Support packaging and extracting protos in Android aar (take 2) (#443)

Fixes the issue of ExtractIncludeProto tasks failing to match dependencies, which was caused by the previous commit trying to extract included protos for each Android source set instead for each variant.

Android projects should extract included protos from each variant's compileClasspath as variants are compilation units for Android projects. So we will not create compileProtoPath configurations for Android source sets.

This change includes an integration test for covering packaging/extracting protos in AAR.

src/main/groovy/com/google/protobuf/gradle/ProtobufPlugin.groovy

@@ -38,6 +38,7 @@ import org.gradle.api.Plugin
 import org.gradle.api.Project
 import org.gradle.api.Task
 import org.gradle.api.artifacts.Configuration
+import org.gradle.api.attributes.Attribute
 import org.gradle.api.attributes.LibraryElements
 import org.gradle.api.file.FileCollection
 import org.gradle.api.file.SourceDirectorySet
@@ -130,8 +131,15 @@ class ProtobufPlugin implements Plugin<Project> {
         project.afterEvaluate {
           // All custom source sets, configurations created by other plugins,
           // and Android variants are only available at this point.
-          getSourceSets().each { sourceSet ->
-            createCompileProtoPathConfiguration(sourceSet.name)
+
+          // Java projects will extract included protos from a 'compileProtoPath'
+          // configuration of each source set, while Android projects will
+          // extract included protos from {@code variant.compileConfiguration}
+          // of each variant.
+          if (!Utils.isAndroidProject(project)) {
+            getSourceSets().each { sourceSet ->
+                createCompileProtoPathConfiguration(sourceSet.name)
+            }
           }
           addProtoTasks()
           project.protobuf.runTaskConfigClosures()
@@ -173,6 +181,7 @@ class ProtobufPlugin implements Plugin<Project> {
      * The extract-include-protos task of each source set will extract protobuf files from
      * dependencies in this configuration.
      *
+     * <p> For Java projects only.
      * <p> This works around 'java-library' plugin not exposing resources to consumers for compilation.
      */
     private void createCompileProtoPathConfiguration(String sourceSetName) {
@@ -267,6 +276,7 @@ class ProtobufPlugin implements Plugin<Project> {
      * Creates Protobuf tasks for a variant in an Android project.
      */
     private void addTasksForVariant(final Object variant, boolean isTestVariant) {
+      // GenerateProto task, one per variant (compilation unit).
       Task generateProtoTask = addGenerateProtoTask(variant.name, variant.sourceSets)
       generateProtoTask.setVariant(variant, isTestVariant)
       generateProtoTask.flavors = ImmutableList.copyOf(variant.productFlavors.collect { it.name } )
@@ -275,19 +285,37 @@ class ProtobufPlugin implements Plugin<Project> {
       }
       generateProtoTask.doneInitializing()
 
+      // ExtractIncludeProto task, one per variant (compilation unit).
+      // Proto definitions from an AAR dependencies are in its JAR resources.
+      Attribute artifactType = Attribute.of("artifactType", String)
+      FileCollection classPathConfig = variant.compileConfiguration.incoming.artifactView {
+        attributes {
+            it.attribute(artifactType, "jar")
+        }
+      }.files
+      FileCollection testClassPathConfig =
+          variant.hasProperty("testedVariant") ?
+            variant.testedVariant.compileConfiguration.incoming.artifactView {
+                attributes {
+                    it.attribute(artifactType, "jar")
+                }
+            }.files : null
+      setupExtractIncludeProtosTask(generateProtoTask, variant.name, classPathConfig, testClassPathConfig)
+
+      // ExtractProto task, one per source set.
       if (project.android.hasProperty('libraryVariants')) {
+          // Include source proto files in the compiled archive, so that proto files from
+          // dependent projects can import them.
           Task processResourcesTask = variant.getProcessJavaResourcesProvider().get()
           processResourcesTask.from(generateProtoTask.sourceFiles) {
               include '**/*.proto'
           }
           variant.sourceSets.each {
-              setupExtractIncludeProtosTask(generateProtoTask, it.name)
               Task extractTask = setupExtractProtosTask(generateProtoTask, it.name)
               processResourcesTask.dependsOn(extractTask)
           }
       } else {
           variant.sourceSets.each {
-              setupExtractIncludeProtosTask(generateProtoTask, it.name)
               setupExtractProtosTask(generateProtoTask, it.name)
           }
       }
@@ -384,7 +412,7 @@ class ProtobufPlugin implements Plugin<Project> {
             // dependencies.
             if (Utils.isTest(sourceSetOrVariantName)) {
               inputFiles.from getSourceSets()['main'].proto
-              inputFiles.from testedCompileClasspathConfiguration ?: project.configurations['compile']
+              inputFiles.from testedCompileClasspathConfiguration
             }
           } else {
             // In Java projects, the compileClasspath of the 'test' sourceSet includes all the

