What do I think about Lua after shipping a project with 60k lines of code?
134 comments
·April 17, 2025mabster
aomix
I saw someone describe python as “stressful” for this reason and I couldn’t agree more. It’s difficult to have confidence in any change I make or review. I need to sit down and manually exercise codepaths because I don’t get the guarantees I crave from the language or tooling. While with the small amount of Rust code I’ve written lately I could yolo changes into production with no stress.
pnathan
Agreed. I had to work in a larger Python codebase after spending a few years with Go and Rust and the drop in logical confidence around the language was remarkable.
I have, roughly, sworn off dynamic languages at this point. Although I have dreams of implementing a firm typed system over Common Lisp.
shermantanktop
Same, though my trauma was Ruby. Those Rubyists who were apparently born with the language spec in their heads can do amazing things, but I am a mere mortal who needs to be told I wrote bad code right when I wrote it, not told at 2am on a production server.
felipeccastro
I’m assuming that Python code base didn’t have thorough type hints. What if it had? Would Go still feel safer? I know these aren’t checked in runtime, but Python type system seems more thorough than Go’s, so shouldn’t a Python code base fully typed be even safer than Go? If so, why not?
(I know Python type checks aren’t mandatory, but for this question assume that the type checker is running in CI)
-__---____-ZXyw
Firm like:
https://coalton-lang.github.io/20211010-introducing-coalton/
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jlarocco
> I need to sit down and manually exercise codepaths
Isn't that exactly what unit tests are for?
pansa2
Yeah, that's a common argument for dynamic typing. You're writing tests anyway (right?), and those will catch type errors and many other kinds of error. Why bother with a separate level of checking just for type errors?
I personally believe it's a valid argument (others will disagree). IMO the main benefit of static types isn't for correctness (nor performance) - it's to force programmers to write a minimal level of documentation, and to support IDE features such as autocomplete and red underlines. Hence the popularity of Python type hints and TypeScript, which provide these features but don't fully prove correctness nor provide any performance benefit.
mkehrt
Fortunately my compiler writes a large number of unit tests for me, that run at compile time! I call it the "typechecker".
airstrike
Except now you're writing and maintaining twice the amount of code instead of relying on the compiler and/or type checker to help you catch those errors
d0mine
Do you believe that Rust's type system is as flexible, powerful, and easy to maintain as unit tests in Python?
MrJohz
One of the big advantages of Rust's type system is that, if you decide you want to change something (add a parameter, give a type a lifetime, rewrite an entire module), you can just do that, and then follow the errors until they're all gone. Often, once the types have been fixed again, the result will work first time when you try and run it.
In this regard, Rust (and other languages where lots of data invariants can be encoded in the type system) is very flexible and easy to maintain indeed, because you can easily make changes, even in very old or poorly-maintained code, without having to worry about the consequences. Moreover, rather than writing all the unit tests yourself, it's as if the compiler is writing the unit tests for you.
In fairness, you can't encode everything in the type system, so you still need unit tests in top of that, but in my experience you can get away with far fewer. In general, I would say that Rust's type system, when combined with unit tests, is far more flexible, powerful, and easy to maintain than dynamic Python with only unit tests.
12_throw_away
I write and test a lot of both rust and python, so I can say quite confidently:
1. Of course a type system is not as "flexible" as arbitrary test code.
2. Compiler-enforced type safety is many orders of magnitude easier to maintain than the equivalent unit tests
3. Defining rigorously enforced invariants with a type system is far, far more powerful than hoping you remembered to test all the important cases.
airstrike
No, it's more flexible, more powerful, and easier to maintain than unit tests in Python.
bormaj
If using python with type annotations, linters like ruff and mypy do a great job at identifying issues. It's no substitute for tests and nor will it give you the same guarantees that rust will at compile time. But I think it improves the base quality of the code.
mabster
The thing I find annoying with MyPt is trying to tell it I'm doing variable shadowing.
E.g. X is a list of strings Translate X to a list of indices Translate X back to a list of strings.
In that paragraph the input and output types are the same, but not complains about the second line.
I always have to introduce a variable with a new name.
je42
When using dynamic languages, either minimize code dependencies / function calls and complexity or ensure high test coverage.
kgeist
>This meant when we update a function signature we would often incorrectly update call sites, etc.
