Fix: properly detect the @Generated annotation on JDK9 to avoid package splits

[zyxist]

Solution to #880.

The original issue was closed with a statement that the changes in 772374b would fix it. However, they do not. The JDK9 modular application would still have to deal with the package split, but instead of patching java.xml.ws.annotation, it would need to patch jsr250. In addition, adding this dependency pollutes the application dependencies with (mostly unnecessary) JavaEE annotations.

The solution:

• removes the import from javax.annotation.Generated, which removes the need to add any extra dependencies, and effectively removes the package split.
• properly detects the new javax.annotation.processing.Generated annotation.

I tested the solution on my experimental application, where I added Jigsaw modules: https://github.com/zyxist/dagger-example-app

Use case 1:

module com.zyxist.example.dagger.app {
    requires dagger;
    requires javax.inject;
    requires java.compiler;
}

Result: the generated classes are annotated with javax.annotation.processing.Generated.

Use case 2:

module com.zyxist.example.dagger.app {
    requires dagger;
    requires javax.inject;
    requires java.xml.ws.annotation;
}

Result: the generated classes are annotated with javax.annotation.Generated.

Use case 3:

module com.zyxist.example.dagger.app {
    requires dagger;
    requires javax.inject;
}

Result: the generated classes are not annotated.

Use case 4: using Dagger together with Guava (a library that depends on jsr305):

module com.zyxist.example.dagger.app {
    requires dagger;
    requires javax.inject;
    requires guava; // note: this is not the 'correct' module name
    requires java.compiler;
}

Result: build successful, no patching needed.

For JDK8, the annotation processor will always detect javax.annotation.Generated.

Please check if I correctly removed the jsr250 dependency from the build files. I'm new to Bazel, and I had some issues with running the full build due to the issues with Android SDK.

CLA is signed.

[zyxist]

@ronshapiro -> did you find time to take a look at the Pull Request related to javax.annotation.Generated on JDK9? I'd be really grateful for feedback, because this issue is really problematic, and it looks like other project have fallen into it, too.