*nvim-lua-guide.txt* Getting started using Lua in Neovim ============================================================================== INTRODUCTION *luaguide-introduction* 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 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 at least version 0.5 of Neovim. 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: 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: wsdjeg/luarefvim: https://github.com/wsdjeg/luarefvim 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. 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: https://teukka.tech/luanvim.html - dev.to - How to write neovim plugins in Lua: https://dev.to/2nit/how-to-write-neovim-plugins-in-lua-5cca - dev.to - How to make UI for neovim plugins in Lua: https://dev.to/2nit/how-to-make-ui-for-neovim-plugins-in-lua-3b6e - ms-jpq - Neovim Async Tutorial: https://github.com/ms-jpq/neovim-async-tutorial - oroques.dev - Neovim 0.5 features and the switch to init.lua: https://oroques.dev/notes/neovim-init/ - Building A Vim Statusline from Scratch - jdhao's blog: https://jdhao.github.io/2019/11/03/vim_custom_statusline/ - Configuring Neovim using Lua: https://icyphox.sh/blog/nvim-lua/ - Devlog | Everything you need to know to configure neovim using lua: https://vonheikemen.github.io/devlog/tools/configuring-neovim-using-lua/ Companion plugins~ - Vimpeccable: https://github.com/svermeulen/vimpeccable - Plugin to help write your .vimrc in Lua - plenary.nvim: https://github.com/nvim-lua/plenary.nvim - All the lua functions I don't want to write twice - popup.nvim: https://github.com/nvim-lua/popup.nvim - An implementation of the Popup API from vim in Neovim - nvim_utils: https://github.com/norcalli/nvim_utils - nvim-luadev: https://github.com/bfredl/nvim-luadev - REPL/debug console for nvim lua plugins - nvim-luapad: https://github.com/rafcamlet/nvim-luapad - Interactive real time neovim scratchpad for embedded lua engine - nlua.nvim: https://github.com/tjdevries/nlua.nvim - Lua Development for Neovim - BetterLua.vim: https://github.com/euclidianAce/BetterLua.vim - Better Lua syntax highlighting in Vim/NeoVim ============================================================================== WHERE TO PUT LUA FILES *luaguide-where-to-put-lua-files* init.lua~ Neovim supports loading an `init.lua` file for configuration instead of the usual `init.vim`. 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. See also: - |config| Modules~ 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. 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 having to specify the name of the file. > require('other_modules') -- loads other_modules/init.lua < Requiring a nonexistent module or a module which contains syntax errors aborts the currently executing script. `pcall()` may be used to prevent errors. > local ok, _ = pcall(require, 'module_with_error') if not ok then -- not loaded end < See also: - |lua-require| Tips~ Several Lua plugins might have identical filenames in their `lua/` folder. This could lead to namespace clashes. If two different plugins have a `lua/main.lua` file, then doing `require('main')` is ambiguous: which file do we want to source? It might be a good idea to namespace your config or your plugin with a top-level folder, like so: `lua/plugin_name/main.lua` Runtime files~ Much like Vimscript files, Lua files can be loaded automatically from special folders in your `runtimepath`. Currently, the following folders are supported: - `colors/` - `compiler/` - `ftplugin/` - `ftdetect/` - `indent/` - `plugin/` - `syntax/` Note: in a runtime directory, all `*.vim` files are sourced before `*.lua` files. See also: - |'runtimepath'| - |load-plugins| Tips~ Since runtime files aren't based on the Lua module system, two plugins can have a `plugin/main.lua` file without it being an issue. ============================================================================== USING LUA FROM VIMSCRIPT *luaguide-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 < 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: > :lua local foo = 1 :lua print(foo) " prints 