The same thing happened with our huge legacy PHP monolith, which was written before type hints were a thing. Developers were reluctant to refactor large chunks of code when the time came, because it was just too easy to introduce bugs - you couldn’t be confident about anything without manually digging through tons of code. So, when business requirements changed, they’d just bolt on some hacks to avoid touching the existing, tested code, and call it a day. It became a self-reinforcing loop: fear of refactoring → more hacks to avoid refactoring → more brittle code → even more fear of refactoring. Eventually, they added type hints and a linter to analyze them, but by that point you start to wonder - why are we even using a dynamic language and fighting its quirks?
shermantanktop
This is something I watch out for: teams which fear their own code and operate defensively, typically with cargo-cult practices that accumulate even though they themselves aren’t well understood.
mabster
When I started, the culture was already engineered to prevent this reluctance. You would hear "the code is fragile, it's going to break. Noone will shout at you for that." This was great. But I would prefer to just not have to "run in eggshells" haha!
z3t4
It can be solved with static analysis and type inference. Inference can be tricky though, as you have to backtrack and figure out what type of values functions return etc, so type hints/annotations make the job easier for the IDE/tooling developer, but they are not necessary!
arp242
> With dynamically typed languages I feel it's better to wait until you've tried to maintain the code for a while before you consider the languages effectiveness.
True for any language really. There's an entire category of blog posts: "I used language X for 2 weeks and here's my hot take". Okay, great. But what do you really know? For every language I've used for a serious amount of time I've changed opinion over time. Some things that seemed like neat ideas at the start turned out to be not so neat ideas down the line. Or things I considered pointless or even stupid at the start turned out to be very useful once I better understood the nuances and/or got used to working with it.
And of course it's double hard to judge will come back to haunt you a year down the line.
Even as an experienced programmer I find it hard to properly judge any of that from just a few weeks.
mabster
To extend on this: There was always this implied impression that the original developers were hot because they got stuff up and running really quickly and that all the newer developers were lukewarm because they weren't getting stuff happening quickly at all, all as a result of the original language choice!
szundi
This is what makes Java underrated these years. Some annoying stuff pays off over a decade several times. You can make insane complexity with ease.
ecshafer
Java is a great language, and the JVM a great platform. I think that the thing which makes Java underrated isn't the language, but rather Java Developers. There are tons of great Java developers, but they are probably great developers in any language. But Java being the language of choice at so many enterprises results in a large number of very low skilled and inadequate Java programmers, who would be bad developers in any language, but specialize in Java.
mabster
I have mixed feelings about Java. It's a solid feature set, and I really love how InterruptedException was always a thing, so you can generally terminate a thread and it works (a lot of languages don't do this right). I love checked exceptions.
But the spooky action at a distance type annotation hell, needing builders everywhere because of lack of named parameters, poorly conceived generics, nullability not being first class, lambdas being incompatible with checked exceptions, etc. are a pain.
TinkersW
Yeah I had a pretty high opinion of Lua when I first used it, then I came back to code I'd written years earlier, and the lack of types just made it a nightmare.
It really could use a fully statically typed layer that compiles down to Lua, and also fixes some of the stupid stuff such as 1 based indexing and lack of increment ops etc.
discreteevent
> It really could use a fully statically typed layer that compiles down to Lua.
That's Teal: https://github.com/teal-language/tl
packetlost
One of my coworkers described Python (specifically in reference to a niche framework, but I think it applies generally) as "a bucket of play-doh filled with broken glass"
greenavocado
Does said coworker use mypy?
packetlost
Yes. Mypy helps but isn't nearly enough, especially for a gradually typed codebase.
TJSomething
I think that much of game development is unlike a lot of other kinds of programming, where there's often more ad hoc game mechanic prototyping than maintenance. This is where dynamic programming excels. But of course, that consideration needs to be balanced against others.
mabster
My big Lua codebase was a gamedev codebase, haha!
teamonkey
They mention Luau near the end, and my opinion is that Luau is a significant improvement. Mainly because of the optional typing, but the other features too are each small but impactful quality of life improvements.
drysine
>when interfacing between C and Lua
Except for the indexing mismatch, I've found calling Lua from C and vise-verse very easy.
ksymph
So much lua stuff on HN the past few days, I love it.
Defold is a great engine. It has a somewhat steep learning curve (steeper than you'd expect, anyway) and its fair share of quirks, but more often than not the quirks are deliberate tradeoffs that steer you in the direction of structuring your game well. It really feels like an extension of the lua philosophy of giving you a narrow set slightly odd, but very robust and flexible tools that you build everything else out of.
I'm back to using LOVE2D for general tinkering but a few months with Defold really changed how I approach things. I've been meaning to write up a post about it. Either way though, I'd highly recommend checking out Defold to anyone interested.
nine_k
One big takeaway: a 60k LOC project in Lua is doable, and it will not crumble under its own weight.
Surprisingly, LuaJIT is not mentioned even once. Luau is mentioned, Teal is mentioned, Fennel, not. (But Haskell is mentioned!)
Little is told about the general code structure, likely because it's dictated by the (C++-based) game engine with Lua bindings. It would be interesting to see an analysis of a comparably large game built with Löve, for instance.
stevekemp
Years ago I wrote/maintained a modal console-based email client. It was written with some UI primitives in C++ and the UI actually maintained and controlled by lua.
Viewing a list of folders? Lua. Viewing a list of messages? lua. Viewing a single message? Lua. Those were the three main modes and UI options.
All the keybindings, layout, colour setup, and similar was dynamic. It actually worked out really well. For comparison I just ran "wc -l" against he codebase: 60k lines. Combination of C++ and Lua, but mostly Lua.
Having good scope and good tests made such a thing fine to support. Mostly the pain was broken MIME messages and handling dealing with the external world - e.g. invoking gpg to handle decryption and encryption.
I'd work with big-lua again if I had the need, it's a fun language and very flexible.
lifthrasiir
> it will not crumble under its own weight
It is possible to make it not crumble under its own weight, right? I had my share of Lua nightmare with more than 100K lines of code back when I was a gamedev [1], and it seems that there are some requirements in order to remain sane with the growth. Thankfully there are now multiple working type checkers for Lua, unlike when I had to built my own.
[1] https://news.ycombinator.com/item?id=18351788 is my canonical answer, but I have written many other comments about Lua which should be easy to search.
jerf
You can make anything, even assembler, not "crumble under its own weight" if you, the developer, bring enough discipline and care to it.
The main reason I like static languages and other such things is that after many decades of the programming community developing, since before I was born, we have not found very many best ways of "bringing enough discipline" to a codebase. It really all amounts to the same disciplines over and over. Check the types. Be sure guarantees are maintained. Document the input and output parameters. If there were dozens of very distinct and mutually-contradictory ways to impose this discipline, and there was no clear domination among those ways, then it might make sense for all of our languages to be loosey-goosey and not impose anything directly. But since we all generally find the same disciplines, we might as well pull those up to the language level and thereby enable them to be fully supported, and share the tooling among each other rather than expecting every junior dev to reinvent it from scratch... which they won't.
debugnik
> LuaJIT is not mentioned even once
Defold uses LuaJIT (except for web which I think uses Lua 5.1 compiled to wasm?), so it's taken for granted.
wruza
I read half the article and little is told in it in general. You'd expect some deeper developer reflections on a 60kloc project. Like, much deeper. The part about "spacer" hints that the second half won't surprise either. There's just not enough general xp to make conclusions.
null
tc4v
This dev seems really inexperienced and has weird uninformed takes. The "functional vibe" but it's just using boolean logic, the "reference in a table" bugs that would happen in any language but C, the ignorance of type annotations and so much time spend on problems caused by said ignorance...
kragen
He may not be super expert, but he doesn't pretend to be. His experience is still valid even if he doesn't really understand what functional programming is yet. (His example isn't just boolean logic.)
Being surprised by aliasing would have happened the same way in many languages, but not everything but C. It can happen in C too! But maybe in Python you would have used an (x, y) tuple and gotten an error from trying to mutate it, and certainly in Haskell or OCaml you wouldn't introduce mutability implicitly. In Tcl there's no way to get that problem in a list of lists, and in languages like Golang or Rust or C# you'd probably use an array of structs which would also be immune to aliasing. You could have the same problem, but it's less likely. I've known experienced programmers who were surprised by aliasing bugs, and even had trouble debugging them, maybe because they spent a lot of time in languages where they were possible but less likely.
What do you mean about ignorance of type annotations?
lolc
The example is not just boolean logic! In Lua logical ops, the last evaluated value is returned. The example makes use of that to assign something other than a bool. Not all languages do that. In Java for example, boolean logic always evaluates to a bool.
I'm not sure which part of that you missed, but maybe don't go too hard on calling others inexperienced based on your takes.
helsinki
Almost as many lines as my Neovim config.
xedrac
But not nearly as many as my Emacs config.
__MatrixMan__
Roughly 60k lines more than my Helix config.
para_parolu
How do you configure awesome plugins for helix then?
MrLeap
This made me laugh.
gnabgib
(2024) Discussion ~at the time (321 points, 260 comments) https://news.ycombinator.com/item?id=40538540
kragen
Heh:
> ...why Lua was designed this way. Dmitry told me that Lua was created at the Pontifical Catholic University of Rio de Janeiro and that it was acceptable for Pontifical Catholic Universities to design programming languages this way.
airstrike
Reads tongue in cheek but also to be clear, as a PUC-Rio alum I can say there's no such thing as a collective "pontifical catholic universities" board that determines how programming languages behave or how students and faculty should go about their businesses in a software engineering class...
pansa2
Are there any other programming languages designed by Pontifical Catholic Universities?
kragen
Almost certainly! The one here in Argentina has campuses in six cities and is well regarded, though it doesn't rank well in worldwide rankings. It has 24000 students at any given time, with alumni including the Queen of the Netherlands and one of the founders of OLX. It seems likely that the number of programming languages designed by one or another professor or student there at one time or another is in the dozens. One repo I found on GitHub uses a dialect of Smalltalk I'm not familiar with, but I don't know if it originates at the university: https://github.com/uca-argentina/2021-bigtalkers/blob/master...
The PUC in Santiago de Chile is even better, academically, and has some 34000 students at any given time.
It would be very surprising if different languages originating from these universities had significant design features in common!
suzzer99
Eight space tabs. My eyes! The goggles they do nothing!
jokoon
I am using godot, which uses gdscript, which is known to be a slow language.
But if your engine is already doing the heavy lifting, a slow scripting language will not matter, because it's not doing much.
Also gdscript is pretty nice to use, even if it's lacking tuples, unpacking and other things.
ludicrousdispla
Interesting article, although I am confused by the section referencing 'functional vibes' as the examples given just looks like standard code.
rahil627
good to see defold win. I prefer the love2D/dragonruby framework ways instead of engine now, but can’t deny defold has it all for 2D: game editor, common game structures provided modularly, deployment, no bloat. I could only wish it was the first engine I used. Life would’ve been so much better!
nirav72
This is the second game I've found out recently that is written in Lua. The first one one being - Beyond All Reason.
gavmor
Beyond All Reason is a SpringTA fork (hack? build?) like Zero-K? So the underlying engine isn't Lua, but higher level scripting is. I'm pretty sure this is fairly common, or was once.
Other games with Lua scripting: Roblox, Baldur's Gate, Civilization VI, Crysis, Factorio, World of Warcraft, Far Cry, Leadwerks, Friday Night Funkin', Foldit, Garry's Mod, Aquaria, Balanced Annihilation, Bitfighter, Bos Wars, Cataclysm, CivCity: Rome, Civilization: Beyond Earth, Company of Heroes, Cortex Command, Counter-Strike 2D, Crimson Steam Pirates, Dota 2, Dungeon Crawl: Stone Soup, Dungeons, Dungeons II, Dungeons III, Elven Legacy, Empire: Total War, Escape from Monkey Island, Eufloria, Exodus from the Earth, Angry Birds.
remram
Here they are:
gavmor
I can't recommend Zero-K enough. It plays like a dream. Super fun at all levels. Great 8v8 clashes of robots. Unbeatable price ($0). Great dev blogs.
gautamcgoel
Also Supreme Commander
scambier
Recently released, Moonring and Balatro are both written in Lua, and I think both with LÖVE.
msephton
YOYOZO, my game that received a "Best Games of 2023" accolade, was also written in Lua. It is only 39KB despite containing two music tracks, physics and particle systems, online high score board, dynamic sounds, two fonts, a tutorial and more. https://news.ycombinator.com/item?id=38372936
ecshafer
LOVE is a popular Lua game framework, so quite a few indie games are written in it.
daneel_w
Most of Heroes of Newerth's in-game logic is written in Lua.
ramesh31
>This is the second game I've found out recently that is written in Lua. The first one one being - Beyond All Reason.
Lua is traditionally the scripting language of choice for game development. It was absolutely ubiquitous in the industry before the days of Unreal/Unity. Famously, all of the WoW UI was Lua.
pansa2
Yeah, this presentation by Roberto Ierusalimschy (one of Lua's three authors) lists over 50 games that use Lua (slide #9):
fullstop
I am surprised that he did not include all of the Souls games, as they are hugely popular.
Oddly enough, I learned that they used Lua by reading the license information which came with the game. I don't remember if it was on the back of the box or in an paper insert, but it surprised me to see it included for some reason.
nvlled
Grim fandango too
With dynamically typed languages I feel it's better to wait until you've tried to maintain the code for a while before you consider the languages effectiveness.
I had to maintain a very large Lua codebase that has been active for several years. One big problem with Lua was how it will happily take more or less parameters to functions and continue to execute compared to something like Python where it is an error to pass the wrong parameters. This meant when we update a function signature we would often incorrectly update call sites, etc.
I can't remember the specifics but we had a few issues with tables being both dictionaries and lists. IIRC, if you delete a list index and there are later list indices, they will turn into dictionary keys. We had a few bugs to do with not traversing the entire array portion of a Lua table because of this.
I also implemented a few classic algorithms, e.g. bisect in Lua and you have to be very careful with 1-based indices. You also have to be very careful when interfacing between C and Lua. I prefer 0-based indices and [start, stop) style ranges for everything nowadays.
I much prefer statically typed code during maintenance. But dynamically typed languages like Python or Typescript where you can bolt on types, later if you wish, are not too bad.
Also using named parameters as much as possible is great for maintenance.