Rework dokka configuration and Gradle plugin

9 files changed, 221 insertions, 288 deletions

diff --git a/runners/cli/src/main/kotlin/cli/main.kt b/runners/cli/src/main/kotlin/cli/main.kt
index be42bc79..d217f83e 100644
--- a/runners/cli/src/main/kotlin/cli/main.kt
+++ b/runners/cli/src/main/kotlin/cli/main.kt
@@ -35,24 +35,22 @@ open class GlobalArguments(parser: DokkaArgumentsParser) : DokkaConfiguration {
         }
     }
 
-    override val generateIndexPages: Boolean by parser.singleFlag(
-        listOf("-generateIndexPages"),
-        "Generate index page"
-    )
-
     override val cacheRoot: String? by parser.stringOption(
         listOf("-cacheRoot"),
         "Path to cache folder, or 'default' to use ~/.cache/dokka, if not provided caching is disabled",
         null
     )
 
-    override val impliedPlatforms: List<String> = emptyList()
+    override val offlineMode: Boolean by parser.singleFlag(
+        listOf("-offlineMode"),
+        "Offline mode (do not download package lists from the Internet)"
+    )
 
     override val passesConfigurations: List<Arguments> by parser.repeatableFlag(
         listOf("-pass"),
         "Single dokka pass"
     ) {
-        Arguments(parser).also { if(it.moduleName.isEmpty()) DokkaConsoleLogger.warn("Not specified module name. It can result in unexpected behaviour while including documentation for module") }
+        Arguments(parser).also { if (it.moduleName.isEmpty()) DokkaConsoleLogger.warn("Not specified module name. It can result in unexpected behaviour while including documentation for module") }
     }
 
     override val modules: List<DokkaConfiguration.DokkaModuleDescription> = emptyList()
@@ -67,12 +65,17 @@ class Arguments(val parser: DokkaArgumentsParser) : DokkaConfiguration.PassConfi
         ""
     )
 
-    override val sourceSetName: String by parser.stringOption(
-        listOf("-sourceSetName"),
-        "Name of the source set",
-        "main"
+    override val displayName: String by parser.stringOption(
+        listOf("-displayName"),
+        "Name displayed in the generated documentation",
+        ""
     )
 
+    override val sourceSetID: String by parser.stringOption(
+        listOf("-sourceSetID"),
+        "Source set ID used for declaring dependent source sets",
+        "main"
+    )
 
     override val classpath: List<String> by parser.repeatableOption<String>(
         listOf("-classpath"),
@@ -84,11 +87,6 @@ class Arguments(val parser: DokkaArgumentsParser) : DokkaConfiguration.PassConfi
         "Source file or directory (allows many paths separated by the system path separator)"
     ) { SourceRootImpl(it) }
 
-    override val dependentSourceRoots: List<DokkaConfiguration.SourceRoot> by parser.repeatableOption(
-        listOf("-dependentRoots"),
-        "Source roots of dependent source sets"
-    ) { SourceRootImpl(it) }
-
     override val dependentSourceSets: List<String> by parser.repeatableOption<String>(
         listOf("-dependentSets"),
         "Names of dependent source sets"
@@ -163,16 +161,6 @@ class Arguments(val parser: DokkaArgumentsParser) : DokkaConfiguration.PassConfi
         ""
     )
 
-    override val sinceKotlin: String? by parser.stringOption(
-        listOf("-sinceKotlin"),
-        "Kotlin Api version to use as base version, if none specified",
-        null
-    )
-
-    override val collectInheritedExtensionsFromLibraries: Boolean by parser.singleFlag(
-        listOf("-collectInheritedExtensionsFromLibraries"),
-        "Search for applicable extensions in libraries"
-    )
 
     override val analysisPlatform: Platform by parser.singleOption(
         listOf("-analysisPlatform"),
@@ -181,10 +169,6 @@ class Arguments(val parser: DokkaArgumentsParser) : DokkaConfiguration.PassConfi
         { Platform.DEFAULT }
     )
 
