Resolve dependencies as graph, support multiple modules in a project

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/HierarchicalMppIT.kt

@@ -427,8 +427,7 @@ class HierarchicalMppIT : BaseGradleIT() {
         shouldInclude: Iterable<Pair<String, String>> = emptyList(),
         shouldNotInclude: Iterable<Pair<String, String>> = emptyList()
     ) {
-        val taskOutput = getOutputForTask(taskPath.removePrefix(":"))
-        val compilerArgsLine = taskOutput.lines().single { "Kotlin compiler args:" in it }
+        val compilerArgsLine = output.lines().single { "$taskPath Kotlin compiler args:" in it }
         val classpathItems = compilerArgsLine.substringAfter("-classpath").substringBefore(" -").split(File.pathSeparator)
 
         val actualClasspath = classpathItems.joinToString("\n")

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/GradleProjectModuleBuilder.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.gradle.plugin.mpp
 import org.gradle.api.Named
 import org.gradle.api.Project
 import org.gradle.api.artifacts.Dependency
+import org.gradle.api.artifacts.ModuleDependency
 import org.gradle.api.artifacts.ProjectDependency
 import org.gradle.api.attributes.Attribute
 import org.gradle.api.attributes.AttributeContainer
@@ -16,44 +17,53 @@ import org.jetbrains.kotlin.gradle.dsl.KotlinSingleTargetExtension
 import org.jetbrains.kotlin.gradle.dsl.kotlinExtension
 import org.jetbrains.kotlin.gradle.dsl.multiplatformExtensionOrNull
 import org.jetbrains.kotlin.gradle.plugin.KotlinCompilation
-import org.jetbrains.kotlin.gradle.plugin.mpp.pm20.currentBuildId
-import org.jetbrains.kotlin.gradle.plugin.mpp.pm20.matchesModule
-import org.jetbrains.kotlin.gradle.plugin.mpp.pm20.representsProject
+import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
+import org.jetbrains.kotlin.gradle.plugin.KotlinTarget
+import org.jetbrains.kotlin.gradle.plugin.mpp.pm20.*
+import org.jetbrains.kotlin.gradle.plugin.sources.KotlinDependencyScope
 import org.jetbrains.kotlin.gradle.plugin.sources.getVisibleSourceSetsFromAssociateCompilations
 import org.jetbrains.kotlin.project.model.*
 
 class ProjectStructureMetadataModuleBuilder {
-    private val modulesCache = mutableMapOf<ModuleIdentifier, KotlinModule>()
+    private val modulesCache = mutableMapOf<KotlinModuleIdentifier, KotlinModule>()
 
     private fun buildModuleFromProjectStructureMetadata(
-        moduleIdentifier: ModuleIdentifier,
+        moduleIdentifier: KotlinModuleIdentifier,
         metadata: KotlinProjectStructureMetadata
     ): KotlinModule =
         BasicKotlinModule(moduleIdentifier).apply {
             metadata.sourceSetNamesByVariantName.keys.forEach { variantName ->
                 fragments.add(BasicKotlinModuleVariant(this@apply, variantName))
             }
+            fun fragment(sourceSetName: String): BasicKotlinModuleFragment {
+                if (fragments.none { it.fragmentName == sourceSetName })
+                    fragments.add(BasicKotlinModuleFragment(this@apply, sourceSetName))
+                return fragmentByName(sourceSetName)
+            }
             metadata.sourceSetNamesByVariantName.forEach { (variantName, sourceSets) ->
                 val variant = fragmentByName(variantName)
                 sourceSets.forEach { sourceSetName ->
-                    if (fragments.none { it.fragmentName == sourceSetName })
-                        fragments.add(BasicKotlinModuleFragment(this@apply, sourceSetName))
-                    val fragment = fragmentByName(sourceSetName)
-                    variant.directRefinesDependencies.add(fragment)
+                    variant.directRefinesDependencies.add(fragment(sourceSetName))
                 }
             }
-            metadata.sourceSetsDependsOnRelation.forEach { (depending, dependencies) ->
-                val dependingFragment = fragmentByName(depending)
+            metadata.sourceSetModuleDependencies.forEach { (sourceSetName, dependencies) ->
+                val fragment = fragment(sourceSetName)
                 dependencies.forEach { dependency ->
-                    if (fragments.none { it.fragmentName == dependency })
-                        fragments.add(BasicKotlinModuleFragment(this@apply, dependency))
-                    val fragment = fragmentByName(dependency)
-                    dependingFragment.directRefinesDependencies.add(fragment)
+                    fragment.declaredModuleDependencies.add(
+                        KotlinModuleDependency(MavenModuleIdentifier(dependency.groupId.orEmpty(), dependency.moduleId, null /* TODO */))
+                    )
+                }
+            }
+
+            metadata.sourceSetsDependsOnRelation.forEach { (depending, dependencies) ->
+                val dependingFragment = fragment(depending)
+                dependencies.forEach { dependency ->
+                    dependingFragment.directRefinesDependencies.add(fragment(dependency))
                 }
             }
         }
 
-    fun getModule(moduleIdentifier: ModuleIdentifier, projectStructureMetadata: KotlinProjectStructureMetadata): KotlinModule {
+    fun getModule(moduleIdentifier: KotlinModuleIdentifier, projectStructureMetadata: KotlinProjectStructureMetadata): KotlinModule {
         return modulesCache.getOrPut(moduleIdentifier) {
             buildModuleFromProjectStructureMetadata(
                 moduleIdentifier,
@@ -63,34 +73,81 @@ class ProjectStructureMetadataModuleBuilder {
     }
 }
 