'nil' instead of '1' < 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. See also: - |:lua| - |:lua-heredoc| :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 `return`ed 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: - |:luado| Sourcing Lua files~ Neovim provides 3 Ex commands to source Lua files - `:luafile` - `:source` - `:runtime` `:luafile` and `:source` are very similar: > :luafile ~/foo/bar/baz/myluafile.lua :luafile % :source ~/foo/bar/baz/myluafile.lua :source % < `:source` also supports ranges, which can be useful to only execute part of a script: > :1,10source < `:runtime` is a little different: it uses the `'runtimepath'` option to determine which files to source. See |:runtime| for more details. See also: - |:luafile| - |:source| - |:runtime| Sourcing a lua file vs calling require():~ 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: - `require()`: - 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 - `:luafile`, `:source` and `:runtime`: - are Ex commands. They do not support modules - execute the contents of a script regardless of whether it has been executed before - `:luafile` and `:source` take a path that is either absolute or relative to the working directory of the current window - `:runtime` uses the `'runtimepath'` option to find files Files sourced via `:source`, `:runtime` or automatically from runtime directories will also show up in `:scriptnames` and `--startuptime` 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() " It is also possible to pass Lua functions as values to Vim functions lua X = function(k, v) return string.format("%s:%s", k, v) end echo map([1, 2, 3], luaeval("X")) < `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: - |luaeval()| v:lua~ 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. > call v:lua.print('Hello from Lua!') " 'Hello from Lua!' let scream = v:lua.string.rep('A', 10) echo scream " 'AAAAAAAAAA' " How about a nice statusline? lua << EOF function _G.statusline() local filepath = '%f' local align_section = '%=' local percentage_through_file = '%p%%' return string.format( '%s%s%s', filepath, align_section, percentage_through_file ) end EOF set statusline=%!v:lua.statusline() " Also works in expression mappings lua << EOF function _G.check_back_space() local col = vim.api.nvim_win_get_cursor(0)[2] return (col == 0 or vim.api.nvim_get_current_line():sub(col, col):match('%s')) and true end EOF inoremap \ pumvisible() ? "\" : \ v:lua.check_back_space() ? "\" : \ completion#trigger_completion() < See also: - |v:lua| - |v:lua-call| Caveats~ This variable can only be used to call functions. The following will always throw an error: > " Aliasing functions doesn't work let LuaPrint = v:lua.print " Accessing dictionaries doesn't work echo v:lua.some_global_dict['key'] " Using a function as a value doesn't work echo map([1, 2, 3], v:lua.global_callback) < Tips~ You can get Lua syntax highlighting inside .vim files by putting `let g:vimsyn_embed = 'l'` in your configuration file. See |g:vimsyn_embed| for more on this option. ============================================================================== THE VIM NAMESPACE *luaguide-the-vim-namespace* 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. Some notable functions and modules include: - `vim.inspect`: pretty-print Lua objects (useful for inspecting tables) - `vim.regex`: use Vim regexes from Lua - `vim.api`: module that exposes API functions (the same API used by remote plugins) - `vim.loop`: module that exposes the functionality of Neovim's event-loop (using LibUV) - `vim.lsp`: module that controls the built-in LSP client - `vim.treesitter`: module that exposes the functionality of the tree-sitter library This list is by no means comprehensive. If you wish to know more about what's made available by the `vim` variable, |lua-stdlib| and |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 |api-global|. Tips~ 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: > function _G.dump(...) local objects = vim.tbl_map(vim.inspect, {...