fun fact: clojurescript had support for asynchronous paradigm through core.async library (CSP style) long before async/await landed in javascript itself.
edit: i'm in no way trying to diminish the value of this release, just pointing out how cool it is that you can get new language features before they are available in the host language by just adding a library to your dependencies. clojure is awesome!
> fun fact: clojurescript had support for asynchronous paradigm through core.async library (CSP style) long before async/await landed in javascript itself.
Definitely. I was heavily using it and it worked: a few quirks but we did have async/await since more than a decade. I think I discovered it after watching a talk by David Nolen.
Since then I moved to minimal JavaScript on the front-end: SSE is one-way and that is beautiful. I'm glad to see many devs, from a great many different languages, now getting interested in SSE.
Here's a great, recent, talk by David Nolen called "A ClojureScript Survival Kit":
https://youtu.be/BeE00vGC36E
I cannot thanks David "Swannodette" Nolen enough for all the work he did on ClojureScript (and core.async) since its inception. And what's amazing in this talk is that he's actually excited at the idea that we may do away with ClojureScript and use pure Clojure (on the server-side) and server-side events, with just a tiny of JavaScript.
The real demo starts around 26:30. He shows a Webapp running on the client and how much resources it's using, then he shows the exact same Webapp running on the server and pushed one-way to the client using SSE. It is wild: resources usage drops to near zero.
YMMV but I find it easier to reason about my webapps and manage state now that I'm using a minimal DOM morphing lib: I used to have two REPLs (one for Clojure, one for ClojureScript) and lots of back-and-forth traffic and hard-to-track / reproduce state. Now everything is definitely snappier and way easier to reproduce.
I'm not saying SSE is going to work in every case though: YMMV. But in any case the video or at the very least the demo starting @ 26:30 is very much worth watching.
thanks for the link, i was just recently trying to find that talk!
re server-side rendered fragments - htmx is extremely easy to integrate with your clojure(script) projects, i found it to be quite pleasant paradigm, but i have no skin in the game so take it with grain of salt xD
True, but there are many reasons to avoid core.async, especially in 2026.
It balloons up the Js artifact, has no inherent error model, and transforms into state machine code that's hard to read/debug if something goes wrong. Plus, the `go` macro encourages overly-large functions, because it can't transform code outside its own sexpr.
As one Cognitect put it, "core.async is beautiful nonsense".
> has no inherent error model
I'll pitch in here, as I've been doing a lot of thinking about this issue and ended up writing my own (tiny) tools for handling anomalies, modeled on the very well thought-out https://github.com/cognitect-labs/anomalies categorization.
This is actually a much wider problem and not specific to core.async. Handling anomalies is difficult. It used to be that you would have exceptions and errors which would be thrown, unwinding the stack. This pattern no longer works in asynchronous code, or code that needs to pass anomalies between the server and the client. In practical applications, an anomaly might need to be returned from a function, passed through a `core.async` channel, then thrown, unwinding the stack on the server side, then caught and passed to the client side over a WebSocket, and then displayed to the user there.
Solving this well is not easy. I think my toolkit, iterated and improved over the years, is close to what I need. But I'm pretty sure it wouldn't handle all the real-world use cases yet.
But again, this is not specific to core.async in any way.
What is your opinion on farolero[0]?
[0]: https://github.com/IGJoshua/farolero
At a first glance, it does much more than what I would want to.
My status toolkit just extends the Cognitect anomalies to be statuses, adding ::failed (parameters correct, but could not perform request), ::ok, ::accepted and ::in-progress. It also adds a bunch of utility functions like status/?! (throws the parameter if it's anomaly, returns the parameter otherwise) and macros like status/-?> (threads if an expression is not an anomaly). That's it.
I deliberately avoid trying to do too much here.
For me it also lacks observability. It has been a few years since I last used Clojure, but I found manifold to be a much better fit for actual production code that you want to optimize.
I loved ztellman’s “everything must flow” talk on the topic.
Heh, I used to maintain manifold/aleph for a few years after Zach left the Clojure community.
And here I thought I was too dumb to grok core.async all those years ago (ps I still am)