Re: controlling library load

[Javier Guerra Giraldez <javier@...>]

might be too naive, but this sounds doable with a single global state.

---
local old_require = require
local stateOpen = false

function my_require(lib)
    if stateOpen then
        return old_require(lib)
    end

    if allow_list(lib) then
        local prev_state = stateOpen
        stateOpen = true
        local r = old_require(lib)
        stateOpen = prev_state
        return r
    end
end
----

here i'm using the call stack to return the global to the previous
state.  perhaps a <close> variable would be better.


On Fri, 23 Sept 2022 at 13:23, Viacheslav Usov <via.usov@gmail.com> wrote:
>
> If anything like this has been done before, kindly point me to that.
>
> I have an application that hosts one or more lua_State instances. I
> want to control what libraries a given instance can load. For that
> purpose, I have disabled the default searchers (except the preload)
> and have my own searcher that decides what can be loaded. I have also
> replaced the global 'require' with my own function, which currently
> just calls (eventually) into the original require. So I can already
> control what libraries a given instance can load, no problem.
>
> Now I'd like to make this a bit more sophisticated. I want to be able
> to say that if library X can be loaded, then all the libraries that X
> loads directly or indirectly can also be loaded, without having to
> specify them upfront.
>
> For that I have to overcome a few hurdles. The biggest as it seems to
> me today is that I will have to understand that library Y is requested
> directly or indirectly by X (or not). I am not exactly sure how this
> can be done.
>
> In principle, I'd be interested in a design that works equally with
> native and pure Lua libraries. But one that works only with pure Lua
> libraries would also be a good step forward. To simplify this even
> more for the sake of understanding, let's only tackle the direct
> require case, i.e., X just does require(Y). In the latter case, I
> presume I can use the debug API to examine the call stack and
> understand where the call originates. I will need to make sure that
> anything that I load gets tagged properly to use the debug API
> efficiently. To handle indirect loads, I will have to tag
> implicitly-permitted libraries differently from explicitly-permitted,
> recursively. This seems messy but will probably work. Is there a
> better way?
>
> Any advice is appreciated.
>
> Cheers,
> V.



-- 
Javier