DelegatingCompletableFuture.cancel() returns false for already cancelled future [SPR-17337]

[spring-projects-issues]

Ivan Sopov opened SPR-17337 and commented

Sorry - JIRA failed me many times in filling this issue (one time I retyped it from the beginning), so I filled it on Gist:
https://gist.github.com/isopov/b2dca9d7152f577741c8451d91e97e37
This is somewhat related to #21870

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Affects: 5.1 GA

Issue Links:

• MonoToListenableFutureAdapter.cancel problems [SPR-17336] #21870 MonoToListenableFutureAdapter.cancel problems

[bclozel]

Thanks for raising this issue Ivan, and sorry it took us so long to reply.
I agree that this subtle difference is quite tricky. The JavaDoc of Future does say that Implementations may provide stronger guarantees, but here it's really a behavior change. Our delegation implementation... delegates and the cancel() behavior isn't well defined.

Anyway ListenableFuture has been deprecated as of 6.0 in the meantime, so I don't think we should change the behavior now right before retiring it completely.