-    override val targets: List<String> by parser.repeatableOption<String>(
-        listOf("-target"),
-        "Generation targets"
-    )
 
     override val perPackageOptions: MutableList<DokkaConfiguration.PackageOptions> by parser.singleOption(
         listOf("-packageOptions"),
@@ -215,16 +199,16 @@ class Arguments(val parser: DokkaArgumentsParser) : DokkaConfiguration.PassConfi
 object MainKt {
     fun defaultLinks(config: DokkaConfiguration.PassConfiguration): MutableList<ExternalDocumentationLink> =
         mutableListOf<ExternalDocumentationLink>().apply {
-        if (!config.noJdkLink)
-            this += DokkaConfiguration.ExternalDocumentationLink
-                .Builder("https://docs.oracle.com/javase/${config.jdkVersion}/docs/api/")
-                .build()
-
-        if (!config.noStdlibLink)
-            this += DokkaConfiguration.ExternalDocumentationLink
-                .Builder("https://kotlinlang.org/api/latest/jvm/stdlib/")
-                .build()
-    }
+            if (!config.noJdkLink)
+                this += DokkaConfiguration.ExternalDocumentationLink
+                    .Builder("https://docs.oracle.com/javase/${config.jdkVersion}/docs/api/")
+                    .build()
+
+            if (!config.noStdlibLink)
+                this += DokkaConfiguration.ExternalDocumentationLink
+                    .Builder("https://kotlinlang.org/api/latest/jvm/stdlib/")
+                    .build()
+        }
 
     fun parseLinks(links: String): List<ExternalDocumentationLink> {
         val (parsedLinks, parsedOfflineLinks) = links.split("^^")
diff --git a/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/ConfigurationExtractor.kt b/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/ConfigurationExtractor.kt
index c69c6f67..44a0635f 100644
--- a/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/ConfigurationExtractor.kt
+++ b/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/ConfigurationExtractor.kt
@@ -1,9 +1,5 @@
 package org.jetbrains.dokka.gradle
 
-import com.android.build.gradle.*
-import com.android.build.gradle.api.BaseVariant
-import com.android.builder.core.BuilderConstants
-import org.gradle.api.NamedDomainObjectCollection
 import org.gradle.api.Project
 import org.gradle.api.Task
 import org.gradle.api.UnknownDomainObjectException
@@ -13,57 +9,60 @@ import org.gradle.api.plugins.JavaPluginConvention
 import org.gradle.api.tasks.SourceSet
 import org.gradle.api.tasks.compile.AbstractCompile
 import org.jetbrains.dokka.ReflectDsl
-import org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
 import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension
 import org.jetbrains.kotlin.gradle.dsl.KotlinProjectExtension
 import org.jetbrains.kotlin.gradle.dsl.KotlinSingleTargetExtension
-import org.jetbrains.kotlin.gradle.plugin.*
+import org.jetbrains.kotlin.gradle.plugin.KotlinCompilation
+import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 import java.io.File
 import java.io.Serializable
 
 class ConfigurationExtractor(private val project: Project) {
 
-    fun extractConfiguration(targetName: String, variantName: String?) =
-        extractFromKotlinProject(targetName, variantName)
-
-    fun extractFromKotlinProject(sourceSetName: String, variantName: String?): PlatformData? {
+    fun extractConfiguration(sourceSetName: String): PlatformData? {
         val projectExtension = project.extensions.getByType(KotlinProjectExtension::class.java)
         val sourceSet = projectExtension.sourceSets.findByName(sourceSetName)
             ?: run { project.logger.error("No source set with name '$sourceSetName' found"); return null }
         val compilation = when (projectExtension) {
-            is KotlinMultiplatformExtension -> projectExtension.targets.flatMap { it.compilations }
-                .find { it.kotlinSourceSets.contains(sourceSet) }
+            is KotlinMultiplatformExtension -> {
+                val targets = projectExtension.targets.flatMap { it.compilations }
+                targets.find { it.name == sourceSetName } ?: targets.find { it.kotlinSourceSets.contains(sourceSet) }
+            }
             is KotlinSingleTargetExtension -> projectExtension.target.compilations.find {
                 it.kotlinSourceSets.contains(sourceSet)
             }
             else -> null
-        } ?: run { project.logger.error("No compilation found for set with name '$sourceSetName'"); return null }
+        }
+
+        val sourceRoots = sourceSet.sourceFiles
+        val classpath = compilation?.classpath
+            ?: sourceRoots + sourceSet.allParentSourceFiles()
 
-        val classpath = compilation.compileDependencyFiles.files.filter { it.exists() }
-        val dependencies = (compilation.allKotlinSourceSets - sourceSet).flatMap { it.kotlin.sourceDirectories }
         return PlatformData(
             sourceSetName,
-            classpath,
-            sourceSet.kotlin.sourceDirectories.filter { it.exists() }.toList(),
-            dependencies,
-            sourceSet.dependsOn.map {  it.name },
-            compilation.target.targetName
+            classpath.filter { it.exists() },
+            sourceRoots,
+            sourceSet.dependsOn.map { it.name },
+            compilation?.target?.platformType?.name ?: "common"
         )
     }
 
