4/22/2026 at 10:06:24 AM
Function colouring, deadlocks, silent exception swallowing, &c aren’t introduced by the higher levels, they are present in the earlier techniques too.by joelwilliamson
4/22/2026 at 10:26:43 AM
Function coloring also only applies to a few select languages. If your runtime allows you can call an async function from a sync function by pausing execution of the current function/thread whenever you're waiting for some async op.Libraries like Tokio (mentioned in the article) have support for this built-in. Goroutines sidestep the issue completely. C# Tasks are batteries included in that regard. In fact function colors aren't an issue in most languages that have async/await. JavaScript is the odd one out, mostly due to being single-threaded. Can't really be made to work in a clean way in existing JS engines.
by chmod775
4/22/2026 at 12:50:01 PM
“Function coloring” is an imaginary issue in the first place. Or rather it's a real phenomenon, but absolutely not limited to async and people don't seem to care about it at all except when talking about async.Take Rust: you return `Result<T,E>`, you are coloring your function the same way as you are when using `async`. Same for Option. Errors as return values in Go: again, function coloring.
One of your nested function starts taking a "serverUrl" input parameter instead of reading an environment variable: you've colored your function and you now need to color the entire call stack (taking the url parameter themselves).
All of them are exactly as annoying, as you need to rewrite the entire call stack's function signature to accommodate for the change, but somehow people obsess about async in particular as if it was something special.
It's not special, it's just the reflection that something can either be explicit and require changing many function signatures at once when making a change, or be implicit (with threads, exceptions or global variables) which is less work, but less explicit in the code.
by littlestymaar
4/22/2026 at 12:38:17 PM
I wish the “Function coloring” died. It made sense in the context of the original blog post (which was about callback hell), but doesn't make sense in the context of async/await. There's litterally nothing special with async, it's just an effect among many others.As soon as you start using function arguments instead of using a global variable, you are coloring your function in the exact same way. Yet I don't think anyone would make the case that we should stop using function arguments and use global variables instead…
by littlestymaar