Android Gradle annotationProcessor not available in parent module

I'm having the following setup:

ProjectA build.gralde:

dependencies {
    compile (project(':ProjectB'))
}

ProjectB build.gradle:

dependencies {
    annotationProcessor 'com.ryanharter.auto.value:auto-value-parcel:0.2.5'
    compile "com.google.auto.value:auto-value:1.3"
    annotationProcessor "com.google.auto.value:auto-value:1.3"
}

And SomeClass in ProjectA that is implementing Parcelable

@AutoValue
public abstract class SomeClass implements Parcelable {
...
}

AutoValue won't generate any Parcelable related methods in AutoValue_SomeClass.

However, if I include auto-value-parcel annotationProcessor directly to ProjectA, the problem is resolved.

ProjectA build.gralde:

dependencies {
    compile (project(':projectB'))
    annotationProcessor 'com.ryanharter.auto.value:auto-value-parcel:0.2.5'
}

Can anyone explain how auto-value-parcel annotationProcessor is being excluded from ProjectA?

Solution

annotationProcessor dependencies are not exported to other projects. Also these are not exported with libraries.

AutoValue itself works, because you defined it with a compile dependency. This is something you should not do either. So an better dependency setup would look like...

ProjectB

dependencies {
    provided "com.jakewharton.auto.value:auto-value-annotations:$autoValueVersion"
    annotationProcessor "com.google.auto.value:auto-value:$autoValueVersion"
    annotationProcessor "com.ryanharter.auto.value:auto-value-parcel:$autoValueParcelVersion"
}

ProjectA

dependencies {
    compile project(':ProjectB')
    provided "com.jakewharton.auto.value:auto-value-annotations:$autoValueVersion"
    annotationProcessor "com.google.auto.value:auto-value:$autoValueVersion"
    annotationProcessor "com.ryanharter.auto.value:auto-value-parcel:$autoValueParcelVersion"
}

But not having annotationProcessor run on all projects would be even better.