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Rewrite Bun in Rust has been merged

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Re: Rewrite Bun in Rust has been merged

#361

Post by carllerche »

konart wrote: post #267
alfanick wrote: post #260

I'm confused. Never heard of Bun until a few days ago here on HN. It's some nodejs wrapper thingy, written in Zig, and someone decided to use LLM to rewrite it in Rust. Is this a big deal? Who is even using this software? Why is this big?

Rust vs Zig "wars" etc. Also at some point Bun was acquired by Anthropic. And some people feared that this will greatly influence Bun's development.

I don't think Rust vs. Zig has anything to do with why people are talking about this. It is a large piece of "real software" that underwent a full language transition in ~1 week using LLMs. That is a big deal regardless of the language and will be a case study regardless of how it turns out.

Re: Rewrite Bun in Rust has been merged

#362

Post by onlyrealcuzzo »

Aurornis wrote: post #333
vitaminCPP wrote: post #253

> +1009257 -4024 Bun is now over 1M lines of Rust code. This is approaching the size of the Rust compiler itself; except that BunJs is mostly a JavaScript interpreter wrapper + a reimplementation of the NodeJS library (Rust STD wrapper). I think BunJS is becoming the canary for software complexity management in the LLM era.

The Bun codebase had a similar number of lines of code before the rewrite. There's nothing unusual about a rewrite coming in with a similar LOC number.

I was going to comment this same thing.

I don't know enough about what Bun does... But Rust is so insanely complicated, it's hard for me to wrap my head around how Bun is equally complictated.

Re: Rewrite Bun in Rust has been merged

#364

Post by Daishiman »

Barrin92 wrote: post #344
petcat wrote: post #308

Earlier quoted context omitted.

Cool you can just search specifically for potentially unsafe code in Rust. How do you search for unsafe code in Zig? Or do you just have to assume it's everywhere?

if half of your files in a million line codebase are unsafe that doesn't tell you much any more. Presumably the point of a Rust rewrite is that you actually make use of Rust's safety features in a coherent way. But given the whole "let AI rewrite this for me" stunt nature of this project that was not going to happen because that would require well, actual thinking and a re-design. So now you have Zig disguised as Rus…

And? This is absolutely the correct and standardized way to do mechanical rewrites: you do a rewrite that maps directly to the original source so you can rely on the original correctness guarantees and bug-for-bug compatibility and log issues, and then you go into the next phase where you begin to use idiomatic constructs.

This is the same in COBOL-to-Java ports that have been done in banking and insurance for the past 20 years.

Re: Rewrite Bun in Rust has been merged

#365

Post by davidatbu »

debugnik wrote: post #355
bhaak wrote: post #335

Earlier quoted context omitted.

It passed all the tests. If you can't trust your test suite to catch an automatic language translation you shouldn't trust it at all. :)

It also modified many of the tests to make them pass in mischievous ways. You can't trust a test suite to catch regressions if the new version doesn't use the same test suite.

Do you have some examples?

Re: Rewrite Bun in Rust has been merged

#366

Post by randusername »

dgellow wrote: post #324

If the bun team is around I would be interested to get their opinion on this: in the old time migrating a 1M codebase from one language to another meant you would pretty much become an expert in the target language. The output of the work is team experience/knowledge + the actual rewrite. With that Bun rewrite do you feel that the Bun team learned something other than “Claude can rewrite a very large codebase in no t…

I used to think software was inherently valuable.

Then I decided that software is of limited value without a team to maintain it. Not necessarily because they fix it, but because they represent a bunch of humans who collectively understand it and therefore give it more possibilities.

And now this. I'm not sure what to make of it.

Re: Rewrite Bun in Rust has been merged

#367

Post by Philpax »

szmarczak wrote: post #165
4b11b4 wrote: post #147

Earlier quoted context omitted.

Same, just gonna stick with node. On the other hand, the trial by fire will be interesting to see... long term I can only imagine the kinks will surely work themselves out

Wait till you hear about https://github.com/nodejs/node/pull/61478

I don't understand the point you're trying to make here.

Re: Rewrite Bun in Rust has been merged

#368

Post by sesm »

When announcements say that rewrite took 1 week, I wonder how much time went into preparing this file with very detailed instructions on mapping Zig to Rust idioms: https://github.com/oven-sh/bun/commit/46d3bc29f270fa881dd573...

On top of that, if you look at 'Pointers & ownership' and 'Collections' sections, the Bun codebase is already prepared, using internal smart pointer types that map 1-to-1 to Rust equivalents, and `bun_collections` Rust crate already exists.

This makes an impression, that rewrite was prepared long time ago and was Bun team proposition to Anthropic during the acquisition deal.

Re: Rewrite Bun in Rust has been merged

#369

Post by GeekyBear »

sunrunner wrote: post #306
vitaminCPP wrote: post #253

> +1009257 -4024 Bun is now over 1M lines of Rust code. This is approaching the size of the Rust compiler itself; except that BunJs is mostly a JavaScript interpreter wrapper + a reimplementation of the NodeJS library (Rust STD wrapper). I think BunJS is becoming the canary for software complexity management in the LLM era.

I'm not sure if it's just the leading '+' or if there are other factors for phone number detection on iOS, but on mobile the line count changes are underlined and I can tap it to start a call, which, if it is because of the diff size, is something I find pretty amusing.

Apple has had a feature called Apple Data Detectors since the 90's that looks for different patterns in text and allows you to perform actions on them.

So if the text includes a phone number, email address, flight number, package tracking number, street address or other pattern in the data it is underlined and allows you to perform one or more actions.

The patterns it looks for and actions it takes are extensible by developers.

If you don't care for it, you can turn it off.

Re: Rewrite Bun in Rust has been merged

#370

Post by famouswaffles »

Barrin92 wrote: post #344
petcat wrote: post #308

Earlier quoted context omitted.

Cool you can just search specifically for potentially unsafe code in Rust. How do you search for unsafe code in Zig? Or do you just have to assume it's everywhere?

if half of your files in a million line codebase are unsafe that doesn't tell you much any more. Presumably the point of a Rust rewrite is that you actually make use of Rust's safety features in a coherent way. But given the whole "let AI rewrite this for me" stunt nature of this project that was not going to happen because that would require well, actual thinking and a re-design. So now you have Zig disguised as Rus…

>if half of your files in a million line codebase are unsafe that doesn't tell you much any more.

If half of your files in the first pass of a million line rewrite are unsafe then that's completely fine. Do you understand what the tag actually is? It doesn't even mean that the code is actually unsafe, just that the compiler can't guarantee its safety, which can happen for a number of reasons, some benign.

Who rewrites a 700K codebase trying to be idiomatic from the get go ? That's setting yourself up for failure, whether you're a human or a machine.

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