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Varargs methods cause ClassCastException in AnswerFunctionalInterfaces #2644
Description
Hi,
The other day, I discovered that this code does not work:
doAnswer(answerVoid((VoidAnswer2<String, Object[]>)
logger::info
)).when(mock)
.info(any(), (Object[]) any());
// This call will throw an exception
mock.info("Some message with {} {} {}", "three", "parameters", "");The exception details looks as follows:
class java.lang.String cannot be cast to class [Ljava.lang.Object; (java.lang.String and [Ljava.lang.Object; are in module java.base of loader 'bootstrap')
java.lang.ClassCastException: class java.lang.String cannot be cast to class [Ljava.lang.Object; (java.lang.String and [Ljava.lang.Object; are in module java.base of loader 'bootstrap')
at org.mockito.internal.stubbing.answers.AnswerFunctionalInterfaces$4.answer(AnswerFunctionalInterfaces.java:97)
at org.mockito.internal.stubbing.answers.AnswerFunctionalInterfaces$4.answer(AnswerFunctionalInterfaces.java:93)
at org.mockito.internal.stubbing.StubbedInvocationMatcher.answer(StubbedInvocationMatcher.java:42)
at org.mockito.internal.handler.MockHandlerImpl.handle(MockHandlerImpl.java:103)
at org.mockito.internal.handler.NullResultGuardian.handle(NullResultGuardian.java:29)
at org.mockito.internal.handler.InvocationNotifierHandler.handle(InvocationNotifierHandler.java:34)
at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:82)
at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor.doIntercept(MockMethodInterceptor.java:56)
at org.mockito.internal.creation.bytebuddy.MockMethodInterceptor$DispatcherDefaultingToRealMethod.interceptAbstract(MockMethodInterceptor.java:161)
at org.slf4j.Logger$MockitoMock$f4Org7xs.info(Unknown Source)
at LoggerMockingTest.logger_info_can_be_called_without_exceptions(LoggerMockingTest.java:34)
[...]
The following works, but feels much less elegant:
doAnswer( invocation -> {
String format = invocation.getArgument( 0 );
Object[] allArguments = invocation.getArguments();
Object[] arguments = Arrays.copyOfRange( allArguments, 1, allArguments.length );
logger.info( format, arguments );
return null;
} ).when( mock )
.info( anyString(), (Object[])any() );Is this to be considered a bug or a feature? 🙂 I get the feeling that varargs (Object[] under the hood) parameters do not really work when used with the answerVoid()-based approach as described above.
Full MCVE
https://github.com/perlun/mockito-slf4-logging-example
Issue checks
- The mockito message in the stacktrace have useful information, but it didn't help
- The problematic code (if that's possible) is copied here;
Note that some configuration are impossible to mock via Mockito - Provide versions (mockito / jdk / os / any other relevant information): Reproduced with latest Mockito, 4.5.1
- Provide a Short, Self Contained, Correct (Compilable), Example of the issue
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Activity
big-andy-coates commentedon Jun 1, 2022
I've had a bit of a dig and it looks like a bug to me.
returnsArgAthas similar issues. I'm happy to have a look into this.Improve Varargs handling in AdditionalAnswers
Improve Varargs handling in AdditionalAnswers
Improve Varargs handling in AdditionalAnswers
Improve Varargs handling in AdditionalAnswers (#2664)
perlun commentedon Jul 4, 2022
Thanks for the fix @big-andy-coates & @TimvdLippe, appreciated!
perlun commentedon Aug 30, 2022
(Verified in our project that the fix indeed fixes the original problem. Thanks! 🙏)
perlun commentedon Nov 18, 2022
Semi-related issue discovered today: #2664 (comment)