Is it possible for the language server to deduce the members of a metatable?

[drcxd]

Assume I am trying to use OOP in Lua in the following manner:

local Class = {}
Class.__index = Class

Class.myMethod = function () print("hellow world") end

Class.new = function ()
  local o = {}
  setmetatable(o, Class)
  return o
end

local inst = Class.new()
inst:myMethod()
     ^

It seems that when I input till the colon, the language server can not figure out that inst has a metatable which __index is set to Class, and thus can not prompt completion for myMythod. Is this impossible to figure out since it is a runtime thing? Do you have any recommended pattern to implement the similar effect, but make the language server know the existence of the methods or member variables?

[tomlau10]

LuaLS requires annotations to perform better type infer.
I think you will need some @class annotation in your provided snippet
https://luals.github.io/wiki/annotations/#class

---@class Class
local Class = {}
Class.__index = Class

Class.myMethod = function () print("hellow world") end

Class.new = function ()
  ---@class Class
  local o = {}
  -- you can define other fields for `o` here
  -- which will be auto "injected" into the class `Class` as member fields
  o.x = 1
  o.y = 2
  setmetatable(o, Class)
  return o
end

local inst = Class.new()  -- server will infer that `Class.new -> Class`
inst:my --> now this will have completion for `myMethod`

[drcxd]

Thanks a lot. This perfectly solves my problem. I did not know that annotation is necessary, should have read the documentation more carefully.