Benoit Daloze of TruffleRuby points out that this is all much easier to read if you define your Ruby internals in Ruby, like they do. He's not wrong.

It might be worth moving the latest updates to the top of this answer. I had to go through the whole thing to get to the best answer, flexbox.

Svelte looks pretty similar, but has two small changes that personally make the Svelte code easier to read, in my opinion:

It is much easier to track what is going on within the activity. Instead of transporting additional state via ctx, you expose the outcome via an additional end event.

So why the over-complication? What we got now is replicating a chain of && in the former version. This time, however, you will know which condition failed and what went in by using tracing. Look at the trace above - it’s impossible to not understand what was going on.

“Make it right” means that the code is maintainable and easy to change. Humans can read it, not just computers. New engineers can easily add functionality to the code. When there’s a defect, it is easy to isolate and correct.