Bug report: Annotation Processor NPE

[ethanhere]

Micronaut 4 annotation processor NullPointerException

We have an application based on Micronaut 3. It builds and runs fun. Recent we upgrade it with micronaut 4 and we got java.lang.NullPointerException when compiling the project. The maven build message is:
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.12.1:compile (default-compile) on project service-idm-dao-aws: Compilation failure
[ERROR] java.lang.NullPointerException: Cannot invoke "javax.lang.model.element.TypeElement.getKind()" because "type" is null
[ERROR] at io.micronaut.annotation.processing.visitor.JavaElementFactory.newSourceClassElement(JavaElementFactory.java:92)
[ERROR] at io.micronaut.annotation.processing.TypeElementVisitorProcessor.lambda$process$6(TypeElementVisitorProcessor.java:255)
[ERROR] at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
[ERROR] at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133)
[ERROR] at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1939)
[ERROR] at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
[ERROR] at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
[ERROR] at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:575)
[ERROR] at java.base/java.util.stream.AbstractPipeline.evaluateToArrayNode(AbstractPipeline.java:260)
[ERROR] at java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:616)
[ERROR] at java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:622)
[ERROR] at java.base/java.util.stream.ReferencePipeline.toList(ReferencePipeline.java:627)
[ERROR] at io.micronaut.annotation.processing.TypeElementVisitorProcessor.process(TypeElementVisitorProcessor.java:256)
[ERROR] at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(JavacProcessingEnvironment.java:1021)
[ERROR] at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(JavacProcessingEnvironment.java:937)
[ERROR] at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(JavacProcessingEnvironment.java:1265)
[ERROR] at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:1380)
[ERROR] at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1272)
[ERROR] at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:946)
[ERROR] at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:319)
[ERROR] at jdk.compiler/com.sun.tools.javac.main.Main.compile(Main.java:178)
[ERROR] at jdk.compiler/com.sun.tools.javac.Main.compile(Main.java:64)
[ERROR] at jdk.compiler/com.sun.tools.javac.Main.main(Main.java:50)

I found a workaround to get the project built by delete an @Facotory annotated class:
"
package factories;

import com.amazonaws.services.kms.AWSKMS;
import com.amazonaws.services.kms.AWSKMSClientBuilder;

import io.micronaut.context.annotation.Factory;

import jakarta.inject.Singleton;

@factory
public class AmazonKmsFactory {

@Singleton
public AWSKMS kms() {
    return AWSKMSClientBuilder.standard().build();
}

}

"

After analyzing https://github.com/micronaut-projects/micronaut-core/blob/e3f5fdb2726af5fdcab6906ad0db5165cbbb2a24/inject-java/src/main/java/io/micronaut/annotation/processing/TypeElementVisitorProcessor.java#L255 around line 255, I believe there is a bug here:
The stack trace I quoted says at io.micronaut.annotation.processing.TypeElementVisitorProcessor.lambda$process$6(TypeElementVisitorProcessor.java:255), it calls JavaElementFactory.newSourceClassElement and within newSourceClassElement method, NullPointerException was thrown.
In https://github.com/micronaut-projects/micronaut-core/blob/e3f5fdb2726af5fdcab6906ad0db5165cbbb2a24/inject-java/src/main/java/io/micronaut/annotation/processing/visitor/JavaElementFactory.java#L92 line 92, NPE was thrown because parameter type was null.
parameter type was passed from TypeElementVisitorProcessor.java:255 as typeElement
if (!elements.isEmpty()) {

            JavaElementFactory elementFactory = javaVisitorContext.getElementFactory();
            JavaElementAnnotationMetadataFactory elementAnnotationMetadataFactory = javaVisitorContext.getElementAnnotationMetadataFactory();

            // The visitor X with a higher priority should process elements of A before
            // the visitor Y which is processing elements of B but also using elements A

            // Micronaut Data use-case: EntityMapper with a higher priority needs to process entities first
            // before RepositoryMapper is going to process repositories and read entities

            List<JavaClassElement> javaClassElements = elements.stream()
                .map(typeElement -> elementFactory.newSourceClassElement(typeElement, elementAnnotationMetadataFactory))
                .toList();
        }

typeElement is an element in collection named elements. At line 243, it checks elements is not empty, but it doesn't check each element inside not null.
In fact a null element should not have been added to this collection.

Can someone take a look and fix it?

[sdelamo]

why did you report it in Micronaut Security? Do you have a sample app to reproduce it?

[ethanhere]

I didn't realize this bug reported to Micronaut-security. I think it should belong to annotation processor (if exists) or core.

[ethanhere]

I submitted a issue report : micronaut-projects/micronaut-core#10528
Please close this topic.