Java null pointer exception in using invokePrivate

[Eric Fowler]

I have a class:

class MyClass

{

def foo(s:String) : Unit = {/*nothing important*/}

}

And a scalatest that tests for null input data. This test worked back when foo was public: 

"My test" should "not choke on null data" in {

val mc = new MyClass

mc.foo(null) .... mumble .... whatever

}

All good. 

Now I make foo private, and rejigger the test to use privateInvoke:

"My test" should "not choke on null data" in {

import org.scalatest.PrivateMethodTester._

val mc = new MyClass

val foo = PrivateMethod[Unit]('foo)

mc invokePrivate foo(null) .... mumble .... whatever

}

For this, I get something that looks like this. 

The salient point is (1) it is expecting an InvalidArgumentException (why?) and (2)  it got a NullPointerException (why?)

Anyone know what is going on here?

java.lang.NullPointerException was thrown.

java.lang.NullPointerException

at org.scalatest.PrivateMethodTester$Invoker.org$scalatest$PrivateMethodTester$Invoker$$argMatchesParamType$1(PrivateMethodTester.scala:196)

at org.scalatest.PrivateMethodTester$Invoker$$anonfun$2.apply(PrivateMethodTester.scala:203)

at org.scalatest.PrivateMethodTester$Invoker$$anonfun$2.apply(PrivateMethodTester.scala:203)

at scala.collection.TraversableLike$WithFilter$$anonfun$withFilter$1.apply(TraversableLike.scala:789)

at scala.collection.TraversableLike$WithFilter$$anonfun$withFilter$1.apply(TraversableLike.scala:789)

at scala.collection.TraversableLike$WithFilter$$anonfun$map$2.apply(TraversableLike.scala:728)

at scala.collection.immutable.List.foreach(List.scala:381)

at scala.collection.TraversableLike$WithFilter.map(TraversableLike.scala:727)

at org.scalatest.PrivateMethodTester$Invoker.argsHaveValidTypes$1(PrivateMethodTester.scala:203)

at org.scalatest.PrivateMethodTester$Invoker.org$scalatest$PrivateMethodTester$Invoker$$isMethodToInvoke$1(PrivateMethodTester.scala:237)

at org.scalatest.PrivateMethodTester$Invoker$$anonfun$4.apply(PrivateMethodTester.scala:243)

at org.scalatest.PrivateMethodTester$Invoker$$anonfun$4.apply(PrivateMethodTester.scala:243)

at scala.collection.TraversableLike$WithFilter$$anonfun$map$2.apply(TraversableLike.scala:728)

at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)

at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:186)

at scala.collection.TraversableLike$WithFilter.map(TraversableLike.scala:727)

at org.scalatest.PrivateMethodTester$Invoker.invokePrivate(PrivateMethodTester.scala:243)

at FeasibilityTest$$anonfun$11.apply$mcV$sp(FeasibilityTest.scala:115)

at FeasibilityTest$$anonfun$11.apply(FeasibilityTest.scala:106)

at FeasibilityTest$$anonfun$11.apply(FeasibilityTest.scala:106)

at org.scalatest.Transformer$$anonfun$apply$1.apply$mcV$sp(Transformer.scala:22)

at org.scalatest.OutcomeOf$class.outcomeOf(OutcomeOf.scala:85)

at org.scalatest.OutcomeOf$.outcomeOf(OutcomeOf.scala:104)

at org.scalatest.Transformer.apply(Transformer.scala:22)

at org.scalatest.Transformer.apply(Transformer.scala:20)

at org.scalatest.FlatSpecLike$$anon$1.apply(FlatSpecLike.scala:1647)

at org.scalatest.Suite$class.withFixture(Suite.scala:1122)

at org.scalatest.FlatSpec.withFixture(FlatSpec.scala:1683)

at org.scalatest.FlatSpecLike$class.invokeWithFixture$1(FlatSpecLike.scala:1644)

at org.scalatest.FlatSpecLike$$anonfun$runTest$1.apply(FlatSpecLike.scala:1656)

at org.scalatest.FlatSpecLike$$anonfun$runTest$1.apply(FlatSpecLike.scala:1656)

at org.scalatest.SuperEngine.runTestImpl(Engine.scala:306)

at org.scalatest.FlatSpecLike$class.runTest(FlatSpecLike.scala:1656)

at org.scalatest.FlatSpec.runTest(FlatSpec.scala:1683)

at org.scalatest.FlatSpecLike$$anonfun$runTests$1.apply(FlatSpecLike.scala:1714)

at org.scalatest.FlatSpecLike$$anonfun$runTests$1.apply(FlatSpecLike.scala:1714)