+private fun detectModules(targets: Iterable<KotlinTarget>, sourceSets: Iterable<KotlinSourceSet>): Map<String, List<KotlinCompilation<*>>> {
+    // DSU-like approach: all compilations and source sets that are reachable via dependsOn edges are considered a single module
+
+    val compilations = targets.flatMap { it.compilations }
+
+    val dsu = mutableMapOf<Any, Any>().apply {
+        compilations.forEach { put(it, it) }
+        sourceSets.forEach { put(it, it) }
+    }
+
+    fun get(item: Any): Any =
+        dsu.getValue(item).let { leader -> if (leader === item) leader else get(leader).also { dsu[item] = it } }
+
+    fun union(item: Any, other: Any) = dsu.put(get(item), get(other))
+
+    sourceSets.forEach { sourceSet ->
+        sourceSet.dependsOn.forEach { other -> union(sourceSet, other) }
+    }
+    compilations.forEach { compilation ->
+        compilation.kotlinSourceSets.forEach { union(compilation, it) }
+    }
+    val uniqueCompilationNamesCounter = mutableMapOf<Set<String>, Int>()
+
+    fun moduleName(compilations: Iterable<KotlinCompilation<*>>): String {
+        val names = compilations.map { it.name }.toSortedSet()
+        val uniqueNumber = uniqueCompilationNamesCounter.put(names, uniqueCompilationNamesCounter[names]?.plus(1) ?: 0)
+        return names.joinToString("-") + (uniqueNumber?.let { "-$it" } ?: "")
+    }
+
+    return compilations.groupBy { get(it) }.values.associateBy { moduleName(it) }
+}
+
 @Suppress("unused")
 class GradleProjectModuleBuilder(private val addInferredSourceSetVisibilityAsExplicit: Boolean) {
-    fun buildModuleFromProject(project: Project): KotlinModule? {
+    fun buildModulesFromProject(project: Project): List<KotlinModule> {
         val extension = project.multiplatformExtensionOrNull
             ?: project.kotlinExtension
-            ?: return null
+            ?: return emptyList()
 
         val targets = when (extension) {
-            is KotlinMultiplatformExtension -> extension.targets.filter { it.name != "metadata" }
+            is KotlinMultiplatformExtension -> extension.targets.filter { it.name != KotlinMultiplatformPlugin.METADATA_TARGET_NAME }
             is KotlinSingleTargetExtension -> listOf(extension.target)
-            else -> return null
+            else -> return emptyList()
         }
 
-        return BasicKotlinModule(LocalModuleIdentifier(project.currentBuildId().name, project.path)).apply {
-            val variantToCompilation = mutableMapOf<KotlinModuleFragment, KotlinCompilation<*>>()
+        val moduleCompilationCluster = detectModules(targets, extension.sourceSets)
 
-            targets.forEach { target ->
-                val publishedVariantsByCompilation = (target as? AbstractKotlinTarget)?.kotlinComponents.orEmpty()
-                    .flatMap { component -> (component as? KotlinVariant)?.usages.orEmpty() }
-                    .groupBy { it.compilation }
+        val publishedVariantsByCompilation = targets.flatMap { target ->
+            (target as? AbstractKotlinTarget)?.kotlinComponents.orEmpty()
+                .flatMap { component -> (component as? KotlinVariant)?.usages.orEmpty() }
+        }.groupBy { it.compilation }
 
-                target.compilations.forEach { compilation ->
-                    val names =
-                        publishedVariantsByCompilation[compilation].orEmpty()
-                            .filter { it.includeIntoProjectStructureMetadata }.map { it.name }
+        val moduleByFragment = mutableMapOf<KotlinModuleFragment, KotlinModule>()
 
-                    names.forEach { variantName ->
+        val result = moduleCompilationCluster.entries.map { (classifier, compilationsToInclude) ->
+            val sourceSetsToInclude = compilationsToInclude.flatMapTo(mutableSetOf()) { it.allKotlinSourceSets }
+
+            val moduleIdentifier = LocalModuleIdentifier(
+                project.currentBuildId().name,
+                project.path,
+                classifier.takeIf { it != KotlinCompilation.MAIN_COMPILATION_NAME }
+            )
+
+            BasicKotlinModule(moduleIdentifier).apply {
+                val variantToCompilation = mutableMapOf<BasicKotlinModuleFragment, KotlinCompilation<*>>()
+
+                compilationsToInclude.forEach { compilation ->
+                    // A compilation may be exposed as more than one variant, so we collect all of its names
+                    val variantNames =
+                        publishedVariantsByCompilation[compilation]?.filter { it.includeIntoProjectStructureMetadata }?.map { it.name }
+                            ?: listOf(compilation.defaultSourceSetName)
+
+                    variantNames.forEach { variantName ->
                         val variant = BasicKotlinModuleVariant(this@apply, variantName)
+                        moduleByFragment[variant] = this@apply
                         variantToCompilation[variant] = compilation
                         fragments.add(variant)
 
@@ -104,50 +161,53 @@ class GradleProjectModuleBuilder(private val addInferredSourceSetVisibilityAsExp
                         variant.isExported = compilation.isMain()
                     }
                 }
-            }
-            extension.sourceSets.forEach { sourceSet ->
-                val existingVariant = fragments.filterIsInstance<BasicKotlinModuleVariant>().find { it.fragmentName == sourceSet.name }
-                val fragment = existingVariant ?: BasicKotlinModuleFragment(this@apply, sourceSet.name).also { fragments.add(it) }
-                fragment.kotlinSourceRoots = sourceSet.kotlin.sourceDirectories.toList()
+                // Once all fragments are created, add dependencies between them
+                sourceSetsToInclude.forEach { sourceSet ->
+                    val existingVariant = fragments.filterIsInstance<BasicKotlinModuleVariant>().find { it.fragmentName == sourceSet.name }
+                    val fragment = existingVariant ?: BasicKotlinModuleFragment(this@apply, sourceSet.name).also { fragments.add(it) }
+                    moduleByFragment[fragment] = this@apply
+                    fragment.kotlinSourceRoots = sourceSet.kotlin.sourceDirectories.toList()
 