+    private fun KotlinSourceSet.allParentSourceFiles(): List<File> =
+        sourceFiles + dependsOn.flatMap { it.allParentSourceFiles() }
+
     fun extractFromJavaPlugin(): PlatformData? =
         project.convention.findPlugin(JavaPluginConvention::class.java)
             ?.run { sourceSets.findByName(SourceSet.MAIN_SOURCE_SET_NAME)?.allSource?.srcDirs }
-            ?.let { PlatformData(null, emptyList(), it.toList(), emptyList(), emptyList(), "") }
+            ?.let { PlatformData(null, emptyList(), it.toList(), emptyList(), "") }
 
-    fun extractFromKotlinTasks(passName: String, kotlinTasks: List<Task>): PlatformData? =
+    fun extractFromKotlinTasks(kotlinTasks: List<Task>): List<PlatformData> =
         try {
-            kotlinTasks.find { it.toString() == passName }?.let { extractFromKotlinTask(it) }
+            kotlinTasks.map { extractFromKotlinTask(it) }
         } catch (e: Throwable) {
             when (e) {
                 is UnknownDomainObjectException, is NoClassDefFoundError, is ClassNotFoundException ->
-                    extractFromKotlinTasksTheHardWay(passName, kotlinTasks)
+                    listOfNotNull(extractFromKotlinTasksTheHardWay(kotlinTasks))
                 else -> throw e
             }
         }
@@ -80,18 +79,17 @@ class ConfigurationExtractor(private val project: Project) {
                         .flatMap { it.compilations }.firstOrNull { it.compileKotlinTask == task }
                 else -> throw e
             }
-        }.let {
+        }.let { compilation ->
             PlatformData(
                 task.name,
-                getClasspath(it),
-                getSourceSet(it),
-                getDependentSourceSetRoots(it),
-                getDependentSourceSet(it).map { it.name },
-                it?.platformType?.toString() ?: ""
+                compilation?.classpath.orEmpty(),
+                compilation?.sourceFiles.orEmpty(),
+                compilation?.dependentSourceSets?.map { it.name }.orEmpty(),
+                compilation?.platformType?.toString() ?: ""
             )
         }
 
-    private fun extractFromKotlinTasksTheHardWay(passName: String, kotlinTasks: List<Task>): PlatformData? {
+    private fun extractFromKotlinTasksTheHardWay(kotlinTasks: List<Task>): PlatformData? {
         val allClasspath = mutableSetOf<File>()
         var allClasspathFileCollection: FileCollection = project.files()
         val allSourceRoots = mutableSetOf<File>()
@@ -128,93 +126,41 @@ class ConfigurationExtractor(private val project: Project) {
         }
         classpath.addAll(project.files(allClasspath).toList())
 
-        return PlatformData(null, classpath, allSourceRoots.toList(), emptyList(), emptyList(),"")
+        return PlatformData(null, classpath, allSourceRoots.toList(), emptyList(), "")
     }
 
-    private fun getSourceSet(target: KotlinTarget, variantName: String? = null): List<File> =
-        if (variantName != null)
-            getSourceSet(getCompilation(target, variantName))
-        else
-            getSourceSet(getMainCompilation(target))
-
-    private fun getClasspath(target: KotlinTarget, variantName: String? = null): List<File> =
-        if (target.isAndroidTarget()) {
-            if (variantName != null)
-                getClasspathFromAndroidTask(getCompilation(target, variantName))
-            else
-                getClasspathFromAndroidTask(getMainCompilation(target))
-        } else {
-            getClasspath(getMainCompilation(target))
-        }
-
-    private fun getSourceSet(compilation: KotlinCompilation<*>?): List<File> = compilation
-        ?.kotlinSourceSets
-        ?.flatMap { it.kotlin.sourceDirectories }
-        ?.filter { it.exists() }
-        .orEmpty()
+    private val KotlinCompilation<*>.sourceFiles: List<File>
+        get() = kotlinSourceSets.flatMap { it.sourceFiles }
 
-    private fun getDependentSourceSet(compilation: KotlinCompilation<*>?) = compilation
-        ?.let { it.allKotlinSourceSets - it.kotlinSourceSets }.orEmpty()
+    private val KotlinSourceSet.sourceFiles: List<File>
+        get() = kotlin.sourceDirectories.filter { it.exists() }.toList()
 
-    private fun getDependentSourceSetRoots(compilation: KotlinCompilation<*>?): List<File> =
-        getDependentSourceSet(compilation)?.flatMap { it.kotlin.sourceDirectories }
-        .filter { it.exists() }
+    private val KotlinCompilation<*>.dependentSourceSets: Set<KotlinSourceSet>
+        get() = (allKotlinSourceSets - kotlinSourceSets)
 
