Re: [PATCH v1 6/8] box: export _func functions with box.func folder

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Thu, May 30, 2019 at 01:45:33PM +0300, Kirill Shcherbatov wrote:
> Closes #4182
> Needed for #1260
> 
> @TarantoolBot document
> Title: Persistent Lua functions
> 
> Lua functions managed by Tarantool are called 'persistent'.
> They are stored in snapshoot and are available after server
> restart.
> Persistent Lua functions are exported in box.schema.func.persistent
> folder. They may be called via .call exported object method or
> via netbox:call.
> 
> Some restrictions must be accounted writing such routines:
> 1. only limited set of Lua functions and modules are available:
> -assert -error -pairs -ipairs -next -pcall -xpcall -type
> -print -select -string -tonumber -tostring -unpack -math -utf8;
> 2. global variables are forbidden.
> 
> Moreover all functions and their metadata are now exported in
> box.func table (not only persistent). Persistent Lua functions
> have box.func.FUNCNAME.call() method to execute it in interactive
> console.
> Persistent Lua functions are also available with net.box call.
> 
> Example:
> lua_code = [[function(a, b) return a + b end]]
> box.schema.func.create('sum', {
>                        body = lua_code, is_deterministic = true,
>                        returns = 'integer', is_deterministic = true})
> box.func.sum
> - call: 'function: 0x4016b6a0'
>   returns: integer
>   is_deterministic: true
>   id: 2
>   language: LUA
>   name: sum
>   is_persistent: true
>   setuid: false
> 
> box.func.sum.call(1, 2)

Also, what about access checks? I may be wrong, but it looks like anyone
can call a function this way in your implementation. I guess we should
check 'execute' permission.