Add "import" Function and "UNSAFE_NO_SANDBOX" Flag for Accessing Built-in Lua Objects & Functions

[AntumDeluge]

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Hoping this is a more acceptable solution than #308.

This adds an import function which is enabled with the UNSAFE_NO_SANDBOX command line flag & is used to access built-in Lua objects & functions within the config.ld file.

Example config.ld:

local print = import("print")
local string = import("string")

for _, s in ipairs({string.split("Hello world!")}) do
	print(s)
end

project = "foo"
title = "Bar"
file = {"init.lua"}

Example execution:

ldoc --UNSAFE_NO_SANDBOX .

[nawordar]

Is it necessary to make the flag SCREAM_CASE? I have never seen it used in command arguments. --disable_sandbox fits the current naming scheme and looks better.

[AntumDeluge]

Is it necessary to make the flag SCREAM_CASE?

No.

[alerque]

I would be okay dropping the use of SCREAM_CASE, but I think we should keep the urgent verbose tone with the words "unsafe" and a negative "no", so --unsafe_no_sandbox. The only other alternative might be to split this into two flags and require both, e.g. --no-sandbox, but require a --unsafe flag to enable unsafe feature(s). If we think there might be more than one we want to warn about like this perhaps that would be best.

[AntumDeluge]

Changed UNSAFE_NO_SANDBOX to unsafe_no_sandbox.