-    private fun getClasspath(compilation: KotlinCompilation<*>?): List<File> = compilation
-        ?.compileDependencyFiles
-        ?.files
-        ?.toList()
-        ?.filter { it.exists() }
-        .orEmpty()
+    private val KotlinCompilation<*>.classpath: List<File>
+        get() = if (target.isAndroidTarget()) {
+            getClasspathFromAndroidTask(this)
+        } else {
+            getClasspathFromRegularTask(this)
+        }
 
     // This is a workaround for KT-33893
     private fun getClasspathFromAndroidTask(compilation: KotlinCompilation<*>): List<File> = (compilation
         .compileKotlinTask as? KotlinCompile)
-        ?.classpath?.files?.toList() ?: getClasspath(compilation)
-
-    private fun getMainCompilation(target: KotlinTarget) =
-        getCompilation(target, getMainCompilationName(target))
-
-    private fun getCompilation(target: KotlinTarget, name: String) =
-        target.compilations.getByName(name)
-
-    private fun getMainCompilationName(target: KotlinTarget) = if (target.isAndroidTarget())
-        getVariants(project).filter { it.buildType.name == BuilderConstants.RELEASE }.map { it.name }.first()
-    else
-        KotlinCompilation.MAIN_COMPILATION_NAME
-
-    private fun getVariants(project: Project): Set<BaseVariant> {
-        val androidExtension = project.extensions.getByName("android")
-        val baseVariants = when (androidExtension) {
-            is AppExtension -> androidExtension.applicationVariants.toSet()
-            is LibraryExtension -> {
-                androidExtension.libraryVariants.toSet() +
-                        if (androidExtension is FeatureExtension) {
-                            androidExtension.featureVariants.toSet()
-                        } else {
-                            emptySet<BaseVariant>()
-                        }
-            }
-            is TestExtension -> androidExtension.applicationVariants.toSet()
-            else -> emptySet()
-        }
-        val testVariants = if (androidExtension is TestedExtension) {
-            androidExtension.testVariants.toSet() + androidExtension.unitTestVariants.toSet()
-        } else {
-            emptySet<BaseVariant>()
-        }
-
-        return baseVariants + testVariants
-    }
+        ?.classpath?.files?.toList() ?: getClasspathFromRegularTask(compilation)
 
-    private fun getPlatformName(platform: KotlinPlatformType): String =
-        if (platform == KotlinPlatformType.androidJvm) KotlinPlatformType.jvm.toString() else platform.toString()
+    private fun getClasspathFromRegularTask(compilation: KotlinCompilation<*>): List<File> =
+        compilation
+            .compileDependencyFiles
+            .files
+            .toList()
+            .filter { it.exists() }
 
     data class PlatformData(
         val name: String?,
         val classpath: List<File>,
         val sourceRoots: List<File>,
-        val dependentSourceRoots: List<File>,
         val dependentSourceSets: List<String>,
         val platform: String
     ) : Serializable
diff --git a/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaCollectorTask.kt b/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaCollectorTask.kt
index f4fa7aaa..8c4e0c4c 100644
--- a/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaCollectorTask.kt
+++ b/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaCollectorTask.kt
@@ -20,7 +20,7 @@ open class DokkaCollectorTask : DefaultTask() {
 
     @TaskAction
     fun collect() {
-        val passesConfigurations = getProjects(project).filter { it.name in modules }.map {
+        val passesConfigurations = getProjects(project).filter { it.name in modules }.mapNotNull {
             val task = try {
                 it.tasks.getByName(DOKKA_TASK_NAME, DokkaTask::class)
             } catch (e: UnknownTaskException) {
@@ -33,12 +33,11 @@ open class DokkaCollectorTask : DefaultTask() {
             outputDir = outputDirectory
             cacheRoot = passesConfigurations.first().cacheRoot
             format = passesConfigurations.first().format
-            generateIndexPages = passesConfigurations.first().generateIndexPages
         }
 
