Include classname of null-returning map function in NPE msg

[ismailalammar]

linked issue #2982

this PR include :

• log class name in (FluxMap - FluxMapSignal - FluxMapFuseable) if mapper returns null.

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[simonbasle]

thanks @ismailalammar !
as I stated in the issue, this should have been opened against the 3.4.x branch.
you will need to git rebase -i 3.4.x and drop the commits that don't belong to the PR, then I can edit the PR target (or you can do it if you're familiar with the procedure).

Also, can you try to add tests for these in FluxMapTest and FluxMapSignalTest?
In FluxMapTest there is a mapperReturnsNull test but it is using an old style (no StepVerifier), doesn't assert the message of the NullPointerException and only covers a fused case.

[JamesChenX]

For better performance, we can concat the strings only after checking the return value is null. e.g.:

Object value = mapper.apply(t);
if (value == null) {
    throw new NullPointerException("The mapper [" + mapper.getClass().getName() + "] returned a null value.");
}

[ismailalammar]

sure will change it , thanks @JamesChenX

[ismailalammar]

thanks @ismailalammar ! as I stated in the issue, this should have been opened against the 3.4.x branch. you will need to git rebase -i 3.4.x and drop the commits that don't belong to the PR, then I can edit the PR target (or you can do it if you're familiar with the procedure).

Also, can you try to add tests for these in FluxMapTest and FluxMapSignalTest? In FluxMapTest there is a mapperReturnsNull test but it is using an old style (no StepVerifier), doesn't assert the message of the NullPointerException and only covers a fused case.

sure , will do

[simonbasle]

@ismailalammar any progress on this? do you need help with writing the tests?

[He-Pin]

Can it rightly retrieve the lambda's line numbers too?

[simonbasle]

Can it rightly retrieve the lambda's line numbers too?

I would rather rely on Java 14+ "better NPE" feature.

Here there isn't really a lambda line to communicate, because the lambda itself doesn't throw, it merely returns null.

[ismailalammar]

i am so sorry i missed this ticket , got blocked with amount of work in the past few weeks.

i don't think i will be able to complete the test cases in the near future . apologize for that

[reactorbot]

@simonbasle this PR seems to have been merged on a maintenance branch, please ensure the change is merge-forwarded to intermediate maintenance branches and up to main 🙇