Improve Varargs handling in AdditionalAnswers

[big-andy-coates]

Fixes: #2644

Fixes issues around vararg handling for the following methods in AdditionalAnswers:

• returnsFirstArg
• returnsSecondArg
• returnsLastArg
• returnsArgAt
• answer
• answerVoid

These methods were not correctly handling varargs. For example,

doAnswer(answerVoid(
      (VoidAnswer2<String, Object[]>) logger::info
   )).when(mock)
      .info(any(), (Object[]) any());

mock.info("Some message with {} {} {}", "three", "parameters", "");

Would previously have resulted in a ClassCastException being thrown from the mock.info call. This was because the answerVoid method was not taking into account that the second parameter was a varargs parameter and was attempting to pass the second actual argument "three", rather than the second raw argument ["three", "parameters", ""].

The fix is to add checks for varargs methods and, when encountered, check to see if the required parameter type is the raw varargs type or the its component type.

Checklist

• Read the contributing guide
• PR should be motivated, i.e. what does it fix, why, and if relevant how
• If possible / relevant include an example in the description, that could help all readers
  including project members to get a better picture of the change
• Avoid other runtime dependencies
• Meaningful commit history ; intention is important please rebase your commit history so that each
  commit is meaningful and help the people that will explore a change in 2 years
• The pull request follows coding style
• Mention Fixes #<issue number> in the description if relevant
• At least one commit should mention Fixes #<issue number> if relevant

[big-andy-coates]

@TimvdLippe any chance of a quick review to check I'm going in the right direction with this before I flesh out all the testing and clean up the code?

[codecov-commenter]

Codecov Report

Merging #2664 (7ed9b26) into main (1fbef57) will increase coverage by 0.03%.
The diff coverage is 90.16%.

@@             Coverage Diff              @@
##               main    #2664      +/-   ##
============================================
+ Coverage     86.22%   86.26%   +0.03%     
- Complexity     2763     2776      +13     
============================================
  Files           314      315       +1     
  Lines          8290     8334      +44     
  Branches       1031     1037       +6     
============================================
+ Hits           7148     7189      +41     
- Misses          873      874       +1     
- Partials        269      271       +2     

Impacted Files	Coverage Δ
...l/stubbing/answers/AnswerFunctionalInterfaces.java	94.79% <88.09%> (-5.21%)	⬇️
...o/internal/stubbing/answers/ReturnsArgumentAt.java	98.21% <94.44%> (-1.79%)	⬇️
...l/stubbing/defaultanswers/ForwardsInvocations.java	100.00% <100.00%> (ø)
...rg/mockito/internal/creation/MockSettingsImpl.java	88.11% <0.00%> (ø)
src/main/java/org/mockito/Mock.java	100.00% <0.00%> (ø)
...nternal/configuration/MockAnnotationProcessor.java	97.14% <0.00%> (+0.08%)	⬆️
.../mockito/internal/stubbing/StrictnessSelector.java	100.00% <0.00%> (+60.00%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1fbef57...7ed9b26. Read the comment docs.

[big-andy-coates]

@TimvdLippe any chance of a review please?

[TimvdLippe]

I have a very busy week this week. I will likely get to this early next week.

[TimvdLippe]

Solid work and great test coverage! Only two small nits, but other than this it is ready to go 🎉

[TimvdLippe]

Thanks!

[big-andy-coates]

No worries. Good to give something back. I've used Mockito for YEARS!

[perlun]

@big-andy-coates I found a similar semi-related issue I think... With 4.7.0, this now works correctly:

        doAnswer(answerVoid((VoidAnswer2<String, Object[]>)
                logger::info
        )).when(mock)
                .info(any(), (Object[]) any());

However, if I try to use this form which is slightly more ergonomic:

        doAnswer( answerVoid( (VoidAnswer2<String, Object[]>)
                logger::info
        ) ).when( mock )
                .info( any(), any( Object[].class ) );

...the mocking will fail to intercept these method calls. 🤔 No error when creating the mock, but it just won't detect the method calls as expected.

I presume this has again something to do with the varargs parsing. javac resolves those two calls to the correct/same logger.info() overload, so so far so good.

Do you want me to create a separate issue/repro repo for this? I'm not even sure if it's something that can be (easily) fixed, I just happened to see it now while trying to "clean up our code"... 😅