         configuration = passesConfigurations.fold(initial) { acc, it: GradleDokkaConfigurationImpl ->
-            if(acc.format != it.format || acc.generateIndexPages != it.generateIndexPages || acc.cacheRoot != it.cacheRoot)
-                throw IllegalStateException("Dokka task configurations differ on core arguments (format, generateIndexPages, cacheRoot)")
+            if(acc.format != it.format || acc.cacheRoot != it.cacheRoot)
+                throw IllegalStateException("Dokka task configurations differ on core arguments (format, cacheRoot)")
             acc.passesConfigurations = acc.passesConfigurations + it.passesConfigurations
             acc.pluginsClasspath = (acc.pluginsClasspath + it.pluginsClasspath).distinct()
             acc
diff --git a/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaMultimoduleTask.kt b/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaMultimoduleTask.kt
index a1bfdb96..2ef85de2 100644
--- a/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaMultimoduleTask.kt
+++ b/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaMultimoduleTask.kt
@@ -35,9 +35,9 @@ open class DokkaMultimoduleTask : DefaultTask(), Configurable {
         System.setProperty(DokkaTask.COLORS_ENABLED_PROPERTY, "false")
 
         try {
-            loadFatJar()
+            loadCore()
             val bootstrapClass =
-                ClassloaderContainer.fatJarClassLoader!!.loadClass("org.jetbrains.dokka.DokkaMultimoduleBootstrapImpl")
+                ClassloaderContainer.coreClassLoader!!.loadClass("org.jetbrains.dokka.DokkaMultimoduleBootstrapImpl")
             val bootstrapInstance = bootstrapClass.constructors.first().newInstance()
             val bootstrapProxy: DokkaBootstrap = automagicTypedProxy(
                 javaClass.classLoader,
@@ -85,10 +85,10 @@ open class DokkaMultimoduleTask : DefaultTask(), Configurable {
                 }
         }
 
-    private fun loadFatJar() {
-        if (ClassloaderContainer.fatJarClassLoader == null) {
+    private fun loadCore() {
+        if (ClassloaderContainer.coreClassLoader == null) {
             val jars = dokkaRuntime!!.resolve()
-            ClassloaderContainer.fatJarClassLoader = URLClassLoader(
+            ClassloaderContainer.coreClassLoader = URLClassLoader(
                 jars.map { it.toURI().toURL() }.toTypedArray(),
                 ClassLoader.getSystemClassLoader().parent
             )
diff --git a/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaTask.kt b/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaTask.kt
index 2de95493..5a420d4d 100644
--- a/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaTask.kt
+++ b/runners/gradle-plugin/src/main/kotlin/org/jetbrains/dokka/gradle/DokkaTask.kt
@@ -15,15 +15,16 @@ import org.jetbrains.dokka.ReflectDsl
 import org.jetbrains.dokka.ReflectDsl.isNotInstance
 import org.jetbrains.dokka.gradle.ConfigurationExtractor.PlatformData
 import org.jetbrains.dokka.plugability.Configurable
-import org.jetbrains.kotlin.gradle.plugin.KotlinPlatformType
 import java.io.File
 import java.net.URLClassLoader
 import java.util.concurrent.Callable
 import java.util.function.BiConsumer
+import kotlin.system.exitProcess
 
 open class DokkaTask : DefaultTask(), Configurable {
     private val ANDROID_REFERENCE_URL = Builder("https://developer.android.com/reference/").build()
     private val GLOBAL_CONFIGURATION_NAME = "global" // Used for copying perPackageOptions to other platforms
+    private val configExtractor = ConfigurationExtractor(project)
 
     @Suppress("MemberVisibilityCanBePrivate")
     fun defaultKotlinTasks(): List<Task> = with(ReflectDsl) {
@@ -57,8 +58,6 @@ open class DokkaTask : DefaultTask(), Configurable {
     var subProjects: List<String> = emptyList()
 
     @Input
-    var impliedPlatforms: MutableList<String> = arrayListOf()
-
     override val pluginsConfiguration: Map<String, String> = mutableMapOf()
 
     @Optional
@@ -66,54 +65,47 @@ open class DokkaTask : DefaultTask(), Configurable {
     var cacheRoot: String? = null
 
     @Classpath
-    lateinit var pluginsConfig: Configuration
+    lateinit var pluginsClasspathConfiguration: Configuration
 
     var dokkaSourceSets: NamedDomainObjectContainer<GradlePassConfigurationImpl>
         @Suppress("UNCHECKED_CAST")
         @Nested get() = (DslObject(this).extensions.getByName(SOURCE_SETS_EXTENSION_NAME) as NamedDomainObjectContainer<GradlePassConfigurationImpl>)
         internal set(value) = DslObject(this).extensions.add(SOURCE_SETS_EXTENSION_NAME, value)
 
