@Inject fields in abstract classes not properly injected

[rsenden]

Expected Behavior

In our Micronaut/Picocli based command line application, we have multiple abstract classes containing fields annotated with @Inject. These abstract classes are used as base classes for concrete Picocli @Command implementations. We'd expect Micronaut to properly inject these fields with the corresponding @Singleton instances.

Actual Behaviour

• If there are any custom annotations (defined in our own com.fortify.* package) present in either the abstract base class or the concrete command implementation, the fields annotated with @Inject get injected properly.
• If there are only standard annotations (from java.lang, picocli, Jackson, ...) present in the class hierarchy, the fields annotated with @Inject do not get injected and remain null.

Steps To Reproduce

1. Clone sample project https://github.com/rsenden/micronaut-inject-issue
2. Run ./gradlew clean shadowJar
3. Run java -jar build/libs/mncli.jar annotated-superclass; outputs Singleton called
4. Run java -jar build/libs/mncli.jar annotated-subclass; outputs Singleton called
5. Run java -jar build/libs/mncli.jar field-annotation; outputs Singleton called
6. Run java -jar build/libs/mncli.jar no-annotation; fails with NPE because singleton was not injected
7. Run java -jar build/libs/mncli.jar standard-annotation; fails with NPE because singleton was not injected

Environment Information

• Operating system: Ubuntu 22.04.1 LTS running under Windows Subsystem for Linux 2 (WSL2)
• Java version: Openjdk version "11.0.16" 2022-07-19

Example Application

https://github.com/rsenden/micronaut-inject-issue

Version

3.4.2

[rsenden]

This seems to be somewhat related to the following block in build.gradle:

micronaut {
    testRuntime("junit5")
    processing {
        incremental(true)
        annotations("org.sample.micronaut.*")
    }
}

The annotations option in combination with our custom annotations seems to make Micronaut properly process class hierarchies that have any of our custom annotations. Removing the annotations option makes the other commands (with our custom annotations) fail as well.

However, I'd expect Micronaut to automatically pick up any jakarta.inject annotations independent of whether there are any custom annotations defined in the class hierarchy. Also, removing the annotations option (just in case we are overriding some defaults like jakarta.inject.*), or explicitly specifying annotations("jakarta.inject.*") doesn't fix the issue.

[qolsoftware]

I ran into a similar problem. I discovered if the abstract class has an @Inject field, that doesn't make the subclass a Micronaut bean. You need to either add an @Inject field to the subclass or make it @Singleton or @Prototype.