Code generation is very common at Meta. One just needs to create a query or fragment. A fragment can be spread at the root query level using relay so it will do the fetch once. It gets more complex because you can lazily query more data based on parameters you pass into GQL. It feels like magic and is really annoying imo.
I don't know about on-HackerNews but there's a discussion about their "all of Facebook optimizing compiler" infrastructure from when they did the site redesign in 2020: https://engineering.fb.com/2020/05/08/web/facebook-redesign/...
> perhaps not coincidentally, React introduced "server actions" as a mechanism that is very similar to [the above]
Yep - there's also the Scala framework LiftWeb (https://www.liftweb.net/), the Elixir framework Phoenix (https://www.phoenixframework.org/) and of course the system we're using right now (Arc) that do similar things. Scaling these kinds of UUID-addressed-closures is harder (because the client sessions have to be sticky unless you can serialize closures and send them across the network between servers).