> I also don't like how async/await ends up taking over a whole codebase. Often making one function async will cause you to update other functions to be async so you can do proper awaiting.
This is basically the function coloring problem. There was some ardent discussion about this a few weeks ago on HN [1], where the top comment positioned function coloring as a feature, because it highlights where expensive operations like IO might potentially be happening in your application.
I saw a comment recently where someone pointed out an old API in Java where comparing two URLs for equality initiates a DNS request, and so something as simple as putting a URL in a hash table could end up involving a network request [2]. So maybe it's reasonable to color functions that connect to the network at the very least. If I used a URL comparison library and it returned a promise it would immediately set off alarms in my mind.