Does not work with android plugin

[ghost]

This plugin does not work with the android plugin for gradle, since it applies the java plugin.

[ejona86]

Try adding remove java within the builtins section.

[AstralStorm]

Same issue, that remove java is not the problem nor fixes it.

The problem is here: https://github.com/google/protobuf-gradle-plugin/blob/master/src/main/groovy/com/google/protobuf/gradle/ProtobufPlugin.groovy#L70

This protobuf plugin just does not support android plugin.

[zhangkun83]

The problem with the android plugin is more than just that it cannot be applied when the java plugin has already been applied. The android project is structured differently from a java project.

Here I managed to get the nano protos compiled in an android project. It doesn't look very nice. The Android plugin uses a sourceSet inside the android block, not on the top-level. Ideally I should insert the proto convention to the android sourceSet, but I haven't figured out how.

[zhangkun83]

One more android plugin quirk gets in my way.

I tried to have the protobuf plugin to call android.sourceSets.<sourceSet>.java.srcDir to add generated sources, just like what we have been doing with java plugin. This can only be done in the project.afterEvaluate hook because only at that point have the proto source sets been evaluated. However, it just doesn't work. It seems the android plugin only reads android.sourceSets BEFORE this point. After that, any changes to android.sourceSets will have no effect.

An experiment to illustrate the problem. In ProtobufPlugin.apply(), which is run when the user does apply plugin: 'com.google.protobuf', if I add the line below, files under build/generated-sources/main will be compiled.

project.android.sourceSets.main.java.srcDir("build/generated-sources/main")

If I do this instead, they won't:

project.afterEvaluate {
  project.android.sourceSets.main.java.srcDir("build/generated-sources/main")
}

This makes it impossible to continue specifying proto files and options inside sourceSets and make it work with android plugin. I am thinking of using our own conventions/functions to do this, which is more flexible, e.g., we can then change android.sourceSets at evaluation time, then the changes can be picked up by android plugin when it compiles the sources.

[zhangkun83]

Anyway, although putting everything in sourceSets along with the java sources looks very nice from user's aspect, I have been uncomfortable with the fact that the implementation uses Gradle internal API and undocumented internal features. It is very fragile.

[AstralStorm]

What about com.android.library?

[zhangkun83]

So, this was unintentionally closed. I have checked in a comprehensive solution for Android, which should work for both library and application. It will be released as 0.5.0. Soon I will create a release branch for it, and update README in there.

[zhangkun83]

I have created the v0.5.x branch. Please follow its README and try it out. You may want to refer to testProjectAndroid as a working example for Android.

@madongfly

[mnvl]

I had manually add dependency to protobuf-nano:

dependencies {
    compile 'com.google.protobuf.nano:protobuf-javanano:3.0.0-alpha-3.1'
}

[mnvl]

It would be nice to be able to use javanano generated code with java projects and java generated code with android projects though. If I add

        all()*.builtins {
            java {
            }
        }

then it ends up generating both java and javanano classes and compilation fails because it finds duplicate classes.

[zhangkun83]

@manvelavetisian The java builtin is added automatically in Java projects, and so is javanano in Android projects. If you want java builtin instead in an Android project, you need to remove javanano explicitly:

all()*.builtins {
  remove javanano
  java {
  }
}

[zhangkun83]

0.5.0 has been released. Please refer to the instructions from the master README.