-                // FIXME: Kotlin/Native implementation-effective-api dependencies are missing here. Introduce dependency scopes
-                project.configurations.getByName(sourceSet.apiConfigurationName).allDependencies.forEach {
-                    val moduleDependency = it.toModuleDependency(project)
-                    fragment.declaredModuleDependencies.add(moduleDependency)
-                }
-            }
-
-            // Once all fragments are created, add dependencies between them
-
-            fragments.forEach { fragment ->
-                val sourceSet = extension.sourceSets.findByName(fragment.fragmentName)
-                    ?: variantToCompilation.getValue(fragment).defaultSourceSet
-                sourceSet.dependsOn.forEach { dependency ->
-                    val dependencyFragment = fragmentByName(dependency.name)
-                    fragment.directRefinesDependencies.add(dependencyFragment)
-                }
-            }
-            targets.forEach { target ->
-                target.compilations.forEach { compilation ->
-                    val fragment = fragmentByName(compilation.defaultSourceSetName)
-                    compilation.associateWith.forEach { associate ->
-                        val dependencyFragment = fragmentByName(associate.defaultSourceSetName)
-                        fragment.declaredContainingModuleFragmentDependencies.add(dependencyFragment)
+                    // FIXME: Kotlin/Native implementation-effective-api dependencies are missing here. Introduce dependency scopes
+                    requestedDependencies(project, sourceSet, listOf(KotlinDependencyScope.API_SCOPE)).forEach {
+                        val moduleDependency = it.toModuleDependency(project)
+                        fragment.declaredModuleDependencies.add(moduleDependency)
                     }
                 }
-            }
-            if (addInferredSourceSetVisibilityAsExplicit) {
-                extension.sourceSets.forEach { sourceSet ->
-                    val fragment = fragmentByName(sourceSet.name)
-                    getVisibleSourceSetsFromAssociateCompilations(project, sourceSet).forEach { dependency ->
+                fragments.forEach { fragment ->
+                    val sourceSet = extension.sourceSets.findByName(fragment.fragmentName)
+                        ?: variantToCompilation.getValue(fragment).defaultSourceSet
+                    sourceSet.dependsOn.forEach { dependency ->
                         val dependencyFragment = fragmentByName(dependency.name)
-                        fragment.declaredContainingModuleFragmentDependencies.add(dependencyFragment)
+                        fragment.directRefinesDependencies.add(dependencyFragment)
                     }
                 }
             }
         }
-    }
 
+        fun fragmentByName(name: String) =
+            result.asSequence().flatMap { it.fragments.asSequence() }.first { it.fragmentName == name }
+
+        targets.flatMap { it.compilations }.forEach { compilation ->
+            val variant = fragmentByName(compilation.defaultSourceSetName)
+            compilation.associateWith.forEach { associate ->
+                val associateVariant = fragmentByName(associate.defaultSourceSetName)
+                variant.declaredModuleDependencies.add(KotlinModuleDependency(associateVariant.containingModule.moduleIdentifier))
+            }
+        }
+
+        if (addInferredSourceSetVisibilityAsExplicit) {
+            project.kotlinExtension.sourceSets.forEach { sourceSet ->
+                val fragment = fragmentByName(sourceSet.name)
+                getVisibleSourceSetsFromAssociateCompilations(project, sourceSet).forEach { dependency ->
+                    val dependencyFragment = fragmentByName(dependency.name)
+                    fragment.declaredModuleDependencies.add(KotlinModuleDependency(dependencyFragment.containingModule.moduleIdentifier))
+                }
+            }
+        }
+
+        return result
+    }
 
     private fun <T : Any> attributeString(container: AttributeContainer, attributeKey: Attribute<T>): String {
         val value = container.getAttribute(attributeKey)
@@ -158,13 +218,35 @@ class GradleProjectModuleBuilder(private val addInferredSourceSetVisibilityAsExp
     }
 }
 
+
+private fun <T : Any> attributeString(container: AttributeContainer, attributeKey: Attribute<T>): String {
+    val value = container.getAttribute(attributeKey)
+    return when (value) {
+        is Named -> value.name
+        else -> value.toString()
+    }
+}
+
 internal fun Dependency.toModuleDependency(
     project: Project
-) = when (val dependency = this) {
-    is ProjectDependency ->
-        ModuleDependency(LocalModuleIdentifier(project.currentBuildId().name, dependency.dependencyProject.path))
-    else ->
-        ModuleDependency(MavenModuleIdentifier(dependency.group.orEmpty(), dependency.name))
+): KotlinModuleDependency {
+    return KotlinModuleDependency(
+        when (this) {
+            is ProjectDependency ->
+                LocalModuleIdentifier(
+                    project.currentBuildId().name,
+                    dependencyProject.path,
+                    moduleClassifiersFromCapabilities(requestedCapabilities).single() // FIXME multiple capabilities
+                )
+            is ModuleDependency ->
+                MavenModuleIdentifier(
+                    group.orEmpty(),
+                    name,
+                    moduleClassifiersFromCapabilities(requestedCapabilities).single() // FIXME multiple capabilities
+                )
+            else -> MavenModuleIdentifier(group.orEmpty(), name, null)
+        }
+    )
 }
 
 private fun BasicKotlinModule.fragmentByName(name: String) =
@@ -194,7 +276,10 @@ class GradleModuleVariantResolver(val project: Project) : ModuleVariantResolver
                 .flatMap { it.usages }
                 .firstOrNull { it.name == requestingVariant.fragmentName }
                 ?.compilation
-                ?: return VariantResolution.NotRequested(requestingVariant, dependencyModule)
+                ?: targets.asSequence().flatMap { it.compilations.asSequence() }.single {
+                    it.defaultSourceSetName == requestingVariant.fragmentName
+                } // TODO: generalize the mapping PM2.0 <-> MPP
+                ?: return VariantResolution.Unknown(requestingVariant, dependencyModule)
 
         val compileClasspath = project.configurations.getByName(compilation.compileDependencyConfigurationName)
 