-    var configuration: GradlePassConfigurationImpl
-        @Suppress("UNCHECKED_CAST")
-        @Nested get() = DslObject(this).extensions.getByType(GradlePassConfigurationImpl::class.java)
-        internal set(value) = DslObject(this).extensions.add(CONFIGURATION_EXTENSION_NAME, value)
-
-    var config: GradleDokkaConfigurationImpl? = null
-
-    // Configure Dokka with closure in Gradle Kotlin DSL
-    fun configuration(action: Action<in GradlePassConfigurationImpl>) = action.execute(configuration)
-
     private val kotlinTasks: List<Task> by lazy {
-        extractKotlinCompileTasks(
-            configuration.collectKotlinTasks ?: { defaultKotlinTasks() })
+        extractKotlinCompileTasks({
+            dokkaSourceSets.map {
+                it.collectKotlinTasks?.invoke()
+            }
+        }.takeIf { it().isNotEmpty() } ?: { defaultKotlinTasks() }
+        )
     }
 
-    private val configExtractor = ConfigurationExtractor(project)
-
     @Input
     var disableAutoconfiguration: Boolean = false
 
+    @Input
+    var offlineMode: Boolean = false
+
     private var outputDiagnosticInfo: Boolean =
         false // Workaround for Gradle, which fires some methods (like collectConfigurations()) multiple times in its lifecycle
 
-    private fun loadFatJar() {
-        if (ClassloaderContainer.fatJarClassLoader == null) {
+    private fun loadCore() {
+        if (ClassloaderContainer.coreClassLoader == null) {
             val jars = dokkaRuntime!!.resolve()
-            ClassloaderContainer.fatJarClassLoader = URLClassLoader(
+            ClassloaderContainer.coreClassLoader = URLClassLoader(
                 jars.map { it.toURI().toURL() }.toTypedArray(),
                 ClassLoader.getSystemClassLoader().parent
             )
         }
     }
 
-    private fun extractKotlinCompileTasks(collectTasks: () -> List<Any?>?): List<Task> {
+    protected fun extractKotlinCompileTasks(collectTasks: () -> List<Any?>?): List<Task> {
         val inputList = (collectTasks.invoke() ?: emptyList()).filterNotNull()
         val (paths, other) = inputList.partition { it is String }
 
-        val taskContainer = project.tasks
-
         val tasksByPath = paths.map {
-            taskContainer.findByPath(it as String) ?: throw IllegalArgumentException("Task with path '$it' not found")
+            project.tasks.findByPath(it as String) ?: throw IllegalArgumentException("Task with path '$it' not found")
         }
 
         other
@@ -134,7 +126,7 @@ open class DokkaTask : DefaultTask(), Configurable {
     private fun Iterable<String>.toProjects(): List<Project> =
         project.subprojects.toList().filter { this.contains(it.name) }
 
-    private fun collectSuppressedFiles(sourceRoots: List<SourceRoot>) =
+    protected open fun collectSuppressedFiles(sourceRoots: List<SourceRoot>) =
         if (project.isAndroidProject()) {
             val generatedRoot = project.buildDir.resolve("generated").absoluteFile
             sourceRoots
@@ -147,25 +139,21 @@ open class DokkaTask : DefaultTask(), Configurable {
         }
 
     @TaskAction
-    fun generate() {
-        generateForConfig(config ?: getConfiguration())
-    }
+    fun generate() = getConfiguration()?.let { generate(it) } ?: exitProcess(0)
 
-    internal fun generateForConfig(configuration: GradleDokkaConfigurationImpl) {
+    protected open fun generate(configuration: GradleDokkaConfigurationImpl) {
         outputDiagnosticInfo = true
         val kotlinColorsEnabledBefore = System.getProperty(COLORS_ENABLED_PROPERTY) ?: "false"
         System.setProperty(COLORS_ENABLED_PROPERTY, "false")
         try {
-            loadFatJar()
+            loadCore()
 
             val bootstrapClass =
-                ClassloaderContainer.fatJarClassLoader!!.loadClass("org.jetbrains.dokka.DokkaBootstrapImpl")
+                ClassloaderContainer.coreClassLoader!!.loadClass("org.jetbrains.dokka.DokkaBootstrapImpl")
             val bootstrapInstance = bootstrapClass.constructors.first().newInstance()
             val bootstrapProxy: DokkaBootstrap =
                 automagicTypedProxy(javaClass.classLoader, bootstrapInstance)
 
-            val gson = GsonBuilder().setPrettyPrinting().create()
-
             bootstrapProxy.configure(
                 BiConsumer { level, message ->
                     when (level) {
@@ -176,7 +164,7 @@ open class DokkaTask : DefaultTask(), Configurable {
                         "error" -> logger.error(message)
                     }
                 },
-                gson.toJson(configuration)
+                GsonBuilder().setPrettyPrinting().create().toJson(configuration)
             )
 
             bootstrapProxy.generate()
@@ -186,68 +174,78 @@ open class DokkaTask : DefaultTask(), Configurable {
         }
     }
 
