LÖVE

Checking the value of a Lua variable during debugging is often invaluable and print() is a commonly used debugging tool. But what about complex table values? Many Lua programmers have written their own pretty-printer or data dumper and some even use it for (de-)serializing Lua data structures. But this seems to reach its limit when one takes cyclic references, metatables, upvalues and environment tables into account.
This module dumps arbitrarily complex Lua values as GraphViz .dot-files that can be transformed into a variety of image formats.

local up1 = false
local up2 = io.stdout
local t1 = { val = 1 }
local t2 = { val = 2 }
setmetatable( t1, { __index = function( t, k )
  if t2[ k ] ~= nil then
    return t2[ k ]
  else
    return up1 or up2
  end
end } )
setmetatable( t2, { __index = t1 } )

• Microscope Project page
• Source (Github repo)
• GraphViz