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/GranularMetadataTransformation.kt

@@ -18,6 +18,8 @@ import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 import org.jetbrains.kotlin.gradle.plugin.sources.KotlinDependencyScope
 import org.jetbrains.kotlin.gradle.plugin.sources.sourceSetDependencyConfigurationByScope
 import org.jetbrains.kotlin.gradle.targets.metadata.ALL_COMPILE_METADATA_CONFIGURATION_NAME
+import org.jetbrains.kotlin.gradle.targets.metadata.ALL_RUNTIME_METADATA_CONFIGURATION_NAME
+import org.jetbrains.kotlin.gradle.targets.metadata.dependsOnClosureWithInterCompilationDependencies
 import java.io.File
 import java.io.InputStream
 import java.util.*
@@ -85,7 +87,6 @@ internal class GranularMetadataTransformation(
     /** A list of scopes that the dependencies from [kotlinSourceSet] are treated as requested dependencies. */
     private val sourceSetRequestedScopes: List<KotlinDependencyScope>,
     /** A configuration that holds the dependencies of the appropriate scope for all Kotlin source sets in the project */
-    private val allSourceSetsConfiguration: Configuration,
     private val parentTransformations: Lazy<Iterable<GranularMetadataTransformation>>
 ) {
     val metadataDependencyResolutions: Iterable<MetadataDependencyResolution> by lazy { doTransform() }
@@ -98,40 +99,14 @@ internal class GranularMetadataTransformation(
     )
 
     private val requestedDependencies: Iterable<Dependency> by lazy {
-        fun collectScopedDependenciesFromSourceSet(sourceSet: KotlinSourceSet): Set<Dependency> =
-            sourceSetRequestedScopes.flatMapTo(mutableSetOf()) { scope ->
-                project.sourceSetDependencyConfigurationByScope(sourceSet, scope).incoming.dependencies
-            }
-
-        val ownDependencies = collectScopedDependenciesFromSourceSet(kotlinSourceSet)
-        val parentDependencies = parentTransformations.value.flatMapTo(mutableSetOf<Dependency>()) { it.requestedDependencies }
-
-        ownDependencies + parentDependencies
+        requestedDependencies(project, kotlinSourceSet, sourceSetRequestedScopes)
     }
 
+    private val allSourceSetsConfiguration: Configuration =
+        commonMetadataDependenciesConfigurationForScopes(project, sourceSetRequestedScopes)
+
     private val configurationToResolve: Configuration by lazy {
-        /** If [kotlinSourceSet] is not a published source set, its dependencies are not included in [allSourceSetsConfiguration].
-         * In that case, to resolve the dependencies of the source set in a way that is consistent with the published source sets,
-         * we need to create a new configuration with the dependencies from both [allSourceSetsConfiguration] and the
-         * input configuration(s) of the source set. */
-        var modifiedConfiguration: Configuration? = null
-
-        val originalDependencies = allSourceSetsConfiguration.allDependencies
-
-        requestedDependencies.forEach { dependency ->
-            if (dependency !in originalDependencies) {
-                modifiedConfiguration = modifiedConfiguration ?: project.configurations.detachedConfiguration().apply {
-                    fun <T> copyAttribute(key: Attribute<T>) {
-                        attributes.attribute(key, allSourceSetsConfiguration.attributes.getAttribute(key)!!)
-                    }
-                    allSourceSetsConfiguration.attributes.keySet().forEach { copyAttribute(it) }
-                    allSourceSetsConfiguration.extendsFrom.forEach { extendsFrom(it) }
-                }
-                modifiedConfiguration!!.dependencies.add(dependency)
-            }
-        }
-
-        modifiedConfiguration ?: allSourceSetsConfiguration
+        resolvableMetadataConfiguration(project, allSourceSetsConfiguration, requestedDependencies)
     }
 
     private fun doTransform(): Iterable<MetadataDependencyResolution> {
@@ -229,7 +204,7 @@ internal class GranularMetadataTransformation(
             project,
             module,
             configurationToResolve,
-            resolveViaAvailableAt = false // we will process this dependency later in the queue
+            resolveViaAvailableAt = false // we will process the available-at module as a dependency later in the queue
         )
 
         val resolvedToProject: Project? = (mppDependencyMetadataExtractor as? ProjectMppDependencyMetadataExtractor)?.dependencyProject
@@ -301,6 +276,75 @@ internal class GranularMetadataTransformation(
     }
 }
 
