Miss Dada  🏳️‍⚧️

what's the rust thing for turning a Vec<Result> (or an Iterator<Item = Result>) into a Result<Vec>

getting Vec<Result> from the Iterator is just collect(), but I'm not sure about Result<Vec>

so thanks to @bodil it turns out this is also just a call to collect(), you just say you want a Result<Vec<_>, _>, b/c Result<V, E> implements FromIterator<Result<A, E>> where V: FromIterator<A>

this is honestly still kind of magical to me even after writing thousands of words about it https://blog.jcoglan.com/2019/04/22/generic-returns-in-rust/ …

so, it occurs to me that this is a gap in the rust docs -- trait implementations don't typically get docs shown, e.g. https://doc.rust-lang.org/std/result/enum.Result.html#impl-FromIterator%3CResult%3CA%2C%20E%3E%3E …

the implementation of <Result<V, E> as FromIterator<Result<A, E>>::from_iter is far from obvious and has behaviour that's only apparent from reading the source

it has behaviour somewhat like Promise.all in JS: if any items in the iterator are Err, you get an Err, otherwise you get an Ok with the desired collection type

this it not at all unreasonable behaviour, it's just not obvious, and I might expect different behaviour for other monads e.g. I think it would be reasonable for FromIterator<Option<A>> for Option<V> to return a V containing only the Some items