-    internal fun getConfiguration(): GradleDokkaConfigurationImpl {
+    internal open fun getConfiguration(): GradleDokkaConfigurationImpl? {
         val globalConfig = dokkaSourceSets.toList().find { it.name.toLowerCase() == GLOBAL_CONFIGURATION_NAME }
-        val defaultModulesConfiguration = collectConfigurations()
-            .map { defaultPassConfiguration(it, globalConfig) }
+        val defaultModulesConfiguration = passConfigurations
+            .map { defaultPassConfiguration(it, globalConfig) }.takeIf { it.isNotEmpty() }
+            ?: listOf(
+                defaultPassConfiguration(
+                    collectSinglePassConfiguration(GradlePassConfigurationImpl("main")),
+                    null
+                )
+            ).takeIf { project.isNotMultiplatformProject() } ?: emptyList()
+
+        if (defaultModulesConfiguration.isEmpty()) {
+            logger.error("No source sets to document found, exiting")
+            return null
+        }
+
         return GradleDokkaConfigurationImpl().apply {
             outputDir = project.file(outputDirectory).absolutePath
             format = outputFormat
-            generateIndexPages = true
-            cacheRoot = cacheRoot
-            impliedPlatforms = impliedPlatforms
+            cacheRoot = this@DokkaTask.cacheRoot
+            offlineMode = this@DokkaTask.offlineMode
             passesConfigurations = defaultModulesConfiguration
-            pluginsClasspath = pluginsConfig.resolve().toList()
+            pluginsClasspath = pluginsClasspathConfiguration.resolve().toList()
             pluginsConfiguration = this@DokkaTask.pluginsConfiguration
         }
     }
 
-    private fun collectConfigurations() =
-        if (this.dokkaSourceSets.isNotEmpty()) collectMultipassConfiguration() else listOf(collectSinglePassConfiguration(configuration))
 
-    private fun collectMultipassConfiguration() = dokkaSourceSets
-        .filterNot { it.name.toLowerCase() == GLOBAL_CONFIGURATION_NAME }
-        .map { collectSinglePassConfiguration(it) }
+    protected val passConfigurations: List<GradlePassConfigurationImpl>
+        get() = dokkaSourceSets
+            .filterNot { it.name.toLowerCase() == GLOBAL_CONFIGURATION_NAME }
+            .map { collectSinglePassConfiguration(it) }
 
-    private fun collectSinglePassConfiguration(config: GradlePassConfigurationImpl): GradlePassConfigurationImpl {
+    protected fun collectSinglePassConfiguration(config: GradlePassConfigurationImpl): GradlePassConfigurationImpl {
         val userConfig = config
-        /*.let {
-            if (it.collectKotlinTasks != null) {
-                configExtractor.extractFromKotlinTasks(extractKotlinCompileTasks(it.collectKotlinTasks!!))
-                    ?.let { platformData -> mergeUserConfigurationAndPlatformData(it, platformData) } ?: it
-            } else {
-                it
+            .apply {
+                collectKotlinTasks?.let {
+                    configExtractor.extractFromKotlinTasks(extractKotlinCompileTasks(it))
+                        .fold(this) { config, platformData ->
+                            mergeUserConfigurationAndPlatformData(config, platformData)
+                        }
+                }
             }
-        }*/
 
         if (disableAutoconfiguration) return userConfig
 
-        val baseConfig = configExtractor.extractConfiguration(userConfig.name, userConfig.androidVariant)
+        val baseConfig = configExtractor.extractConfiguration(userConfig.name)
             ?.let { mergeUserConfigurationAndPlatformData(userConfig, it) }
             ?: if (this.dokkaSourceSets.isNotEmpty()) {
                 if (outputDiagnosticInfo)
                     logger.warn(
-                        "Could not find target with name: ${userConfig.name} in Kotlin Gradle Plugin, " +
-                                "using only user provided configuration for this target"
+                        "Could not find source set with name: ${userConfig.name} in Kotlin Gradle Plugin, " +
+                                "using only user provided configuration for this source set"
                     )
                 userConfig
             } else {
-                logger.warn("Could not find target with name: ${userConfig.name} in Kotlin Gradle Plugin")
-                collectFromSinglePlatformOldPlugin(userConfig.name)
+                if (outputDiagnosticInfo)
+                    logger.warn("Could not find source set with name: ${userConfig.name} in Kotlin Gradle Plugin")
+                collectFromSinglePlatformOldPlugin(userConfig.name, userConfig)
             }
 