+internal fun resolvableMetadataConfiguration(
+    project: Project,
+    sourceSets: Iterable<KotlinSourceSet>,
+    scopes: Iterable<KotlinDependencyScope>
+) = resolvableMetadataConfiguration(
+    project,
+    commonMetadataDependenciesConfigurationForScopes(project, scopes),
+    sourceSets.flatMapTo(mutableListOf()) { requestedDependencies(project, it, scopes) }
+)
+
+/** If a source set is not a published source set, its dependencies are not included in [allSourceSetsConfiguration].
+ * In that case, to resolve the dependencies of the source set in a way that is consistent with the published source sets,
+ * we need to create a new configuration with the dependencies from both [allSourceSetsConfiguration] and the
+ * other [requestedDependencies] */
+// TODO: optimize by caching the resulting configurations?
+internal fun resolvableMetadataConfiguration(
+    project: Project,
+    allSourceSetsConfiguration: Configuration,
+    requestedDependencies: Iterable<Dependency>
+): Configuration {
+    var modifiedConfiguration: Configuration? = null
+
+    val originalDependencies = allSourceSetsConfiguration.allDependencies
+
+    requestedDependencies.forEach { dependency ->
+        if (dependency !in originalDependencies) {
+            modifiedConfiguration = modifiedConfiguration ?: project.configurations.detachedConfiguration().apply {
+                fun <T> copyAttribute(key: Attribute<T>) {
+                    attributes.attribute(key, allSourceSetsConfiguration.attributes.getAttribute(key)!!)
+                }
+                allSourceSetsConfiguration.attributes.keySet().forEach { copyAttribute(it) }
+                allSourceSetsConfiguration.extendsFrom.forEach { extendsFrom(it) }
+                dependencies.addAll(originalDependencies) // TODO: check if this line is redundant
+            }
+            modifiedConfiguration!!.dependencies.add(dependency)
+        }
+    }
+    return modifiedConfiguration ?: allSourceSetsConfiguration
+}
+
+/** The configuration that contains the dependencies of the corresponding scopes (and maybe others)
+ * from all published source sets. */
+internal fun commonMetadataDependenciesConfigurationForScopes(
+    project: Project,
+    scopes: Iterable<KotlinDependencyScope>
+): Configuration {
+    // TODO: what if 'runtimeOnly' is combined with 'compileOnly'? prohibit this or merge the two? we never do that now, though
+    val configurationName = if (KotlinDependencyScope.RUNTIME_ONLY_SCOPE in scopes)
+        ALL_RUNTIME_METADATA_CONFIGURATION_NAME
+    else
+        ALL_COMPILE_METADATA_CONFIGURATION_NAME
+    return project.configurations.getByName(configurationName)
+}
+
+internal fun requestedDependencies(
+    project: Project,
+    sourceSet: KotlinSourceSet,
+    requestedScopes: Iterable<KotlinDependencyScope>
+): Iterable<Dependency> {
+    fun collectScopedDependenciesFromSourceSet(sourceSet: KotlinSourceSet): Set<Dependency> =
+        requestedScopes.flatMapTo(mutableSetOf()) { scope ->
+            project.sourceSetDependencyConfigurationByScope(sourceSet, scope).incoming.dependencies
+        }
+
+    val otherContributingSourceSets = dependsOnClosureWithInterCompilationDependencies(project, sourceSet)
+    return listOf(sourceSet, *otherContributingSourceSets.toTypedArray()).flatMap(::collectScopedDependenciesFromSourceSet)
+}
+
+
 private abstract class MppDependencyMetadataExtractor(val project: Project, val dependency: ResolvedComponentResult) {
     abstract fun getProjectStructureMetadata(): KotlinProjectStructureMetadata?
 
@@ -343,7 +387,7 @@ private class IncludedBuildMetadataExtractor(
     init {
         val id = dependency.id
         require(id is ProjectComponentIdentifier) { "dependency should resolve to a project" }
-        require(!(id as ProjectComponentIdentifier).build.isCurrentBuild) { "should be a project from an included build" }
+        require(!id.build.isCurrentBuild) { "should be a project from an included build" }
         this.id = id
     }
 
@@ -493,7 +537,6 @@ internal fun getProjectStructureMetadata(
     module: ResolvedComponentResult,
     configuration: Configuration
 ): KotlinProjectStructureMetadata? {
-    // FIXME test dependencies won't work
     val extractor = getMetadataExtractor(project, module, configuration, resolveViaAvailableAt = true)
     return extractor?.getProjectStructureMetadata()
 }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/KotlinProjectStructureMetadata.kt

@@ -17,7 +17,9 @@ import org.jetbrains.kotlin.gradle.dsl.multiplatformExtensionOrNull
 import org.jetbrains.kotlin.gradle.plugin.sources.KotlinDependencyScope
 import org.jetbrains.kotlin.gradle.plugin.sources.withAllDependsOnSourceSets
 import org.jetbrains.kotlin.gradle.plugin.sources.sourceSetDependencyConfigurationByScope
+import org.jetbrains.kotlin.gradle.targets.metadata.dependsOnClosureWithInterCompilationDependencies
 import org.jetbrains.kotlin.gradle.targets.metadata.getPublishedPlatformCompilations
+import org.jetbrains.kotlin.gradle.targets.metadata.isSharedNativeSourceSet
 import org.w3c.dom.Document
 import org.w3c.dom.Element
 import org.w3c.dom.Node
@@ -114,14 +116,19 @@ internal fun buildKotlinProjectStructureMetadata(project: Project): KotlinProjec
              * published as API dependencies of the metadata module to get into the resolution result, see
              * [KotlinMetadataTargetConfigurator.exportDependenciesForPublishing].
              */
-            val isNativeSharedSourceSet = sourceSetsWithMetadataCompilations[sourceSet] is KotlinSharedNativeCompilation
-            val sourceSetExportedDependencies = when {
-                isNativeSharedSourceSet -> sourceSet.withAllDependsOnSourceSets().flatMap { hierarchySourceSet ->
-                    listOf(KotlinDependencyScope.API_SCOPE, KotlinDependencyScope.IMPLEMENTATION_SCOPE).flatMap { scope ->
-                        project.sourceSetDependencyConfigurationByScope(hierarchySourceSet, scope).allDependencies.toList()
-                    }
-                }.distinct()
-                else -> project.configurations.getByName(sourceSet.apiConfigurationName).allDependencies
+            val isNativeSharedSourceSet = isSharedNativeSourceSet(project, sourceSet)
+            val scopes = listOfNotNull(
+                KotlinDependencyScope.API_SCOPE,
+                KotlinDependencyScope.IMPLEMENTATION_SCOPE.takeIf { isNativeSharedSourceSet }
+            )
+            val sourceSetsToIncludeDependencies =
+                if (isNativeSharedSourceSet)
+                    dependsOnClosureWithInterCompilationDependencies(project, sourceSet).plus(sourceSet)
+                else listOf(sourceSet)
+            val sourceSetExportedDependencies = scopes.flatMap { scope ->
+                sourceSetsToIncludeDependencies.flatMap { hierarchySourceSet ->
+                    project.sourceSetDependencyConfigurationByScope(hierarchySourceSet, scope).allDependencies.toList()
+                }
             }
             sourceSet.name to sourceSetExportedDependencies.map { ModuleIds.fromDependency(it) }.toSet()
         },

