol/). Connecting to a debug adapter requires a DAP client like [mfussenegger/nvim-dap](https://github.com/mfussenegger/nvim-dap/) or [puremourning/vimspector](https://github.com/puremourning/vimspector/).
[wbthomason/packer.nvim](https://github.com/wbthomason/packer.nvim) supports Luarocks packages. Instructions for how to set this up are available in the [README](https://github.com/wbthomason/packer.nvim/#luarocks-support)
`vim.lsp` is the module that controls the built-in LSP client. The [neovim/nvim-lspconfig](https://github.com/neovim/nvim-lspconfig/) repository contains default configurations for popular language servers.
`vim.treesitter` is the module that controls the integration of the [Tree-sitter](https://tree-sitter.github.io/tree-sitter/) library in Neovim. If you want to know more about Tree-sitter, you may be interested in this [presentation (38:37)](https://www.youtube.com/watch?v=Jes3bD6P0To).
Probably one of the most well-known transpilers for Lua. Adds a lots of convenient features like classes, list comprehensions or function literals. The [svermeulen/nvim-moonmaker](https://github.com/svermeulen/nvim-moonmaker) plugin allows you to write Neovim plugins and configuration directly in Moonscript.
A lisp that compiles to Lua. You can write configuration and plugins for Neovim in Fennel with the [Olical/aniseed](https://github.com/Olical/aniseed) or the [Hotpot](https://github.com/rktjmp/hotpot.nvim) plugin. Additionally, the [Olical/conjure](https://github.com/Olical/conjure) plugin provides an interactive development environment that supports Fennel (among other languages).
The name Teal comes from pronouncing TL (typed lua). This is exactly what it tries to do - add strong typing to lua while otherwise remaining close to standard lua syntax. The [nvim-teal-maker](https://github.com/svermeulen/nvim-teal-maker) plugin can be used to write Neovim plugins or configuration files directly in Teal