}) print(unpack(objects)) return ... end < You can then inspect the contents of an object very quickly in your code or from the command-line: > dump({1, 2, 3}) < > :lua dump(vim.loop) < 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. ============================================================================== USING VIMSCRIPT FROM LUA *luaguide-using-vimscript-from-lua* vim.api.nvim_eval()~ This function evaluates a Vimscript expression string and returns its value. Vimscript data types are automatically converted to Lua types (and vice versa). It is the Lua equivalent of the `luaeval()` function in Vimscript > -- Data types are converted correctly print(vim.api.nvim_eval('1 + 1')) -- 2 print(vim.inspect(vim.api.nvim_eval('[1, 2, 3]'))) -- { 1, 2, 3 } print(vim.inspect(vim.api.nvim_eval('{"foo": "bar", "baz": "qux"}'))) -- { baz = "qux", foo = "bar" } print(vim.api.nvim_eval('v:true')) -- true print(vim.api.nvim_eval('v:null')) -- nil < *Todo tasks: is it possible for `vim.api.nvim_eval()` to return a `funcref`? Caveats~ Unlike `luaeval()`, `vim.api.nvim_eval()` does not provide an implicit `_A` variable to pass data to the expression. vim.api.nvim_exec()~ 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). > local result = vim.api.nvim_exec( [[ let mytext = 'hello world' function! MyFunction(text) echo a:text endfunction call MyFunction(mytext) ]], true) print(result) -- 'hello world' < *Todo tasks: The docs say that script-scope (`s:`) is supported, but running this snippet with a script-scoped variable throws an error. Why? vim.api.nvim_command()~ This function executes an ex command. It takes in a string containing the command to execute. > vim.api.nvim_command('new') vim.api.nvim_command('wincmd H') vim.api.nvim_command('set nonumber') vim.api.nvim_command('%s/foo/bar/g') < vim.cmd()~ Alias for `vim.api.nvim_exec()`. Only the command argument is needed, `output` is always set to `false`. > vim.cmd('buffers') vim.cmd([[ let g:multiline =<< EOF foo bar baz EOF ]]) < Tips~ Since you have to pass strings to these functions, you often end up having to escape backslashes: > vim.cmd('%s/\\Vfoo/bar/g') < Literal strings are easier to use as they do not require escaping characters: > vim.cmd([[%s/\Vfoo/bar/g]]) < vim.api.nvim_replace_termcodes()~ This API function allows you to escape terminal codes and Vim keycodes. You may have come across mappings like this one: > inoremap pumvisible() ? "\" : "\" < Trying to do the same in Lua can prove to be a challenge. You might be tempted to do it like this: > function _G.smart_tab() return vim.fn.pumvisible() == 1 and [[\]] or [[\]] end vim.api.nvim_set_keymap('i', '', 'v:lua.smart_tab()', {expr = true, noremap = true}) < only to find out that the mapping inserts `\` and `\` literally... 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. Lua doesn't have such a feature built-in. Fortunately, Neovim has an API function for escaping terminal codes and keycodes: `nvim_replace_termcodes()` > print(vim.api.nvim_replace_termcodes('', true, true, true)) < This is a little verbose. Making a reusable wrapper can help: > -- The function is called `t` for `termcodes`. -- You don't have to call it that, but I find the terseness convenient local function t(str) -- Adjust boolean arguments as needed return vim.api.nvim_replace_termcodes(str, true, true, true) end print(t'') < Coming back to our earlier example, this should now work as expected: > local function t(str) return vim.api.nvim_replace_termcodes(str, true, true, true) end function _G.smart_tab() return vim.fn.pumvisible() == 1 and t'' or t'' end vim.api.nvim_set_keymap('i', '', 'v:lua.smart_tab()', {expr = true, noremap = true}) < See also: - |keycodes| - |expr-quote| - |nvim_replace_termcodes()| ============================================================================== MANAGING VIM OPTIONS *luaguide-managing-vim-options* Using api functions~ Neovim provides a set of API functions to either set an option or get its current value: - Global options: - |nvim_set_option()| - |nvim_get_option()| - Buffer-local options: - |nvim_buf_set_option()| - |nvim_buf_get_option()| - Window-local options: - |nvim_win_set_option()| - |nvim_win_get_option()| They take a string containing the name of the option to set/get as well as the value you want to set it to. Boolean options (like `(no)number`) have to be set to either `true` or `false`: > vim.api.nvim_set_option('smarttab', false) print(vim.api.nvim_get_option('smarttab')) -- false < Unsurprisingly, string options have to be set to a string: > vim.api.nvim_set_option('selection', 'exclusive') print(vim.api.nvim_get_option('selection')) -- 'exclusive' < Number options accept a number: > vim.api.nvim_set_option('updatetime', 3000) print(vim.api.nvim_get_option('updatetime')) -- 3000 < Buffer-local and window-local options also need a buffer number or a window number (using `0` will set/get the option for the current buffer/window): > vim.api.nvim_win_set_option(0, 'number', true) vim.api.nvim_buf_set_option(10, 'shiftwidth', 4) print(vim.api.nvim_win_get_option(0, 'number')) -- true print(vim.api.nvim_buf_get_option(10, 'shiftwidth')) -- 4 < Using meta-accessors~ 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: - |vim.o|: behaves like `:set` - |vim.go|: behaves like `:setglobal` - |vim.bo|: behaves like `:setlocal` for buffer-local options - |vim.wo|: behaves like `:setlocal` for window-local options > vim.o.smarttab = false print(vim.o.smarttab) -- false vim.o.isfname = vim.o.isfname .. ',@-@' -- on Linux: set isfname+=@-@ print(vim.o.isfname) -- '@,48-57,/,.,-,_,+,,,#,$,%,~,=,@-@' vim.bo.shiftwidth = 4 print(vim.bo.shiftwidth) -- 4 < You can specify a number for buffer-local and window-local options. If no number is given, the current buffer/window is used: > vim.bo[4].expandtab = true -- same as vim.api.nvim_buf_set_option(4, 'expandtab', true) vim.wo.number = true -- same as vim.api.nvim_win_set_option(0, 'number', true) < 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`: - `vim.opt`: behaves like `:set` - `vim.opt_global`: behaves like `:setglobal` - `vim.opt_local`: behaves like `:setlocal` > vim.opt.smarttab = false print(vim.opt.smarttab:get()) -- false < Some options can be set using Lua tables: > vim.opt.completeopt = {'menuone', 'noselect'} print(vim.inspect(vim.opt.completeopt:get())) -- { "menuone", "noselect" } < 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. > vim.opt.shortmess:append({ I = true }) -- alternative form: vim.opt.shortmess = vim.opt.shortmess + { I = true } vim.opt.whichwrap:remove({ 'b', 's' }) -- alternative form: vim.opt.whichwrap = vim.opt.whichwrap - { 'b', 's' } < Be sure to look at |vim.opt| for more information. See also: - |lua-vim-options| ============================================================================== MANAGING VIM INTERNAL VARIABLES *luaguide-managing-vim-internal-variables* Using api functions~ Much like options, internal variables have their own set of API functions: - Global variables (`g:`): - |nvim_set_var()| - |nvim_get_var()| - |nvim_del_var()| - Buffer variables (`b:`): - |nvim_buf_set_var()| - |nvim_buf_get_var()| - |nvim_buf_del_var()| - Window variables (`w:`): - |nvim_win_set_var()| - |nvim_win_get_var()| - |nvim_win_del_var()| - Tabpage variables (`t:`): - |nvim_tabpage_set_var()| - |nvim_tabpage_get_var()| - |nvim_tabpage_del_var()| - Predefined Vim variables (`v:`): - |nvim_set_vvar()| - |nvim_get_vvar()| 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, |internal-variables| describes them in detail. These functions take a string containing the name of the variable to set/get/delete as well as the value you want to set it to. > vim.api.nvim_set_var('some_global_variable', { key1 = 'value', key2 = 300 }) print(vim.inspect(vim.api.nvim_get_var('some_global_variable'))) -- { key1 = "value", key2 = 300 } vim.api.nvim_del_var('some_global_variable') < 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): > vim.api.nvim_win_set_var(0, 'some_window_variable', 2500) vim.api.nvim_tab_set_var(3, 'some_tabpage_variable', 'hello world') print(vim.api.nvim_win_get_var(0, 'some_window_variable')) -- 2500 print(vim.api.nvim_buf_get_var(3, 'some_tabpage_variable')) -- 'hello world' vim.api.nvim_win_del_var(0, 