Opentelemetry-java: SpanWrapper (SpanData) does not snapshot the value of hasEnded.

[Oberon00]

Describe the bug
io.opentelemetry.sdk.trace.SpanWrapper does not store the value of hasEnded, updates to the originial Span will be inadvertedly reflected in the SpanData.

Steps to reproduce

SpanData sd = someSpan.toSpanData();
assertThat(sd.hasEnded()).isFalse();
someSpan.end();
assertThat(sd.hasEnded()).isFalse(); // Fails!

What did you expect to see?
No assertion failure -- SpanData should be immutable.

What did you see instead?
Assertion failure -- SpanData was modified.

What version and what artifacts are you using?
Master @ 8005c7eddd456b91023c661e8e9a9e37f641c9bb

Additional context
This can cause trouble when working with un-ended spans and multiple threads.

[bogdandrutu]

Haha 👍 I would like to close this as "working as intended" :)

SpanData is an immutable snapshot of the current Span, all data recorded after that will not reflect in SpanData.

This can cause trouble when working with un-ended spans and multiple threads.

Indeed the main reason to not support this.

[iNikem]

@bogdandrutu I think the original report was exactly that SpanData is NOT immutable right now.

[Oberon00]

Yes, maybe "preserve" was not the best word choice. It inadvertedly reflects changing hasEnded in the Span.

[Oberon00]

After reading the code, it seems that name and endTimestamp are also read from the span instead of being part of the snapshot. Also, I couldn't find any unit tests that would guard against changes to any span property being reflected in the SpanData at all (not even for properties where it should work).

I will prepare a PR.

[carlosalberto]

SpanData is an immutable snapshot of the current Span

Oh my, I totally oversaw the fact this is against SpanData directly, not Span returning an outdated SpanData ;) So yes, this is not an actual bug.

[Oberon00]

I think it is a bug. The @Immutable annotation on SpanData/SpanWrapper is violated. EDIT: It's also a regression, because previous versions did snapshot these values.