Dumping a description of a Lua value

dump.lua

local dump_table_threshold = 3
local dump_indent = (" "):rep(4)

local dumptable = {
    ["nil"] = tostring,
    ["number"] = tostring,
    ["string"] = function(value) return "\"" .. value .. "\"" end,
    ["boolean"] = tostring,
    ["table"] = function(value, depth, markers)
        if markers[value] then
            return "recursively-referenced table"
        end
        markers[value] = true
        
        local lines = setmetatable({}, {__index = table})
        local indices = {}
        local long = false
        for i, v in ipairs(value) do
            local vstr, l = dumpstr(v, depth + 1, markers)
            lines:insert(vstr)
            indices[i] = true
            long = long or l
        end
        for k, v in pairs(value) do
            if not indices[k] then
                local kstr, l1 = dumpstr(k, depth + 1, markers)
                local vstr, l2 = dumpstr(v, depth + 1, markers)
                lines:insert("[" .. kstr .. "] = " .. vstr)
                long = long or l1 or l2
            end
        end
        
        long = long or (#lines > dump_table_threshold)
        local result = "{"
        for i, line in ipairs(lines) do
            if i ~= 1 then
                result = result .. ", "
            end
            if long then
                result = result .. "\n" .. dump_indent:rep(depth + 1)
            end
            result = result .. line
            
        end
        if long then
            result = result .. "\n" .. dump_indent:rep(depth)
        end
        result = result .. "}"
        
        markers[value] = nil
        return result, long
    end,
    ["function"] = tostring,
    ["thread"] = tostring,
    ["userdata"] = tostring
}

function dumpstr(value, depth, markers)
    if not depth then
        depth = 0
    end
    if not markers then
        markers = {}
    end
    return dumptable[type(value)](value, depth, markers)
end

function dump(value)
    print((dumpstr(value)))
end