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Varargs methods cause ClassCastException in AnswerFunctionalInterfaces #2644

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5 tasks done
perlun opened this issue May 17, 2022 · 4 comments · Fixed by #2664
Closed
5 tasks done

Varargs methods cause ClassCastException in AnswerFunctionalInterfaces #2644

perlun opened this issue May 17, 2022 · 4 comments · Fixed by #2664

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@perlun
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perlun commented May 17, 2022

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
  • Read the contributing guide
@perlun perlun mentioned this issue May 17, 2022
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@big-andy-coates
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I've had a bit of a dig and it looks like a bug to me. returnsArgAt has similar issues. I'm happy to have a look into this.

big-andy-coates added a commit to big-andy-coates/mockito that referenced this issue Jun 2, 2022
@big-andy-coates
Improve Varargs handling in AdditionalAnswers
057c795 
Fixes: mockito#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,

```java
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", ""]`.
@big-andy-coates big-andy-coates mentioned this issue Jun 2, 2022
Merged
8 tasks
big-andy-coates added a commit to big-andy-coates/mockito that referenced this issue Jun 6, 2022
@big-andy-coates
Improve Varargs handling in AdditionalAnswers
7cbc653 
Fixes: mockito#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,

```java
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", ""]`.
big-andy-coates added a commit to big-andy-coates/mockito that referenced this issue Jun 6, 2022
@big-andy-coates
Improve Varargs handling in AdditionalAnswers
459efad 
Fixes: mockito#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,

```java
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", ""]`.
TimvdLippe pushed a commit that referenced this issue Jun 11, 2022
@big-andy-coates
Improve Varargs handling in AdditionalAnswers (#2664)
ce4e64d 
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,

```java
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", ""]`.

Fixes #2644
@perlun
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perlun commented Jul 4, 2022

Thanks for the fix @big-andy-coates & @TimvdLippe, appreciated!

@gastaldi gastaldi mentioned this issue Aug 15, 2022
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@perlun
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perlun commented Aug 30, 2022 •
edited
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(Verified in our project that the fix indeed fixes the original problem. Thanks! 🙏)

@perlun
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perlun commented Nov 18, 2022

Semi-related issue discovered today: #2664 (comment)

@big-andy-coates big-andy-coates mentioned this issue Nov 22, 2022
Closed
@DaveTryon DaveTryon mentioned this issue Jan 11, 2023
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Improve Varargs handling in AdditionalAnswers big-andy-coates/mockito
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@perlun @big-andy-coates