[xpe]

> So on the title, I picked this because it's simply the truth. Since async landed in 2019 or so, not much has changed.

Hi. The article calls Rust async an MVP. You should expect strong reactions when you frame it like that.

"MVP" has a generally understood meaning; distorting that is unhelpful and confusing. Rust's async was not an MVP when it was released in 2019. It was the result of a lot of earlier work.

Rust async: (a) works well for a lot of people and orgs in production settings and (b) is arguably better designed than most (all?) other async implementations. Calling it an MVP is far from "simply the truth". It is an opinion -- and frankly a pretty clickbaity one. I appreciate your article's attention to detail, but the title is straight up shameful sensationalism.

I strive to not reflexively defend the status quo, but I get really chafed when people conveniently blur the difference between fact and opinion.

Please argue on narrowest correct claims available. The current title overstates your claims and undermines its overall credibility. Your central claim (as I read it) is that for embedded software there are opportunities for async improvement in Rust. Yeah this might sound boring, but I think it's accurate.

My other main criticism of your article is when it claims Rust async breaks the "zero cost abstraction" principle. I don't buy this claim, because you do not show that hand rolling the code provides the same guarantees. A lot of people misunderstand what "zero cost" means; your article wouldn't be the first to give the wrong impression.

Writing is hard (different audiences bring different backgrounds), and I commend anyone who puts their ideas out into the world. Please take this as constructive feedback: please agree or disagree with me on the merits. Ask and engage where I'm unclear.

[steveklabnik]

> Rust's async was not an MVP when it was released in 2019

The team literally described it as such.

One of the main architects of Rust’s async/await, withoutboats, left a comment on lobsters:

> It's just the truth. Neither in the language design nor in the compiler implementation has hardly any progress been made in the now 7 years since we shipped the MVP. The people primarily involved in delivering the MVP all become less active in the project around the same time and delivery since then has stalled out.

>

> I hope this person receives the support to do this work.

Rust’s async is great, and I feel you around some of the less informed criticisms. But it’s been called an MVP for a decade now, it’s not an insulting characterization. Just because it’s been an MVP does not mean it’s not good or useful.

[surajrmal]

Arguably the state it was left in is the state that was sufficient for the needs of all adopters. Don't fix something if it ain't broke. I know it's been sufficient for fuchsia which did a lot of the initial investment. The types of improvements described in the post tend to only matter at scale or in embedded use cases. No one from those realms has decided it was a sufficiently important problem to prioritize solving until now so it didn't get solved.

Even if MVP is the correct term for its current state, it has a connotation to it which less informed folks will take away the wrong meaning from, so perhaps it's not useful to continue to propagate it even if true.

[steveklabnik]

> No one from those realms has decided it was a sufficiently important problem to prioritize solving until now so it didn't get solved.

This is both true and not true. It's no secret that the async ecosystem has had deep social rifts for a very long time, and that's made it very tough to actually make progress by anyone, regardless of the desire to.

It is true that async massively gave a boost to Rust's adoption, and it is good enough for many users. It is a monumental technical achievement. At the same time, that doesn't mean it's perfect.

[xpe]

Sorry, I was too harsh. Or to be more precise: I should not have directed my criticism only at this particular blog post. This topic is a hot mess. Yes, even the 2019 blog post announcing Async Rust [1] used the phrase:

> On this coming Thursday, November 7, async-await syntax hits stable Rust, as part of the 1.39.0 release. This work has been a long time in development -- the key ideas for zero-cost futures, for example, were first proposed by Aaron Turon and Alex Crichton in 2016! -- and we are very proud of the end result. We believe that Async I/O is going to be an increasingly important part of Rust's story.

> While this first release of "async-await" is a momentous event, it's also only the beginning. The current support for async-await marks a kind of "Minimum Viable Product" (MVP). We expect to be polishing, improving, and extending it for some time.

> Already, in the time since async-await hit beta, we've made a lot of great progress, including making some key diagnostic improvements that help to make async-await errors far more approachable. To get involved in that work, check out the Async Foundations Working Group; if nothing else, you can help us by filing bugs about polish issues or by nominating those bugs that are bothering you the most, to help direct our efforts.

---

MVP originated from the lean startup world: the core meaning is to build the smallest thing that validates demand. Async-await (a-a) was so much more than that.

Whoever wrote the blog post wrote "MVP" which leaves a reader wondering: are those scare quotes? [2]

Nice a-a was "in the air" since Go shipped it in 2009. Compiled state machines hit the scene not long after: C# in 2012, Clojure in 2013. So demand did not need validation. As I understand it, probably the biggest driver for Rust a-a was to provide a common foundation for work going forward.

The effort and thinking that went into async/await probably blows away 99.9% of MVPs released out into the world! And I don't think it would be crazy to say Rust's a-a was better than ~80% of even "1.0" products.

I don't want to get bogged down in mere definitions... I'm emphasizing the primary emotional vibe. Using MVP (or "MVP") is a surefire way to conjure the wrong emotional valence. It invites confusion and downplays years of incredible work.

My feeling is that original blog post used that framing because the Rust team is famously open to taking however much time is needed to get things as close to perfect as they know how.

[1]: https://blog.rust-lang.org/2019/11/07/Async-await-stable/

[2]: https://en.wikipedia.org/wiki/Scare_quotes