Re: Using Lua for config files

[Petite Abeille <petite.abeille@...>]

On Dec 19, 2013, at 1:59 PM, John Hind <john.hind@zen.co.uk> wrote:

> Rather than controlling what users can do, I would prefer to control the effect they can have. Why should they not have the benefit of a full featured language to configure your program?

Through their eggnog induced torpor, the elves have this to say: 

Let it be, let it be, let it be, let it be 
There will be an answer, let it be 

What about some sort of Hippocratic Lua script: primum non nocere?

For example:

(1) Hook it

local naughty = {}
local aHook = function( anEvent, aLine )
  naughty[ aLine ] = ( naughty[ aLine ] or 0 )  + 1
  assert(  naughty[ aLine ] <= 10, 'naughty!' )
end

(2) Set it

debug.setmetatable( '', nil )
debug.setmetatable( 1, nil )
debug.setmetatable( function() end, nil )
debug.setmetatable( true, nil )
debug.sethook ( aHook, 'l' )

local anEnvironment = {}
anEnvironment._G = anEnvironment

(3) Load it

local aConfig = assert( load( io.open( 'TestConfig.txt', 'r' ):read( 1000 ), 'config', 't', anEnvironment ) )

aConfig()

debug.sethook()

Marvel in puzzlement:

for aKey, aValue in pairs( anEnvironment ) do
  print( aKey, aValue )
end

> 1	1
> 2	2
> 3	3
> 4	4
> 5	5
> foo	bar
> cool	1
> list	table: 0x7feffb408fe0
> _G	table: 0x7feffb407f00

—8<—

--something = ("x"):rep(100000000)

list = {}

for anIndex = 1, 5 do
 _G[ anIndex ] = anIndex
end

if true then
  foo = 'bar'
else
  foo = 'baz'
end

local function nice()
  return 1
end

cool = nice()

local function naughty()
  naughty()
end

--naughty()

--while true do end


—>8—


What could ever possibly go wrong ask the elves?