src/test/groovy/com/google/protobuf/gradle/ProtobufAndroidPluginTest.groovy

@@ -110,6 +110,37 @@ class ProtobufAndroidPluginTest extends Specification {
     gradleVersion << GRADLE_VERSION.takeRight(1)
   }
 
+  @Unroll
+  void "testProjectAndroidDependent [android #agpVersion, gradle #gradleVersion, kotlin #kotlinVersion]"() {
+    given: "project from testProjectAndroidLibrary, testProjectAndroid"
+    File testProjectStaging = ProtobufPluginTestHelper.projectBuilder('testProject')
+            .copyDirs('testProjectBase', 'testProject')
+            .build()
+    File testProjectLibraryStaging = ProtobufPluginTestHelper.projectBuilder('testProjectAndroidLibrary')
+            .copyDirs('testProjectAndroidLibrary')
+            .build()
+    File testProjectAndroidStaging = ProtobufPluginTestHelper.projectBuilder('testProjectAndroid')
+            .copyDirs('testProjectAndroidDependentBase', 'testProjectAndroid')
+            .build()
+    File mainProjectDir = ProtobufPluginTestHelper.projectBuilder('testProjectAndroidDependentMain')
+            .copySubProjects(testProjectStaging, testProjectLibraryStaging, testProjectAndroidStaging)
+            .withAndroidPlugin(agpVersion)
+            .build()
+    when: "build is invoked"
+    BuildResult result = buildAndroidProject(
+            mainProjectDir,
+            gradleVersion,
+            "testProjectAndroid:build"
+    )
+
+    then: "it succeed"
+    result.task(":testProjectAndroid:build").outcome == TaskOutcome.SUCCESS
+
+    where:
+    agpVersion << ANDROID_PLUGIN_VERSION
+    gradleVersion << GRADLE_VERSION
+  }
+
   @Unroll
   void "testProjectAndroidKotlin [android #agpVersion, gradle #gradleVersion, kotlin #kotlinVersion]"() {
     given: "project from testProject, testProjectLite & testProjectAndroid"

testProjectAndroid/src/androidTest/java/io/grpc/helloworldexample/TestLibrary.java

@@ -9,7 +9,7 @@ public class TestLibrary {
   // From src/main/proto/helloworld.proto
   Helloworld.HelloRequest request;
 
-  // From testProjectLite: src/nano/proto/messages.proto
+  // From dependency project (testProjectLite/testProjectAndroidLibrary): src/proto/messages.proto
   io.grpc.testing.Messages.SimpleRequest simpleRequest;
 
   // From lib/protos.jar

testProjectAndroid/src/test/java/io/grpc/helloworldexample/UnitTest.java

@@ -15,7 +15,7 @@ public final class UnitTest {
   // From src/main/proto/helloworld.proto
   private Helloworld.HelloRequest request;
 
-  // From testProjectLite: src/nano/proto/messages.proto
+  // From dependency project (testProjectLite/testProjectAndroidLibrary): src/proto/messages.proto
   private io.grpc.testing.Messages.SimpleRequest simpleRequest;
 
   // From lib/protos.jar