How can I dynamically copy the luau type from one table, to another

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#1

I want luau typechecking for my networking module to function correctly- it has an initialize function that gets passed a table, and that table is then deep-copied by a function, into each new piece of data that the module creates.

My question, is how can I copy the original initialize table’s typechecking autofill stuff, to work on all tables I deep copy it from? Is there some way I can do something like

local DefaultTable = InitializeInitializeCallResult -- The table sent at runtime by an Initialize function call. I am willing to change this setup though, if it's necessary
type DefaultTableType = DefaultTable.Type

-- later when the data is being made
local NewData: DefaultTableType = DeepCopy(DefaultTable) -- DeepCopy does some special stuff in how it handles recursive tables

and have something like that just copy-paste whatever typechecking? In my example, DefaultTable can be a different value everu project, and I’d like to not have to manually make a type to mimic that table if possible.

#2

I think you mean this?

local defaultTable = require(someModule)

local newData: typeof(someTable) = deepCopy(defaultTable)

Or you can explicitly return the generic type of the argument passed:

--!strict

local function deepCopy<T>(t: T): T
	t = table.clone(t :: any) :: any -- ignore type check for t and table.clone

	for index: any, value: any in t :: any do -- ignore type check for table iteration
		if typeof(value) == "table" then
			(t :: any)[index] = deepCopy(value) -- ignore type check for table indexing
		end
	end

	return t
end

local a = deepCopy({key1 = true}) -- intellisense of t argument

If there are dynamic keys being added and/or the variable is not statically typed, then no it is not possible. You can kinda merge table types by doing something like

local newData: typeof(someTable) & typeof(anotherTable) = someMergingOperation()
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#3

Typof can be used to “copy” whatever type a table has? And it’s a “static” table in the sense that it’s from a function that’s only ever called once… but if it won’t work for a function, I’m game for moving it over to be a table property you assign in the module.

Sounds like it might be what I wanted, gonna test it out tonight.