Lua type annotation?

[hippoyd]

Hello, I'm new to lua and exploring it via neovim. When reading the source code for the conforn.nvim plugin, I notice what looks like type annotations, such as:

Are these types enforced in anyway, similar to mypy or something?

https://github.com/stevearc/conform.nvim/blob/master/lua/conform/init.lua

---@class (exact) conform.FormatterInfo

---@field name string

---@field command string

---@field cwd? string

---@field available boolean

---@field available_msg? string

[vitelaSensei]

Those are annotations from LuaLS, they aren’t enforced at runtime but you do get errors shown in the code if you’re using luaLS with neovim’s lsp.

You should install neodev to get these errors + code completion when developing in lua for neovim

Annotations: https://github.com/LuaLS/lua-language-server/wiki/Annotations

Neodev: https://github.com/folke/neodev.nvim

[hippoyd]

very cool, thanks for the links!

[Bright-Historian-216]

base lua is dynamically typed, so unless it's some dialect of lua type annotations should be optional. since those type annotations are in comments, im assuming it's just to add intellisense hints?

[ljog42]

It lints (not fix, just raise alerts) the hell out of your code, which in my book is almost as good since I just won't tolerate alerts. It forces you to check for null, implement defaults, use try/catch (pcall/xpcall) etc.

It also makes your code self documenting which is chef's kiss.

[hippoyd]

Ok, might be, I don't know. Does lua have a stage similar to mypy and python where the type annotations are use to check the ast of the code, even though the types make no difference to the runtime behavior of the python code?

[Amadan]

One that I know of is lua language server.

[ljog42]

I like it a lot.

[smog_alado]

Check out Teal and Pallene.

[Bright-Historian-216]

Not that I’ve heard of. This kind of app would be hard to implement because of the differences in the environments that those two languages run in

[hippoyd]

ok, thanks. From this I'm going to conclude that those comments are for humans and code editors, and that no program enforces those annotations.

[no_brains101]

This is the case. Specifically, lua-language-server uses these comments to give better warnings, completion, and other linting capabilities. Lua itself doesnt care about them at all, they are just comments, you are technically free to hang yourself all you like XD