'some_window_variable') vim.api.nvim_buf_del_var(3, 'some_tabpage_variable') < Using meta-accessors~ Internal variables can be manipulated more intuitively using these meta-accessors: - |vim.g|: global variables - |vim.b|: buffer variables - |vim.w|: window variables - |vim.t|: tabpage variables - |vim.v|: predefined Vim variables - |vim.env|: environment variables > vim.g.some_global_variable = { key1 = 'value', key2 = 300 } print(vim.inspect(vim.g.some_global_variable)) -- { key1 = "value", key2 = 300 } < 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']`. To delete one of these variables, simply assign `nil` to it: > vim.g.some_global_variable = nil < See also: - |lua-vim-variables| Caveats~ Unlike options meta-accessors, you cannot specify a number for buffer/window/tabpage-scoped variables. Additionally, 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: > let g:variable = {} lua vim.g.variable.key = 'a' echo g:variable " {} < You can use a temporary variable as a workaround: > let g:variable = {} lua << EOF local tmp = vim.g.variable tmp.key = 'a' vim.g.variable = tmp EOF echo g:variable " {'key': 'a'} < This is a known issue: - Issue #12544: https://github.com/neovim/neovim/issues/12544 ============================================================================== CALLING VIMSCRIPT FUNCTIONS *luaguide-calling-vimscript-functions* vim.fn.{function}()~ `vim.fn` can be used to call a Vimscript function. Data types are converted back and forth from Lua to Vimscript. > print(vim.fn.printf('Hello from %s', 'Lua')) local reversed_list = vim.fn.reverse({ 'a', 'b', 'c' }) print(vim.inspect(reversed_list)) -- { "c", "b", "a" } local function print_stdout(chan_id, data, name) print(data[1]) end vim.fn.jobstart('ls', { on_stdout = print_stdout }) < Hashes (`#`) are not valid characters for indentifiers in Lua, so autoload functions have to be called with this syntax: > vim.fn['my#autoload#function']() < The functionality of `vim.fn` is identical to `vim.call`, but allows a more Lua-like syntax. 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. See also: - |vim.fn| Tips~ Neovim has an extensive library of powerful built-in functions that are very useful for plugins. See |vim-function| for an alphabetical list and |function-list| for a list of functions grouped by topic. Neovim API functions can be used directly through `vim.api.{..}`. See |api| for information. Caveats~ 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: > if has('nvim') " do something... endif < 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`: > if vim.fn.has('nvim') == 1 then -- do something... end < ============================================================================== DEFINING MAPPINGS *luaguide-defining-mappings* Neovim provides a list of API functions to set, get and delete mappings: - Global mappings: - |nvim_set_keymap()| - |nvim_get_keymap()| - |nvim_del_keymap()| - Buffer-local mappings: - |nvim_buf_set_keymap()| - |nvim_buf_get_keymap()| - |nvim_buf_del_keymap()| Let's start with `vim.api.nvim_set_keymap()` and `vim.api.nvim_buf_set_keymap()` The first argument passed to the function is a string containing the name of the mode for which the mapping will take effect: | String value | Help page | Affected modes | Vimscript equivalent | | ---------------------- | ------------- | ---------------------------------------- | -------------------- | | `''` (an empty string) | `mapmode-nvo` | Normal, Visual, Select, Operator-pending | `:map` | | `'n'` | `mapmode-n` | Normal | `:nmap` | | `'v'` | `mapmode-v` | Visual and Select | `:vmap` | | `'s'` | `mapmode-s` | Select | `:smap` | | `'x'` | `mapmode-x` | Visual | `:xmap` | | `'o'` | `mapmode-o` | Operator-pending | `:omap` | | `'!'` | `mapmode-ic` | Insert and Command-line | `:map!