Configurable Lua table ANSI pretty printer/serializer. Public domain.

pretty_print_table.lua

local function pretty_print_table(tbl, file, indent, num_fmt, no_ansi, style, seen)
	-- default parameters
	file = file or io.stdout
	indent = indent or 0
	num_fmt = tbl.__print_table_number_format or num_fmt or "%.2f"
	style = tbl.__print_table_colors or style or {}
	seen = seen or {}

	-- calculate ANSI color codes
	local key_code = no_ansi and "" or style.key or "\027[1;36m"
	local tbl_code = no_ansi and "" or style.tbl or "\027[35m"
	local comt_code = no_ansi and "" or style.comt or "\027[33m"
	local str_code = no_ansi and "" or style.str or "\027[32m"
	local num_code = no_ansi and "" or style.num or "\027[34m"
	local func_code = no_ansi and "" or style.func or "\027[91m"
	local bool_on_code = no_ansi and "" or style.bool_on or "\027[92m"
	local bool_off_code = no_ansi and "" or style.bool_off or "\027[91m"
	local reset_code = no_ansi and "" or style.reset or "\027[0m"

	-- from key-value hash format to list of {k,v} tuples
	local itbl = {}
	for k, v in pairs(tbl) do
		table.insert(itbl, { k, v })
	end

	-- sort list of tuples by keys
	table.sort(itbl, function(a,b)
		if type(a[1]) == "number" and type(b[1]) == "number" then
			return a[1] < b[1]
		else
			return tostring(a[1]) < tostring(b[1])
		end
	end)

	-- iterate over tuples, print recursively using ANSI escape sequences for colors
	local id = (style.indent_chars or "\t"):rep(indent)
	for i,t in ipairs(itbl) do
		local k,v = unpack(t)
		local ls = (i==#itbl) and "" or ","
		local ke = tostring(k) .. " = "
		if type(k) == "string" and (("%q"):format(k) ~= "\""..k.."\"") then
			ke = ("[%q] = "):format(k):gsub("\\\n", "\\n")
		elseif (type(k)=="number") and (k==i) then
			ke = ""
		elseif type(k)=="number" then
			ke = "[" .. num_code .. k .. reset_code .. key_code .. "] = "
		end
	    file:write(id .. key_code .. ke .. reset_code)
	    if type(v) == "table" then 
			if seen[v] then
				file:write(tbl_code .. "{}" .. ls .. comt_code .. " -- repeat: <" .. tostring(v) .. ">" ..reset_code .. "\n")
			else
				seen[v] = true
				file:write(tbl_code .. "{ " .. comt_code .. "-- <" .. tostring(v) .. ">" .. reset_code .. "\n")
				print_table(v, file, indent+1, num_fmt, no_ansi, style, seen)
				file:write(id .. tbl_code .. "}" .. reset_code .. ls .. "\n")
			end
		elseif type(v) == "string" then
			file:write(str_code .. ("%q"):format(v):gsub("\\\n", "\\n") .. reset_code .. ls .. "\n")
		elseif type(v) == "function" then
			file:write(func_code .. "nil" .. ls .. " -- <" .. tostring(v) .. ">" .. reset_code .. "\n")
		elseif type(v) == "number" then
			file:write(num_code .. num_fmt:format(v) .. reset_code .. ls .. "\n")
		elseif type(v) == "boolean" then
			file:write((v and (bool_on_code .. "true") or (bool_off_code .. "false")) .. reset_code .. ls .. "\n")
		else
	        file:write(tostring(v) .. ls .. "\n")
	    end
	end
end

local t = {"foo", "bar"}
local test = {
	"First",
	"Second",
	"Third",
	44,55,66,
	[222] = "is 222",
	[999] = "Almost 1000",
	["Hello\nWorld!"] = "Foo Bar!",
	[false] = true,
	print = print,
	hex = {
		__print_table_number_format = "0x%.1x",
		[0]=0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
	},
	colors = {
		__print_table_colors = { str = "\027[91m" },
		red_str = "This string is red!"
	},
	t_copy_a = t,
	t_copy_b = t,
}
print_table(test)