(sometimes AI explains it better)

Created	Updated	Size	License
2017-05	2026-08-31	< 60 K	LGPL3

What

Function to serialize data in Lua table to string with Lua code that recreates this data.

Lua tables can contain cross-references, so actually it's graph encoder to Lua source code.

Scope

Primary objective is serialization graph to source code. Nice output is secondary objective.

First run

t2s = require('serialize_lua_graph')
print(t2s(_G))

Encoding options

Encoding options is optional table that can be passed as second argument.

Serializer function supports three encoding styles: minimal, readable_short and readable_long. Encoding style governs whitespaces and determines general text layout. Style lives in style string field.

Serializer function supports three behavior flags: use_compact_indices, use_compact_sequences and omit_tail_delimiter. Behavior flags govern optional lexical elements emission. They determine what syntax elements will be present. Behavior flags are boolean fields.

Example:

local g2s = require('serialize_lua_graph')
local Options = { style = 'readable_short', use_compact_sequences = false }
local str = g2s(_G, Options)
print(str)

We'll demonstrate their effects on excerpt of _G table printout.

Style	Output
minimal	local T_1={};local T_2={};
readable_short	local T_1 = { };
	local T_2 = { };
readable_long	local T_4 = {
	huge = 1/0,
	maxinteger = 9223372036854775807,

Behavior flag	Output	Value
use_compact_indices	['coroutine'] = T_1,	☐
	coroutine = T_1,	☑
use_compact_sequences	[1] = 'nil',	☐
	'nil',	☑
omit_tail_delimiter	['utf8'] = T_8, };	☐
	['utf8'] = T_8 };	☑

Details/limitations

• It does not distinguish between -NaN and NaN

  Our check for NaN is n ~= n.

  So both -(0/0) and 0/0 are serialized to string 0/0.

  From our point of view concept "this is not a number, but negative" is gibberish.

• You can hit limit of Lua local's

  For common subtables we emit something like local T_2 = {.

  Lua implementations have limit on number of locals near 200.

  So when number of common subtables is over 200 your Lua interpreter won't be able to load code.

  We think it's not our problem. From our point of view we're exporting statement with value capture.

• Functions, threads, userdata and metatables are not serialized

  First, it makes no practical sense to serialize functions.

  C functions can't be serialized.

  For Lua functions you can store their bytecode. But its instructions may use upvalues. We see no practical sense in trouble of retrieving upvalues (which may end up to something unserializeable).

  Second, threads (coroutines) and userdata are not serializeable.

  Third, metatables.

  Our common pattern is that metatables contain functions. Not serializeable.

  Even if in your case they contain plain strings/tables we see no practical need in tracking links between base table and metatable and adding AST node to emit setmetatable.

Requirements

• Lua 5.3 (or 5.4, 5.5)

Install/remove

• Save file serialize_lua_graph.lua from deploy/
• Place it to your Lua workplace for require()

Modify

• Clone repo
• Modify files in src/

Rebuild

• Clone workshop repo
• Checkout it to date near "Updated" date from stats plate (at header of this Readme)
• Modify package.path in builder/create_deploy.lua so it can find your cloned workshop repo
• Run builder/rebuild.sh

See also

• Ser -- Beautiful trickster-style implementation of same thing by Jasmijn Wellner

  We've overgrown obsession with regexps and strings long ago. Still it's very nice example of that style. Ten times less code!

• workshop -- My personal Lua framework on which this tool is based

• My other projects