` | | `'i'` | `mapmode-i` | Insert | `:imap` | | `'l'` | `mapmode-l` | Insert, Command-line, Lang-Arg | `:lmap` | | `'c'` | `mapmode-c` | Command-line | `:cmap` | | `'t'` | `mapmode-t` | Terminal | `:tmap` | 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 ``, which disables a key. The third argument is a string containing the right-hand side of the mapping (the command to execute). The final argument is a table containing boolean options for the mapping as defined in |:map-arguments|. Buffer-local mappings also take a buffer number as their first argument (`0` sets the mapping for the current buffer). > vim.api.nvim_set_keymap('n', '', ':set hlsearch!', { noremap = true, silent = true }) -- :nnoremap :set hlsearch vim.api.nvim_set_keymap('n', 'tegf', [[lua require('telescope.builtin').git_files()]], { noremap = true, silent = true }) -- :nnoremap tegf lua require('telescope.builtin').git_files() vim.api.nvim_buf_set_keymap(0, '', 'cc', 'line(".") == 1 ? "cc" : "ggcc"', { noremap = true, expr = true }) -- :noremap cc line('.') == 1 ? 'cc' : 'ggcc' < `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. > print(vim.inspect(vim.api.nvim_get_keymap('n'))) -- :verbose nmap < `vim.api.nvim_buf_get_keymap()` takes an additional buffer number as its first argument (`0` will get mapppings for the current bufffer) > print(vim.inspect(vim.api.nvim_buf_get_keymap(0, 'i'))) -- :verbose imap < `vim.api.nvim_del_keymap()` takes a mode and the left-hand side of a mapping. > vim.api.nvim_del_keymap('n', '') -- :nunmap < Again, `vim.api.nvim_buf_del_keymap()`, takes a buffer number as its first argument, with `0` representing the current buffer. > vim.api.nvim_buf_del_keymap(0, 'i', '') -- :iunmap < ============================================================================== DEFINING USER COMMANDS *luaguide-defining-user-commands* There is currently no interface to create user commands in Lua. It is planned, though: - Pull request #11613: https://github.com/neovim/neovim/pull/11613 For the time being, you're probably better off creating commands in Vimscript. ============================================================================== DEFINING AUTOCOMMANDS *luaguide-defining-autocommands* Augroups and autocommands do not have an interface yet but it is being worked on: - Pull request #12378: https://github.com/neovim/neovim/pull/12378 - Pull request #14661: https://github.com/neovim/neovim/pull/14661 lua: autocmds take 2 In the meantime, you can either create autocommands in Vimscript or use this wrapper from norcalli/nvim_utils: https://github.com/norcalli/nvim_utils/blob/master/lua/nvim_utils.lua#L554-L567 ============================================================================== DEFINING SYNTAX/HIGHLIGHTS *luaguide-defining-syntax-highlights* The syntax API is still a work in progress. Here are a couple of pointers: - Issue #9876: https://github.com/neovim/neovim/issues/9876 - tjdevries/colorbuddy.vim, a library for creating colorschemes in Lua: https://github.com/tjdevries/colorbuddy.vim - |lua-treesitter| ============================================================================== GENERAL TIPS AND RECOMMENDATIONS *luaguide-general-tips-and-recommendations* Reloading cached modules~ 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. If you'd like to refresh the cache for a particular module, you have to modify the `package.loaded` global table: > package.loaded['modname'] = nil require('modname') -- loads an updated version of module 'modname' < 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. Notes about Vimscript <-> Lua type conversion~ Converting a variable creates a copy:~ You can't directly interact with the reference to a Vim object from Lua or a Lua object from Vimscript. For example, the `map()` function in Vimscript modifies a variable in place: > let s:list = [1, 2, 3] let s:newlist = map(s:list, {_, v -> v * 2}) echo s:list " [2, 4, 6] echo s:newlist " [2, 4, 6] < Using this function from Lua creates a copy instead: > local tbl = {1, 2, 3} local newtbl = vim.fn.map(tbl, function(_, v) return v * 2 end) print(vim.inspect(tbl)) -- { 1, 2, 3 } print(vim.inspect(newtbl)) -- { 2, 4, 6 } < Conversion is not always possible~ This mostly affects functions and tables: Lua tables that are a mix between a List and a Dictionary can't be converted: > print(vim.fn.count({1, 1, number = 1}, 1)) -- E5100: Cannot convert given lua table: table should either have a sequence