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/TransformKotlinGranularMetadata.kt

@@ -15,6 +15,7 @@ import org.jetbrains.kotlin.gradle.plugin.sources.KotlinDependencyScope.*
 import org.jetbrains.kotlin.gradle.plugin.sources.withAllDependsOnSourceSets
 import org.jetbrains.kotlin.gradle.targets.metadata.ALL_COMPILE_METADATA_CONFIGURATION_NAME
 import org.jetbrains.kotlin.gradle.targets.metadata.KotlinMetadataTargetConfigurator
+import org.jetbrains.kotlin.gradle.targets.metadata.dependsOnClosureWithInterCompilationDependencies
 import org.jetbrains.kotlin.gradle.utils.getValue
 import java.io.File
 import javax.inject.Inject
@@ -77,9 +78,8 @@ open class TransformKotlinGranularMetadata
             project,
             kotlinSourceSet,
             listOf(API_SCOPE, IMPLEMENTATION_SCOPE, COMPILE_ONLY_SCOPE),
-            project.configurations.getByName(ALL_COMPILE_METADATA_CONFIGURATION_NAME),
             lazy {
-                KotlinMetadataTargetConfigurator.dependsOnWithInterCompilationDependencies(project, kotlinSourceSet).map {
+                dependsOnClosureWithInterCompilationDependencies(project, kotlinSourceSet).map {
                     project.tasks.withType(TransformKotlinGranularMetadata::class.java)
                         .getByName(KotlinMetadataTargetConfigurator.transformGranularMetadataTaskName(it.name))
                         .transformation
@@ -97,7 +97,7 @@ open class TransformKotlinGranularMetadata
     private val extractableFilesByResolution: Map<out MetadataDependencyResolution, ExtractableMetadataFiles>
         get() = metadataDependencyResolutions
             .filterIsInstance<MetadataDependencyResolution.ChooseVisibleSourceSets>()
-            .associate { it to it.getExtractableMetadataFiles(outputsDir) }
+            .associateWith { it.getExtractableMetadataFiles(outputsDir) }
 
     @get:Internal
     internal val filesByResolution: Map<out MetadataDependencyResolution, FileCollection>

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/kotlinCompilations.kt

@@ -338,6 +338,10 @@ internal object CompilationSourceSetUtil {
         return ext.get(EXT_NAME) as Property<CompilationsBySourceSet>
     }
 
+    // FIXME: the results include the compilations of the metadata target; the callers should care about filtering them out
+    //        if they need only the platform compilations
+    // TODO: create a separate util function: `platformCompilationsBySourceSets`
+    // TODO: visit all call sites, check if they handle the metadata compilations correctly
     fun compilationsBySourceSets(project: Project): CompilationsBySourceSet {
         val compilationNamesBySourceSetName = getOrCreateProperty(project) {
             var shouldFinalizeValue = false

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/pm20/DependencyGraphResolver.kt

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.gradle.plugin.mpp.pm20
+
+import org.gradle.api.Project
+import org.gradle.api.artifacts.Configuration
+import org.gradle.api.artifacts.result.ResolvedComponentResult
+import org.gradle.api.artifacts.result.ResolvedDependencyResult
+import org.jetbrains.kotlin.gradle.dsl.kotlinExtension
+import org.jetbrains.kotlin.gradle.plugin.mpp.resolvableMetadataConfiguration
+import org.jetbrains.kotlin.gradle.plugin.sources.KotlinDependencyScope
+import org.jetbrains.kotlin.project.model.*
+
+class GradleKotlinDependencyGraphResolver(
+    private val project: Project,
+    private val moduleResolver: ModuleDependencyResolver,
+    private val fragmentsResolver: ModuleFragmentsResolver
+) : KotlinDependencyGraphResolver {
+
+    private val configurationToResolve: Configuration
+        get() = resolvableMetadataConfiguration(
+            project,
+            project.kotlinExtension.sourceSets, // take dependencies from all source sets; TODO introduce consistency scopes?
+            KotlinDependencyScope.compileScopes
+        )
+
+    override fun resolveDependencyGraph(requestingModule: KotlinModule): DependencyGraphResolution {
+        if (!requestingModule.representsProject(project))
+            return DependencyGraphResolution.Unknown(requestingModule)
+
+        val excludeLegacyMetadataModulesFromResult = mutableSetOf<ResolvedComponentResult>()
+
+        val nodeByModuleId = mutableMapOf<KotlinModuleIdentifier, DependencyGraphNode>()
+
+        fun nodeFromComponent(component: ResolvedComponentResult, isRoot: Boolean /*refactor*/): DependencyGraphNode {
+            val id = component.toModuleIdentifier()
+            return nodeByModuleId.getOrPut(id) {
+                val module = if (isRoot)
+                    requestingModule
+                else moduleResolver.resolveDependency(component.toModuleDependency())
+                    .takeIf { component !in excludeLegacyMetadataModulesFromResult }
+                    ?: buildStubModule(component, component.variants.singleOrNull()?.displayName ?: "default")
+
+                val resolvedComponentDependencies = component.dependencies
+                    .filterIsInstance<ResolvedDependencyResult>()
+                    .flatMap { dependency -> dependency.requested.toModuleIdentifiers().map { id -> id to dependency.selected } }
+                    .toMap()
+
+                val fragmentDependencies = module.fragments.associateWith { it.declaredModuleDependencies }
+
+                val nodeDependenciesMap = fragmentDependencies.mapValues { (_, deps) ->
+                    deps.mapNotNull { resolvedComponentDependencies[it.moduleIdentifier] }.map { nodeFromComponent(it, isRoot = false) }
+                }
+
+                DependencyGraphNode(module, nodeDependenciesMap)
+            }
+        }
+
+        return DependencyGraphResolution.DependencyGraph(
+            requestingModule,
+            nodeFromComponent(configurationToResolve.incoming.resolutionResult.root, isRoot = true)
+        )
+    }
+}

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/pm20/DependencyResolution.kt

@@ -7,16 +7,17 @@ package org.jetbrains.kotlin.gradle.plugin.mpp.pm20
 
 import org.gradle.api.Project
 import org.gradle.api.artifacts.Configuration
-import org.gradle.api.artifacts.component.ComponentIdentifier
-import org.gradle.api.artifacts.component.ModuleComponentIdentifier
-import org.gradle.api.artifacts.component.ProjectComponentIdentifier
+import org.gradle.api.artifacts.component.*
 import org.gradle.api.artifacts.result.ResolvedComponentResult
 import org.gradle.api.artifacts.result.ResolvedDependencyResult
+import org.gradle.api.capabilities.Capability
 import org.jetbrains.kotlin.gradle.dsl.kotlinExtension
+import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 import org.jetbrains.kotlin.gradle.plugin.mpp.ProjectStructureMetadataModuleBuilder
 import org.jetbrains.kotlin.gradle.plugin.mpp.GradleProjectModuleBuilder
 import org.jetbrains.kotlin.gradle.plugin.mpp.getProjectStructureMetadata
-import org.jetbrains.kotlin.gradle.targets.metadata.ALL_COMPILE_METADATA_CONFIGURATION_NAME
+import org.jetbrains.kotlin.gradle.plugin.mpp.resolvableMetadataConfiguration
+import org.jetbrains.kotlin.gradle.plugin.sources.KotlinDependencyScope
 import org.jetbrains.kotlin.project.model.*
 import java.util.ArrayDeque
 
@@ -26,21 +27,29 @@ class GradleModuleDependencyResolver(
     private val projectModuleBuilder: GradleProjectModuleBuilder
 ) : ModuleDependencyResolver {
 
-    // FIXME this wont work for tests, as their dependencies are currently not in the all compile dependencies configuration
     private val configurationToResolve: Configuration
-        get() = project.configurations.getByName(ALL_COMPILE_METADATA_CONFIGURATION_NAME)
+        get() = resolvableMetadataConfiguration(
+            project,
+            project.kotlinExtension.sourceSets, // take dependencies from all source sets; TODO introduce consistency scopes?
+            listOf(KotlinDependencyScope.API_SCOPE, KotlinDependencyScope.IMPLEMENTATION_SCOPE, KotlinDependencyScope.COMPILE_ONLY_SCOPE)
+        )
 
-    override fun resolveDependency(moduleDependency: ModuleDependency): KotlinModule? {
+    override fun resolveDependency(moduleDependency: KotlinModuleDependency): KotlinModule? {
         val allComponents = configurationToResolve.incoming.resolutionResult.allComponents
-        // TODO: optimize O(n) search, store the resolved components with dependency keys
+        // TODO: optimize O(n) search, store the resolved components with dependency keys?
         val component = allComponents.find { it.id.matchesModuleDependency(moduleDependency) }
         val id = component?.id
+
+        //FIXME multiple?
+        val classifier = moduleClassifiersFromCapabilities(component?.variants?.flatMap { it.capabilities }.orEmpty()).single()
+
         return when {
             id is ProjectComponentIdentifier && id.build.isCurrentBuild ->
-                projectModuleBuilder.buildModuleFromProject(project.project(id.projectPath))
+                projectModuleBuilder.buildModulesFromProject(project.project(id.projectPath))
+                    .find { it.moduleIdentifier.moduleClassifier == classifier }
             id is ModuleComponentIdentifier -> {
                 val metadata = getProjectStructureMetadata(project, component, configurationToResolve) ?: return null
-                projectStructureMetadataModuleBuilder.getModule(id.toModuleIdentifier(), metadata)
+                projectStructureMetadataModuleBuilder.getModule(id.toModuleIdentifier(classifier), metadata)
             }
             else -> null
         }
@@ -52,7 +61,7 @@ class GradleProjectDependencyDiscovery(
     private val variantDependencyDiscovery: VariantDependencyDiscovery,
     private val fragmentDependenciesDiscovery: FragmentDependenciesDiscovery
 ) : DependencyDiscovery {
-    override fun discoverDependencies(fragment: KotlinModuleFragment): Iterable<ModuleDependency> {
+    override fun discoverDependencies(fragment: KotlinModuleFragment): Iterable<KotlinModuleDependency> {
         require(fragment.containingModule.representsProject(project))
         return when (fragment) {
             is KotlinModuleVariant -> variantDependencyDiscovery.discoverDependencies(fragment)
@@ -63,63 +72,88 @@ class GradleProjectDependencyDiscovery(
 
 class FragmentDependenciesDiscovery(
     private val project: Project,
-    private val expansion: InternalDependencyExpansion,
     private val moduleResolver: ModuleDependencyResolver,
-    private val fragmentsResolver: KotlinModuleFragmentsResolver
+    private val fragmentsResolver: ModuleFragmentsResolver
 ) : DependencyDiscovery {
-    override fun discoverDependencies(fragment: KotlinModuleFragment): Iterable<ModuleDependency> {
+    private val dependencyScopes = listOf(KotlinDependencyScope.API_SCOPE, KotlinDependencyScope.IMPLEMENTATION_SCOPE)
+
+    private fun KotlinModuleFragment.toSourceSet(): KotlinSourceSet = project.kotlinExtension.sourceSets.getByName(fragmentName)
+
+    // TODO: use the dependency graph resolution implementation?
+    override fun discoverDependencies(fragment: KotlinModuleFragment): Iterable<KotlinModuleDependency> {
         require(fragment.containingModule.representsProject(project))
 
