Unable to detect multiple parameter annotations with different RetentionPolicies.

The issue is that parameter annotations with RetentionPolicy.RUNTIME doesn’t work when the parameter also has another annotation with RetentionPolicy.CLASS.

Tested with master branch - version 4.8.22-SNAPSHOT (352eb88)

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
public @interface AnnoRuntime { }

@Retention(RetentionPolicy.CLASS)
@Target(ElementType.PARAMETER)
public @interface AnnoClass { }

public void function(@AnnoRuntime @AnnoClass int arg) { }

[lukehutch]

@T101N I found the source of the problem. In the classfile format, RuntimeVisibleParameterAnnotations and RuntimeInvisibleParameterAnnotations are listed in separate method attributes, and both of them can be present with separate arrays of annotations for the method. I was overwriting the method parameter annotations for the second attribute, rather than extending the arrays of annotations already read for the first attribute in order to merge together both annotation arrays into a single array of annotations for each method parameter.

Eclipse seems to only reliably fail if commandline Maven (commandline javac) last built the project, not ecj. However I saw some nondeterminacy between different runs on the commandline. Apparently javac uses a Set for storing annotations by retention type, and uses a nondeterministic hash function, probably based on the class reference (so the order in which classes are loaded can actually change the order that attributes are written to the classfile).

Released (and should be fixed) in 4.8.22. Thank you for the comprehensive testcase code!

[lukehutch]

Interesting… No filtering is applied while an AnnotationInfoList is being constructed though, and there should be no state carried over from annotation to annotation. The parameter annotation info is read here:

https://github.com/classgraph/classgraph/blob/master/src/main/java/io/github/classgraph/Classfile.java#L1259

The AnnotationInfoList is built here:

https://github.com/classgraph/classgraph/blob/master/src/main/java/io/github/classgraph/MethodParameterInfo.java#L175

It’s all pretty straightforward…

There have been Kotlin issues in the past, see:

https://github.com/classgraph/classgraph/blob/master/src/main/java/io/github/classgraph/MethodInfo.java#L375