jacoco.config.gradle

// filter of files that shouldn't be part of the report
def androidFileFilter =
        [ //jdk
          'jdk.internal.*',
          // data binding
          '**/databinding/*.class',
          '**/BR.*',
          // android
          '**/R.class',
          '**/R$*.class',
          '**/BuildConfig.*',
          '**/Manifest*.*',
          '**/*Test*.*',
          'android/**/*.*',
          // kotlin
          '**/META-INF/*',
          '**/*MapperImpl*.*',
          '**/*$ViewInjector*.*',
          '**/*$ViewBinder*.*',
          '**/BuildConfig.*',
          '**/*Component*.*',
          '**/*BR*.*',
          '**/Manifest*.*',
          '**/*$Lambda$*.*',
          '**/*Companion*.*',
          '**/*Module*.*',
          '**/*Dagger*.*',
          '**/*Hilt*.*',
          '**/*MembersInjector*.*',
          '**/*_MembersInjector.class',
          '**/*_Factory*.*',
          '**/*_Provide*Factory*.*',
          '**/*Extensions*.*',
          // sealed and data classes
          '**/*$Result.*',
          '**/*$Result$*.*',
          // adapters generated by moshi
          '**/*JsonAdapter.*',
          // room
          '**/*_Impl.class',
          '**/*_Impl*.*',
          // hilt
          '**/hilt_aggregated_deps/*'
        ]


/ **
  * Setup Jacoco for Android module.
  * - applies Plugin to the module.
  * - sets up the "debug" build type for jacoco 
  * - creates tasks:
  *     - if androidTest folder exists creates a jacocoAndroidTestReport alias for the jacoco coverageReport, otherwise an empty task.
  *     - if test folder exists creates a jacocoUnitTestReport alias for the jacoco coverageReport, otherwise an empty task.
  *     - creates jacocoTestReport which runs both alias tasks created before.
  *
  *  Note: "jacocoTestReport" is the task name which is default for Java Modules. 
  * /

def setupAndroidJacoco(Project module, ArrayList<String> fileFilter, String jacocoVersion) {
    configure(module) {
        apply plugin: "jacoco"

        module.android.testOptions.unitTests.all {
            jacoco.includeNoLocationClasses = true
            jacoco.excludes = fileFilter
        }
        // on API 21 enableAndroidTestCoverage makes the tests crash with resource not found issue
        def disableAndroidTestCoverage = findProperty("disableAndroidTestCoverage") ?: false
        android.buildTypes.debug.enableAndroidTestCoverage = !disableAndroidTestCoverage
        android.buildTypes.debug.enableUnitTestCoverage = true

        jacoco.toolVersion = "$jacocoVersion"

        def hasAndroidTests = new File("${module.projectDir}/src/androidTest").exists()
        def hasUnitTests = new File("${module.projectDir}/src/test").exists()
        if (hasUnitTests) {
            task jacocoUnitTestReport(dependsOn: ["createDebugUnitTestCoverageReport"]) {
                group = "verification"
            }
        } else {
            task jacocoUnitTestReport() {
                group = "verification"
            }
        }
        if (hasAndroidTests) {
            task jacocoAndroidTestReport(dependsOn: ["createDebugAndroidTestCoverageReport"]) {
                group = "verification"
            }
        } else {
            task jacocoAndroidTestReport() {
                group = "verification"
            }
        }

        task jacocoTestReport(dependsOn: ["jacocoUnitTestReport", "jacocoAndroidTestReport"]) {
            group = "verification"
        }
    }
}

/ **
  * Setup Jacoco for Java module.
  * - applies Plugin to the module.
  * - updates the  `jacocoTestReport` task to ignore the `androidFileFilter`
  * - ensures tests run before `jacocoTestReport`
  * /

def setupJavaJacoco(Project module, ArrayList<String> fileFilter) {
    configure(module) {
        apply plugin: "jacoco"

        jacocoTestReport {
            dependsOn test // tests are required to run before generating the report

            afterEvaluate {
                classDirectories.setFrom(files(classDirectories.files.collect {
                    fileTree(dir: it, exclude: fileFilter)
                }))
            }
        }
    }
}

