Add Scala 3 in tests

[ennru]

Added Scala 3 even for tests and testing. Scala 3 artefacts were published even before.

[SethTisue]

the CI failure:

[error] -- Error: /home/runner/work/alpakka-kafka/alpakka-kafka/tests/src/test/java/docs/javadsl/TestkitTestcontainersTest.java:47:0 
[error] 47 |
[error]    |^^^^^^^^^
[error]    |')' expected but eof found.

it's reproducible locally with ++3.3.3; tests/Test/compile

the problem isn't fixed in 3.4.1-RC2

it's the Scala 3 compiler that's complaining, not javac. but I tried CompileOrder.JavaThenScala and CompileOrder.ScalaThenJava and that does bypass the error but then compilation doesn't ultimately succeed for other reasons, so we have to make mixed compilation work (or restructure the sources, which we'd rather not have to do)

the problematic line seems to be:

@TestInstance(TestInstance.Lifecycle.PER_CLASS)

if I comment that line out, compilation succeeds. but it's weird that other files in the same directory have the same line

if I change TestInstance.Lifecycle.PER_CLASS to null then Scala compilation succeeds (though then javac complains, as expected)

I don't see anything obviously relevant in https://github.com/scala/scala3/issues (but maybe I missed something)

not sure what to think yet. just writing down what I have so far. need to work on something else now — I'll come back to this but anyone else should feel free to take a look in the meantime

[SethTisue]

not sure what to think yet

well, I mean, it's clearly a bug in Scala 3's Java parser. it's just a matter of:

1. creating a self-contained, no-unnecessary-code-or-dependencies reproducer and filing it at https://github.com/scala/scala3/issues
2. trying to find a workaround we can use for the time being

[SethTisue]

I minimized it and filed

• In mixed compilation, Java parser can't handle JUnit annotation scala/scala3#20026

I will still try to find a way to do without the external dependency (on junit-jupiter-api)

as for workarounds, I don't see any wiggle room, can't even think of something to try

[johanandren]

Now I think it is some actual difference in behavior between Scala 2 and 3:

Logging finished for test [akka.kafka.internal.ConsumerProgressTrackingSpec: should lookup positions from the consumer when assigned] that [Failed(org.mockito.exceptions.misusing.WrongTypeOfReturnValue: 
Integer cannot be returned by position()
position() should return long