of positive integer keys or contain only string keys < While you can call Vim functions in Lua with `vim.fn`, you can't hold references to them. This can cause surprising behaviors: > local FugitiveHead = vim.fn.funcref('FugitiveHead') print(FugitiveHead) -- vim.NIL vim.cmd("let g:test_dict = {'test_lambda': {-> 1}}") print(vim.g.test_dict.test_lambda) -- nil print(vim.inspect(vim.g.test_dict)) -- {} < Passing Lua functions to Vim functions is OK, storing them in Vim variables is not: > -- This works: vim.fn.jobstart({'ls'}, { on_stdout = function(chan_id, data, name) print(vim.inspect(data)) end }) -- This doesn't: vim.g.test_dict = {test_lambda = function() return 1 end} -- Error: Cannot convert given lua type < Note however that doing the same from Vimscript with `luaeval()` **does** work: > let g:test_dict = {'test_lambda': luaeval('function() return 1 end')} echo g:test_dict " {'test_lambda': function('4714')} < Vim booleans~ 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. Lua booleans are converted to actual booleans in Vimscript, not numbers: > lua vim.g.lua_true = true echo g:lua_true " v:true lua vim.g.lua_false = false echo g:lua_false " v:false < Setting up linters/language servers~ 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: luacheck~ 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` : > globals = { "vim", } < The Alloyed/lua-lsp: https://github.com/Alloyed/lua-lsp/ language server uses `luacheck` to provide linting and reads the same file. For more information on how to configure `luacheck`, please refer to its documentation: https://luacheck.readthedocs.io/en/stable/config.html sumneko/lua-language-server~ 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/CONFIG.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 without VSCode": https://github.com/sumneko/lua-language-server/wiki/Setting-without-VSCode coc.nvim~ 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. Debugging Lua code~ 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/ . Testing Lua code~ - plenary.nvim: test harness: https://github.com/nvim-lua/plenary.nvim/#plenarytest_harness - notomo/vusted: https://github.com/notomo/vusted Using Luarocks packages~ 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 ============================================================================== MISCELLANEOUS *luaguide-miscellaneous* vim.loop~ `vim.loop` is the module that exposes the LibUV API. Some resources: - Official documentation for LibUV: https://docs.libuv.org/en/v1.x/ - Luv documentation: https://github.com/luvit/luv/blob/master/docs.md - teukka.tech - Using LibUV in Neovim: https://teukka.tech/posts/2020-01-07-vimloop/ See also: - |vim.loop| vim.lsp~ `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. The behavior of the client can be configured using "lsp-handlers". For more information: - |lsp-handler| - neovim/neovim#12655: https://github.com/neovim/neovim/pull/12655 - How to migrate from diagnostic-nvim: https://github.com/nvim-lua/diagnostic-nvim/issues/73#issue-737897078 You may also want to take a look at plugins built around the LSP client: https://github.com/rockerBOO/awesome-neovim#lsp See also: - |lsp| vim.treesitter~ `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 . The nvim-treesitter: https://github.com/nvim-treesitter/ organisation hosts various plugins taking advantage of the library. See also: - |lua-treesitter| Transpilers~ One advantage of using Lua is that you don't actually have to write Lua code! There is a multitude of transpilers available for the language. - Moonscript: https://moonscript.org/ 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. - Fennel: https://fennel-lang.org/ 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 . Other interesting projects: - TypeScriptToLua/TypeScriptToLua: https://github.com/TypeScriptToLua/TypeScriptToLua - teal-language/tl: https://github.com/teal-language/tl - Haxe: https://haxe.org/ - SwadicalRag/wasm2lua: https://github.com/SwadicalRag/wasm2lua - hengestone/lua-languages: https://github.com/hengestone/lua-languages vim:tw=78:ts=8:noet:ft=help:norl: