[kikimora]

Bun never was great in terms of stability. It has been vibe coded for 6 month but code was reviewed by a person.

>It already has been proven that LLM's can maintain such codebases.

Proven is a strong word. In my experience AI fails miserably at anything beyond junior level tasks. We will see soon, once bun goes into production.

[esperent]

> Bun never was great in terms of stability

It's very easy to throw shade like this on software if you've got a bugbear with it. I'm sure you can even come up with a bunch of these "stability" problems when challenged on it. I know I could, for basically any large piece of software that I've ever used.

But really, is bun worse in this regard than any other similarly ambitious open source software within it's first few years?

[conartist6]

see that's fine with me if they want to take a year or two of human time and do the rewrite properly

this is a piece of software with no architecture, and whose owners have no regard or respect for architecture. I can virtually guarantee that on average every bug they fix will create one new bug, because that's what it's like to work on software with no intentional architecture

[brabel]

What are you talking about?? Bun in Rust is a port, almost exactly the same code base on a different syntax. The architecture did not change at all. Amazing how people comment without even knowing what they are talking about.

[thayne]

Zig and Rust are significantly different languages. If bun has a good architecture in zig (which I don't know if it does or not), that doesn't necessarily mean it had a good architecture for rust. A direct translation of zig code would probably result in pretty unusual rust code, and probably a lot more unsafe usage than if it had been originally written in rust.

[adampunk]

I don’t really understand this objection. For every tool that I use, am I supposed to divine the best underlying language for it and then determine whether or not it is written in that language? Don’t I have better things to do?

[kikimora]

Because of borrow checker you would build data structures differently in Rust compared to Zig. Automated translation simply maps Zig constructs onto unsafe Rust code. I have no idea how feasible it is to go from totally unique way of using Rust to mimic Zig to idiomatic Rust.

[thayne]

I'm not saying that bun shouldn't be written in rust. I'm saying that since it was originally written in zig, there were undoubtedly architecture and design decisions that were made that made sense in zig, but not so much in rust. When rewriting something in a different language, especially one significantly different than the original it is common to need to re-architect some things, and mechanically translating line by line from one language is probably going to result in some low quality code, even if the original was decent.

I think that using AI to translate bun from zig to rust might produce a good starting point. But it was done one file at a time, with minimal human review, and I'm skeptical that the result is quality maintainable code.

[fragmede]

What is that tool in relation to the rest of your workshop though? If it's a simple hammer that you can swap out for $20 and you only use it once a month, who cares what kind of metal it's made out of, as long as it works. But if the $6,000 4-axis CNC machine that's at the heart of your machine shop and every minute of downtime on it costs you money, if it's starting to rust, no, you don't have better things to do than to look into what it's made of.

[soraminazuki]

Very amazing indeed. Here you are making bold assumptions about a huge pile of code not a single human being has ever read in any meaningful amount.

[brabel]

The only assumption you need to make is how the process went about, which was described by Jarred on a HN comment when the PR was first discussed: they had prompt that described exactly how things should be translated, for each "pattern" they were using in Zig, an appropriate equivalent was described in Rust. Zig and Rust are not that different, both are system languages and things can be done similarly in both languages, so architecture-wise I would think the exact same thing would work fine. I am not sure whether the LLM actually wrote a transpiler which just followed the rules, or if it did the job itself, since that information is not public yet, as far as I know, but my guess is that the LLM wrote a transpiler to do the job, then reviewed/fixed compilation issues, then fixed tests. And I'm pretty sure some human interaction was part of that as well.

[kikimora]

>The only assumption you need to make is how the process went about, which was described by Jarred

This is not how the process went. This is how Jarred thinks it went, a huge difference.

>my guess is that the LLM wrote a transpiler to do the job

My guess is different. I think one agent translated code, another compiled it, feeding errors back into translator to fix. Then last agent modifies code to fix tests. All governed by a set of md files.

[soraminazuki]

So now you've gone from making assumptions to making up wild stories territory. Well, the commit granularity isn't that of transpiler passes, and more importantly, it's completely irrelevant to how the majority of the code hasn't even been read by anyone.

[kikimora]

Nobody reviewed resulting code. Maybe all tests are empty and this is why they pass. Maybe tests were modified to pass because this is the only thing LLM could do to make them pass. Maybe it hallucinated something in the process. We have no idea.

[jsnell]

We do have an idea, and it contradicts your guess: https://news.ycombinator.com/item?id=48133806

[kikimora]

You suggest there is only JS tests that do not need a rewrite? This is crazier than I thought…

I took tests as an example. There are so many other things that can go wrong. Rust and Zig standard libraries may have different semantics not picked up by AI. Like one guarantees insertion order of a dictionary and other does not. Differences in how runtimes react to Linux signals, how they do file IO, etc.

If I were a Bun user I would be moving off from bun unless it has excellent test coverage (which I think it does not). During a normal release cycle I offered a small increment of functionality with small number of issues. Here I’ve been offered a complete rewrite, potentially having thousands of issues. I don’t want to be a guinea pig in this experiment.

I’m genuine curious how this will unfold.