binder: add a jacocoTestReport task and include it with "all" coverage

Author: jdcormie

all/build.gradle

@@ -10,6 +10,7 @@ description = "gRPC: All"
 def subprojects = [
     project(':grpc-api'),
     project(':grpc-auth'),
+    findProject(':grpc-binder'), // Optional, to tolerate -PskipAndroid.
     project(':grpc-core'),
     project(':grpc-grpclb'),
     project(':grpc-gcp-csm-observability'),
@@ -27,7 +28,7 @@ def subprojects = [
     project(':grpc-testing'),
     project(':grpc-util'),
     project(':grpc-xds'),
-]
+].findAll { it != null }
 
 for (subproject in subprojects) {
     if (subproject == project) {
@@ -38,7 +39,7 @@ for (subproject in subprojects) {
 evaluationDependsOn(':grpc-interop-testing')
 
 dependencies {
-    api subprojects.minus([project(':grpc-protobuf-lite')])
+    api subprojects.minus([project(':grpc-protobuf-lite'), findProject(':grpc-binder')].findAll { it != null })
     implementation libraries.guava.jre // JRE required by transitive protobuf-java-util
 }
 
@@ -73,7 +74,17 @@ tasks.named("jacocoTestReport").configure {
 }
 
 coveralls {
-    sourceDirs = subprojects.sourceSets.main.allSource.srcDirs.flatten()
+    // Collect source directories from all subprojects to report to Coveralls.
+    // Android and Java projects have different ways of exposing their source directories.
+    sourceDirs = subprojects.collectMany { subproject ->
+        if (subproject.plugins.hasPlugin("java")) {
+            subproject.sourceSets.main.allSource.srcDirs
+        } else if (subproject.plugins.hasPlugin("com.android.library")) {
+            subproject.android.sourceSets.main.java.srcDirs
+        } else {
+            []
+        }
+    }
 }
 
 tasks.named("coveralls").configure { dependsOn tasks.named("jacocoTestReport") }

binder/build.gradle

@@ -20,6 +20,13 @@ android {
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
     lintOptions { abortOnError = false }
+    buildTypes {
+        debug {
+            testCoverageEnabled true // For robolectric unit tests.
+            enableUnitTestCoverage true // For tests that run on an emulator.
+        }
+    }
+
     publishing {
         singleVariant('release') {
             withSourcesJar()
@@ -133,3 +140,31 @@ afterEvaluate {
     components.release.withVariantsFromConfiguration(configurations.releaseTestFixturesVariantReleaseApiPublication) { skip() }
     components.release.withVariantsFromConfiguration(configurations.releaseTestFixturesVariantReleaseRuntimePublication) { skip() }
 }
+
+tasks.withType(Test) {
+    // Robolectric modifies classes in memory at runtime, so they lack a java.security.CodeSource
+    // URL to their on-disk location. By default, JaCoCo ignores classes without this property.
+    // Overriding this allows Robolectric tests to be instrumented.
+    jacoco.includeNoLocationClasses = true
+    // Don't instrument certain JDK internals protected from modification by JEP 403's "strong
+    // encapsulation." Avoids IllegalAccessError, InvalidClassException and similar at runtime.
+    jacoco.excludes = ["jdk.internal.**"]
+}
+
+// Android projects don't automatically get a coverage report task. We must
+// register one manually here and wire it up to AGP's test tasks.
+tasks.register("jacocoTestReport", JacocoReport) {
+    dependsOn "testDebugUnitTest"
+
+    reports {
+        // For codecov.io and coveralls.
+        xml.required = true
+        // Use the same output location as the other subprojects.
+        html.outputLocation = layout.buildDirectory.dir("reports/jacoco/test/html")
+    }
+
+    sourceDirectories.from = android.sourceSets.main.java.srcDirs
+    classDirectories.from = fileTree(dir: layout.buildDirectory.dir("intermediates/javac/debug/classes"),
+            excludes: ['**/R.class', '**/R$*.class', '**/BuildConfig.class', '**/Manifest*.*', '**/*Test*.*', 'android/**/*.*'])
+    executionData.from = tasks.named("testDebugUnitTest").map { it.jacoco.destinationFile }
+}