What color is your function? (2015)

I really don't like this article. It has a catchy, profound-sounding title that people bandy about to argue against stuff they don't like.

All functions, even non-async functions, are colored. In any large system codebase you'll have functions that can only be called in certain situations, with the right setup, whatever, and if you're lucky this is communicated by types but regardless those restrictions can't be avoided. It's easy to call low-restriction functions from high-restriction ones and not the other way around.

Furthermore, it's not like the alternative to explicit await doesn't have issues too (that the article doesn't mention). There is inherent complexity, it's a tradeoff, you can't just syntax it away.

> You still can’t call a function that returns a future from synchronous code. (Well, you can, but if you do, the person who later maintains your code will invent a time machine, travel back in time to the moment that you did this and stab you in the face with a #2 pencil.)

Author makes up a lie.

Then lampshades it away with a colorful non sequitur.

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The alternatives that people praise like golang, have other tradeoffs that are much worse because the async logic is now implicit. Your entire codebase is now a surface area that is at risk of being blocked by waiting on a channel; the the mitigation of this is through responsible use of coroutines, but then you're right back around to extra information about your code that is analogous to colring, except not as explicit as async/await.

Go doesn't have colored functions due to its nice fat runtime hiding all the async magic away for us.

That makes it a pleasure to code concurrent stuff for IMHO.

It does have its own similar problems though - does a function return an error? If so you are going to need to plumb the error return through all the callers. Does a function need a context.Context? Ditto.

I guess you can't win them all :-)

I wish the key word was instead dontawait and was used inversely to how await is used. 99% of the time I'm using an async function, despite however slow it is, there's nothing for my code to do but wait for it to finish. But if for some reason I would like the next line of code to run before the current one is done, I'll let you know.

Like, why can't my sync function await something asynchronous? If it has to lock up the whole thread while that function executes, that's fine because that's how it was going to work anyway 99% of the time

We need algebraic effects in more languages, this solves the function coloring problem. OCaml 5 has them and it seems to be doing quite well, combine that with the semantics of the borrow checker in the form of OxCaml and we might just have an ideal language. I'd like to see algebraic effects in Rust as well but sadly it seems their keyword generics initiative is languishing.

Related, one of the former React maintainers wrote a primer on algebraic effects that's a good read: https://overreacted.io/algebraic-effects-for-the-rest-of-us/

Colored functions are good. It reflects the language design on signaling what is important, and what are the properties it want the writer to pay attention. Other examples of colored functions:

* Haskell: pure function and non-pure (IO monads) looks different. * Rust: unsafe functions (or block) requires special markers.

> Spidermouth the Night Clown

Thanks for my next horror shortfilm plot. Twist: he's the protagonist

My first ever EM showed me this piece ~10 years ago, and I still think about it a lot. One pattern I've adopted is to keep as much code to be synchronous as possible. On larger teams, especially when the slop-cannon is really going, I can at least depend on codeowners to tag me if someone tries to convert something to async (eg. adding a DB call somewhere), because they chain of things that need to be converted to async is so long. Then I can jump in and say "this entire chain of code is sync, if you want a DB call, do it somewhere else"

Purple.