[네오빔에서 first-class 언어](https://github.com/neovim/neovim/wiki/FAQ#why-embed-lua-instead-of-x)로서 [통합된 루아](https://www.youtube.com/watch?v=IP3J56sKtn0)는 킬러 피쳐들 중 하나로 자리잡고 있습니다.
하지만 루아로 플러그인 작성하는 방법에 대해 배울 수 있는 자료는 빔스크립트로 작성하는 방법에 비해 많지 않습니다.
- ['X를 Y분 만에 배우자'의 루아 페이지](https://learnxinyminutes.com/docs/lua/)에서는 기본적인 것들을 빠르게 훑어볼 수 있습니다.
- [이 가이드](https://github.com/medwatt/알림s/blob/main/Lua/Lua_Quick_Guide.ipynb)도 빠르게 시작하기 좋은 자료입니다.
- 당신이 비디오로 배우는 것을 더 선호한다면 Derek Banas의 [1 시간짜리 튜토리얼](https://www.youtube.com/watch?v=iMacxZQMPXs)도 있습니다.
- 실행 가능한 예제와 함께 좀 더 인터랙티브하게 배우고 싶다면 [루아 스크립트 튜토리얼](https://www.luascript.dev/learn)도 있습니다.
- [루아 유저 위키](http://lua-users.org/wiki/LuaDirectory)에는 루아와 관련된 유용한 정보들이 많이 있습니다.
- [루아 공식 레퍼런스 매뉴얼](https://www.lua.org/manual/5.1/)은 가장 광범위한 자료를 둘러볼 수 있습니다.(빔 에디터 내에서 읽고 싶다면 Vimdoc 플러그인으로도 있습니다.: [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!
Neovim은 `init.vim` 대신 `init.lua` 파일을 설정(configuration) 파일로 로딩할 수도 있습니다.
알림: `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.
루아 모듈들은 Neovim의 `runtimepath` (대부분의 \*nix 시스템 [*맥 | 리눅스*] 에서는 `~/.config/nvim/lua`, 윈도우에서는 `~/AppData/Local/nvim/lua` ) 안의 `lua/` 폴더 안에 위치합니다. 이 폴더 안에 있는 루아 파일들은 모듈로서 `require()` 할 수 있습니다.
루아 플러그인들 중 몇몇은 그 플러그인의 `lua/` 폴더 안에 동일한 파일 이름이 존재할 수도 있습니다. 그럴 경우 이름공간([namespace](https://ko.wikipedia.org/wiki/%EC%9D%B4%EB%A6%84%EA%B3%B5%EA%B0%84)) 충돌로 이어질 수 있습니다.
만약 두개의 다른 플러그인이 `lua/main.lua` 파일을 가지고 있다면, `require('main')` 을 실행할 때 어떤 파일을 불러야 하는지 알기 힘듭니다.
`:runtime`은 조금 다릅니다: `runtimepath` 옵션을 사용해서 어떤 파일을 가져올지 정할 수 있습니다. 더 많은 정보는 [`:help :runtime`](https://neovim.io/doc/user/repeat.html#:runtime)에서 확인할 수 있습니다.
- 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).
It is the Lua equivalent of the `luaeval()` function in Vimscript
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.
Lua doesn't have such a feature built-in. Fortunately, Neovim has an API function for escaping terminal codes and keycodes: `nvim_replace_termcodes()`
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.
```lua
vim.opt.shortmess:append({ I = true })
-- alternative form:
vim.opt.shortmess = vim.opt.shortmess + { I = true }
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:
```vim
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`:
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 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 [`: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.
```lua
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)
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:
The first argument passed to this function is the name of the command (which must start with an uppercase letter).
The second argument is the code to execute when invoking said command. It can either be:
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).
-- return completion candidates as a list-like table
return { 'foo', 'bar', 'baz' }
end,
})
```
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.
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.
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:
let g:test_dict = {'test_lambda': luaeval('function() return 1 end')}
echo g:test_dict
" {'test_lambda': function('<lambda>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:
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`):
```lua
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)
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).
The [nvim-treesitter](https://github.com/nvim-treesitter/) organisation hosts various plugins taking advantage of the library.
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.
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