at org.scalatest.SuperEngine$$anonfun$traverseSubNodes$1$1.apply(Engine.scala:413)

at org.scalatest.SuperEngine$$anonfun$traverseSubNodes$1$1.apply(Engine.scala:401)

at scala.collection.immutable.List.foreach(List.scala:381)

at org.scalatest.SuperEngine.traverseSubNodes$1(Engine.scala:401)

at org.scalatest.SuperEngine.org$scalatest$SuperEngine$$runTestsInBranch(Engine.scala:390)

at org.scalatest.SuperEngine$$anonfun$traverseSubNodes$1$1.apply(Engine.scala:427)

at org.scalatest.SuperEngine$$anonfun$traverseSubNodes$1$1.apply(Engine.scala:401)

at scala.collection.immutable.List.foreach(List.scala:381)

at org.scalatest.SuperEngine.traverseSubNodes$1(Engine.scala:401)

at org.scalatest.SuperEngine.org$scalatest$SuperEngine$$runTestsInBranch(Engine.scala:396)

at org.scalatest.SuperEngine.runTestsImpl(Engine.scala:483)

at org.scalatest.FlatSpecLike$class.runTests(FlatSpecLike.scala:1714)

at org.scalatest.FlatSpec.runTests(FlatSpec.scala:1683)

at org.scalatest.Suite$class.run(Suite.scala:1424)

at org.scalatest.FlatSpec.org$scalatest$FlatSpecLike$$super$run(FlatSpec.scala:1683)

at org.scalatest.FlatSpecLike$$anonfun$run$1.apply(FlatSpecLike.scala:1760)

at org.scalatest.FlatSpecLike$$anonfun$run$1.apply(FlatSpecLike.scala:1760)

at org.scalatest.SuperEngine.runImpl(Engine.scala:545)

at org.scalatest.FlatSpecLike$class.run(FlatSpecLike.scala:1760)

at org.scalatest.FlatSpec.run(FlatSpec.scala:1683)

at org.scalatest.tools.SuiteRunner.run(SuiteRunner.scala:55)

at org.scalatest.tools.Runner$$anonfun$doRunRunRunDaDoRunRun$3.apply(Runner.scala:2563)

at org.scalatest.tools.Runner$$anonfun$doRunRunRunDaDoRunRun$3.apply(Runner.scala:2557)

at scala.collection.immutable.List.foreach(List.scala:381)

at org.scalatest.tools.Runner$.doRunRunRunDaDoRunRun(Runner.scala:2557)

at org.scalatest.tools.Runner$$anonfun$runOptionallyWithPassFailReporter$2.apply(Runner.scala:1044)

at org.scalatest.tools.Runner$$anonfun$runOptionallyWithPassFailReporter$2.apply(Runner.scala:1043)

at org.scalatest.tools.Runner$.withClassLoaderAndDispatchReporter(Runner.scala:2722)

at org.scalatest.tools.Runner$.runOptionallyWithPassFailReporter(Runner.scala:1043)

at org.scalatest.tools.Runner$.run(Runner.scala:883)

at org.scalatest.tools.Runner.run(Runner.scala)

at org.jetbrains.plugins.scala.testingSupport.scalaTest.ScalaTestRunner.runScalaTest2(ScalaTestRunner.java:138)

at org.jetbrains.plugins.scala.testingSupport.scalaTest.ScalaTestRunner.main(ScalaTestRunner.java:28)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:483)

at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)

Expected exception java.lang.IllegalArgumentException to be thrown, but java.lang.NullPointerException was thrown.

[Eric Fowler]

Doing a little more investigating, it seems to be having trouble here:

case _ => paramType.isAssignableFrom(anyRefArg.getClass)

The type matching system is having trouble with that null parameter. 

I was lying earlier, I'm not passing a string. Actually I am passing one of these: 

class MyClass

Which should look familiar to all of you. 

How can I tell it what type to expect? 

I tried calling it like this: 

mc invokePrivate foo(null:String)

Which, amazingly, compiled, but also failed. 

[Bill Venners]

Hi Eric,

What is the method supposed to do when null is passed?

Bill

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Bill Venners
Artima, Inc.
http://www.artima.com

[Eric Fowler]

It handles it ... basically a null result. But no exceptions. 

The original function takes three vertices, and splices the third one between the first two. If the second is null, the new vertex is appended; if the first is null, it is prepended; if both are null, the third is added to a list as it's sole member. 

Eric

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[Bill Venners]

Hi Erik,

Yes, it looks like I never imagined someone passing in null. I think
we will have to enhance PrivateMethodTester to allow null to be
passed.

Bill