The .map() callback receives as its input an RpcPromise, not the actual value. You can't do any computation (including branching) on an RpcPromise, the only thing you can do is pipeline on it. Since the map callback must be synchronous, you can't await the promise either.

So it turns out it's actually not easy to mess up in a map callback. The main thing you have to avoid is side effects that modify stuff outside the callback. If you do that, the effect you'll see is those modifications only get applied once, rather than N times. And any stubs you exfiltrate from the callback simply won't work if called later.

Yeah that's what I meant, reading/writing variables captured into the callback. But that sounds like the kind of code that would be easy to sniff out in a code review, or write lints for.