         return if (subProjects.isNotEmpty()) {
             try {
-                subProjects.toProjects().fold(baseConfig) { config, subProject ->
+                subProjects.toProjects().fold(baseConfig) { configAcc, subProject ->
                     mergeUserConfigurationAndPlatformData(
-                        config,
-                        ConfigurationExtractor(subProject).extractConfiguration(config.name, config.androidVariant)!!
+                        configAcc,
+                        ConfigurationExtractor(subProject).extractConfiguration(userConfig.name)!!
                     )
                 }
             } catch (e: NullPointerException) {
                 logger.warn(
-                    "Cannot extract sources from subProjects. Do you have the Kotlin plugin in version 1.3.30+ " +
-                            "and the Kotlin plugin applied in the root project?"
+                    "Cannot extract sources from subProjects. Do you have the Kotlin plugin applied in the root project?"
                 )
                 baseConfig
             }
@@ -256,49 +254,52 @@ open class DokkaTask : DefaultTask(), Configurable {
         }
     }
 
-    private fun collectFromSinglePlatformOldPlugin(name: String) =
-        configExtractor.extractFromKotlinTasks(name, kotlinTasks)
-            ?.let { mergeUserConfigurationAndPlatformData(configuration, it) }
+    protected fun collectFromSinglePlatformOldPlugin(name: String, userConfig: GradlePassConfigurationImpl) =
+        kotlinTasks.find { it.name == name }
+            ?.let { configExtractor.extractFromKotlinTasks(listOf(it)) }
+            ?.singleOrNull()
+            ?.let { mergeUserConfigurationAndPlatformData(userConfig, it) }
             ?: configExtractor.extractFromJavaPlugin()
-                ?.let { mergeUserConfigurationAndPlatformData(configuration, it) }
-            ?: configuration
+                ?.let { mergeUserConfigurationAndPlatformData(userConfig, it) }
+            ?: userConfig
 
-    private fun mergeUserConfigurationAndPlatformData(
+    protected fun mergeUserConfigurationAndPlatformData(
         userConfig: GradlePassConfigurationImpl,
         autoConfig: PlatformData
     ) =
         userConfig.copy().apply {
-            sourceSetName = autoConfig.name ?: ""
+            sourceSetID = autoConfig.name ?: ""
             sourceRoots.addAll(userConfig.sourceRoots.union(autoConfig.sourceRoots.toSourceRoots()).distinct())
-            dependentSourceRoots.addAll(userConfig.dependentSourceRoots.union(autoConfig.dependentSourceRoots.toSourceRoots()).distinct())
             dependentSourceSets.addAll(userConfig.dependentSourceSets.union(autoConfig.dependentSourceSets).distinct())
             classpath = userConfig.classpath.union(autoConfig.classpath.map { it.absolutePath }).distinct()
             if (userConfig.platform == null && autoConfig.platform != "")
                 platform = autoConfig.platform
         }
 
-    private fun defaultPassConfiguration(
+    protected fun defaultPassConfiguration(
         config: GradlePassConfigurationImpl,
         globalConfig: GradlePassConfigurationImpl?
     ): GradlePassConfigurationImpl {
-        if (config.moduleName == "") {
+        if (config.moduleName.isBlank()) {
             config.moduleName = project.name
         }
-        if (config.sourceSetName.isEmpty()) {
-            config.sourceSetName = config.name.substringBeforeLast("Main").takeIf(String::isNotBlank) ?: config.platform.toString()
+        if (config.sourceSetID.isBlank()) {
+            config.sourceSetID = config.name.takeIf(String::isNotBlank) ?: config.analysisPlatform.key
         }
-        config.classpath = (config.classpath as List<Any>).map { it.toString() }.distinct() // Workaround for Groovy's GStringImpl
+        config.displayName = config.sourceSetID.substringBeforeLast("Main")
+        config.classpath =
+            (config.classpath as List<Any>).map { it.toString() }.distinct() // Workaround for Groovy's GStringImpl
         config.sourceRoots = config.sourceRoots.distinct().toMutableList()
         config.samples = config.samples.map { project.file(it).absolutePath }
         config.includes = config.includes.map { project.file(it).absolutePath }
         config.suppressedFiles += collectSuppressedFiles(config.sourceRoots)
-        if (project.isAndroidProject() && !config.noAndroidSdkLink) { // TODO: introduce Android as a separate Dokka platform?
+        if (project.isAndroidProject() && !config.noAndroidSdkLink) {
             config.externalDocumentationLinks.add(ANDROID_REFERENCE_URL)