/ **
  * Setup Jacoco for submodules based on their android or java module type 
  */
subprojects { module ->
    plugins.withType(JavaPlugin).whenPluginAdded {
        setupJavaJacoco(module, androidFileFilter)
    }

    plugins.withId("com.android.application") {
        setupAndroidJacoco(module, androidFileFilter, "$jacoco_version")
    }

    plugins.withId("com.android.library") {
        setupAndroidJacoco(module, androidFileFilter, "$jacoco_version")
    }
}

/ **
  * Setup Aggregation tasks for Jacoco.
  * - jacocoRootReport: can be used to generate the report after submodules `jacocoTestReport` has been ran at least once.
  * - runTestAndJacocoRootReport: calls the `jacocoTestReport` of each submodule then calls `jacocoRootReport` for aggregation.
  *
  * Context, how the aggregated report works:
  * The jacoco tasks created by the plugin generate .ec and .exec Execution-Data files in specific locations.
  * - These Execution-Data files are all pulled into one `JacocoReport` task (`executionData.from`).
  * - All the source files from all the submodules are pulled into the same `JacocoReport` task (`sourceDirectories.from`)
  * - All the class files from all the submodules are pulled into the same `JacocoReport` task (`classDirectories.from`)
  * Then finally the report is configured to be generated at root `build\coverage-report`
  * /
configure(rootProject) {
    apply plugin: "jacoco"
    def testTypeName = "debug"

    task runTestAndJacocoRootReport(type: JacocoReport, group: 'Coverage reports') {
        description = 'Run Tests and Generates report from all subprojects'

        // add all non empty subProjects `jacocoTestReport` task as a dependency.
        // note: these tasks are default Jacoco Task for Java and have been added above for Android modules.
        def codeProjects = subprojects.findAll({ it.subprojects.isEmpty() })
        codeProjects.forEach {
            dependsOn += ["$it.path:jacocoTestReport"]
        }

        finalizedBy("jacocoRootReport")
    }

    task jacocoRootReport(type: JacocoReport, group: 'Coverage reports') {
        description = 'Generates report from all subprojects'

        def codeProjects = subprojects.findAll({ it.subprojects.isEmpty() })
        sourceDirectories.from = files(codeProjects.collect { "${it.projectDir}/src/main/java" })

        def classFileTrees = codeProjects.collect {
            def javaClassFilesInJavaModuleTree = fileTree(
                    dir: "${it.buildDir}/classes/java/main",
                    excludes: androidFileFilter
            )
            def kotlinClassFilesInJavaModuleTree = fileTree(
                    dir: "${it.buildDir}/classes/kotlin/main",
                    excludes: androidFileFilter
            )
            def javaClassFilesInAndroidModuleTree = fileTree(
                    dir: "${it.buildDir}/intermediates/javac/${testTypeName}/classes",
                    excludes: androidFileFilter
            )
            def kotlinClassFilesInAndroidModuleTree = fileTree(
                    dir: "${it.buildDir}/tmp/kotlin-classes/${testTypeName}",
                    excludes: androidFileFilter
            )

            files([javaClassFilesInJavaModuleTree, kotlinClassFilesInJavaModuleTree, javaClassFilesInAndroidModuleTree, kotlinClassFilesInAndroidModuleTree])
        }.flatten()
        classDirectories.from = files(classFileTrees)

        def executionDataFiles = codeProjects.collect {
            def androidTestExecutionData = fileTree(
                    dir: "${it.buildDir}/outputs/code_coverage/${testTypeName}AndroidTest/connected/",
                    includes: ["**/*.ec", "**/*.exec"]
            )
            def androidUnitTestExecutionData = fileTree(
                    dir: "${it.buildDir}/outputs/unit_test_code_coverage/",
                    includes: ["**/*.ec", "**/*.exec"]
            )
            def javaUnitTestExecutionData = "${it.buildDir}/jacoco/test.exec"

            [androidTestExecutionData, androidUnitTestExecutionData, javaUnitTestExecutionData]
        }.flatten()
        executionData.from = files(executionDataFiles)

        reports {
            html {
                required = true
                destination file("${buildDir}/coverage-report")
            }
        }
    }
}