table.print function with custom sink support and circular reference detection.

tableprint.lua

local pairs = pairs
local type = type
local tostring = tostring
local print = print
local table = table
local next = next

module "tableprint"

local function tableprint(t, tab, sink, cache)
    for k, v in pairs(t) do
        if type(v) ~= "table" then
            sink(("%s%s: %s (%s)"):format(tab, tostring(k), tostring(v), type(v)))
        else
            local id = cache[v] or cache.id + 1
            sink(("%s%s: (table) #%d"):format(tab, tostring(k), id))
            if not next(v) then
                sink(tab .. "\t(empty)")
            else
                if cache[v] then
                    sink(tab .. "\t...")
                else
                    cache[v] = id
                    cache.id = id
                    tableprint(v, tab .. "\t", sink, cache)
                end
            end
        end
    end
end

defaultSink = print

function table.print(t, sink)
    sink = sink or defaultSink
    tableprint(t, "", sink, {[t] = 0, id = 0})
end