Add CompletableFutures.successfulAsList

[johanburatti]

When migrating from guava ListenableFuture, we missed the Futures.successfulAsList. This implements the same functionality for CompletableFutures.

[codecov-io]

Current coverage is 100%

Merging #40 into master will not change coverage

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[mbruggmann]

👍

[mbruggmann]

Thinking about it some more, I might actually prefer to not encourage successfulAsList in Java8 and rather do something like:

Stream.of(a, b)
  .map(this::someAsyncFunction)
  .map(fallbackTo(null))
  .collect(joinList())

This makes it more obvious at the call site that you introduce null values in the result. Any strong opinions @dflemstr @spkrka?

[spkrka]

I haven't though about it a whole lot, but my gut feeling agrees with you. Alternatively we could have successfulAsList(defaultValue, futures) or successfulAsList(t -> toValue(t), futures) - then it would also be more obvious how failures are converted to values instead of always returning null

[johanburatti]

I think the points you make are very valid. When migrating from ListanebleFuture we only duplicated that behavior, which I agree is not optimal.

Personally I think I like the suggestion of @spkrka with a lambda since that is still much more convenient to type and easier to understand when reading than the stream-based one. @mbruggmann if you agree, I will change successfulAsList to require a function from throwable to value as well.

[johanburatti]

Updated after comments

[mbruggmann]

👍 for the implementation. Only nitpick left: Should this really be successfulAsList now or rather an overload of allAsList?

[johanburatti]

Regarding naming it allAsListnow, I disagree. I think it is different enough to be named something else. Also, successfulAsList is what the corresponding guava method is called.

[johanburatti]

Sorry about the delay... Updated PR with rebased change. Added javadoc for .

[mbruggmann]

I think this is good to merge now. @dflemstr @spkrka any last minute concerns?

[spkrka]

No strong opinions from me