Consuming MergeMany via for await loses values

Using Swift
, ,
1

In an iOS app which generally prefers async/await over Combine, we have this situation.
6 CurrentValueSubject<String,Never> instances which are being consumed like so:

for await value in Publishers.MergeMany(subjects)
                .values {
                  //... do something with `value`
            }

When I throw many values at the subjects in a unit test (concurrently), values are being dropped (the for await only sees a small portion of them). If I change to using sink, everything works fine. I can do this, but just wondering what the explanation is -- lack of buffering/backpressure in the AsyncPublisher returned by .values?

Thanks for any insight.

2

This is the buffering strategy when using Publisher.values / AsyncPublisher.

I have not used this but I guess its possible to use Publishers.Buffer to buffer all values:

Publishers.MergeMany(subjects)
    .buffer(size: .max, prefetch: .byRequest, whenFull: .dropOldest)
    .values

While its a little more work, I prefer to create my own sequence that creates an inner AsyncStream for each iterator, sinking values from publisher to the stream and cancelling when the iterator is destroyed.