-        val requested = expansion.expandInternalFragmentDependencies(fragment).visibleFragments().plus(fragment.refinesClosure)
-            .flatMap { it.declaredModuleDependencies }
-            .toSet()
+        val fragmentsWhoseDependenciesAreVisible = fragment.refinesClosure
 
-        // FIXME: test dependencies won't work here
-        val allComponents =
-            project.configurations.getByName(ALL_COMPILE_METADATA_CONFIGURATION_NAME).incoming.resolutionResult.allComponents
+        // FIXME use dependencyScopes, not just sets of declared module dependencies
+        val requestedDependencies = fragmentsWhoseDependenciesAreVisible.flatMap { it.declaredModuleDependencies }.toSet()
 
-        val componentByModuleDependency = allComponents.associateBy { it.toModuleDependency() }
+        val configurationToResolve = resolvableMetadataConfiguration(
+            project,
+            fragmentsWhoseDependenciesAreVisible.map { it.toSourceSet() },
+            KotlinDependencyScope.compileScopes
+        )
+        val allComponents = configurationToResolve.incoming.resolutionResult.allComponents
+
+        val componentsByRequestedDependency =
+            allComponents.flatMap { component -> component.dependents.map { it to component } }.toMap()
+                .mapKeys { it.key.requested.toModuleDependency() }
 
         val resolvedComponentQueue = ArrayDeque<ResolvedComponentResult>().apply {
-            addAll(componentByModuleDependency.filterKeys { it in requested }.values)
+            addAll(componentsByRequestedDependency.filterKeys { it in requestedDependencies }.values)
         }
 
         val visited = mutableSetOf<ResolvedComponentResult>()
+        val excludeLegacyMetadataModulesFromResult = mutableSetOf<ResolvedComponentResult>()
 
         while (resolvedComponentQueue.isNotEmpty()) {
             val component = resolvedComponentQueue.removeFirst()
             visited.add(component)
 
             val module = moduleResolver.resolveDependency(component.toModuleDependency())
+                .takeIf { component !in excludeLegacyMetadataModulesFromResult }
                 ?: buildStubModule(component, component.variants.singleOrNull()?.displayName ?: "default")
 
-            val newTransitiveDeps = when (val fragmentsResolution = fragmentsResolver.getChosenFragments(fragment, module)) {
+            val transitiveDepsToVisit = when (val fragmentsResolution = fragmentsResolver.getChosenFragments(fragment, module)) {
                 is FragmentResolution.ChosenFragments ->
                     fragmentsResolution.visibleFragments.flatMap { it.declaredModuleDependencies }.mapNotNull { dependency ->
-                        componentByModuleDependency[dependency].takeIf { component -> component !in visited }
+                        componentsByRequestedDependency[dependency]
                     }
                 else -> emptyList()
             }
 
+            val newTransitiveDeps = transitiveDepsToVisit.filterTo(mutableListOf()) { it !in visited }
+
+            // With legacy publication scheme, the root MPP module may have a single 'dependency' (available-at) to the metadata module
+            val isMetadataModulePublishedSeparately =
+                getProjectStructureMetadata(project, component, configurationToResolve)
+                    ?.let { !it.isPublishedAsRoot }
+                    ?: false
+            val singleDependencyComponentOrNull = (component.dependencies.singleOrNull() as? ResolvedDependencyResult)?.selected
+            if (isMetadataModulePublishedSeparately && singleDependencyComponentOrNull != null) {
+                newTransitiveDeps.add(singleDependencyComponentOrNull)
+                excludeLegacyMetadataModulesFromResult.add(singleDependencyComponentOrNull)
+            }
+
             resolvedComponentQueue.addAll(newTransitiveDeps)
         }
 
-        return visited.map { it.toModuleDependency() }
+        return (visited - excludeLegacyMetadataModulesFromResult).map { it.toModuleDependency() }
     }
+}
 
-    // refactor extract to a separate class
-    // TODO think about multi-variant stub modules for non-Kotlin modules which got more than one chosen variant
-    private fun buildStubModule(resolvedComponentResult: ResolvedComponentResult, singleVariantName: String): KotlinModule {
-        val moduleDependency = resolvedComponentResult.toModuleDependency()
-        return BasicKotlinModule(moduleDependency.moduleIdentifier).apply {
-            BasicKotlinModuleVariant(this@apply, singleVariantName).apply {
-                fragments.add(this)
-                this.declaredModuleDependencies.addAll(
-                    resolvedComponentResult.dependencies
-                        .filterIsInstance<ResolvedDependencyResult>()
-                        .map { it.selected.toModuleDependency() }
-                )
-            }
+// refactor extract to a separate class/interface
+// TODO think about multi-variant stub modules for non-Kotlin modules which got more than one chosen variant
+internal fun buildStubModule(resolvedComponentResult: ResolvedComponentResult, singleVariantName: String): KotlinModule {
+    val moduleDependency = resolvedComponentResult.toModuleDependency()
+    return BasicKotlinModule(moduleDependency.moduleIdentifier).apply {
+        BasicKotlinModuleVariant(this@apply, singleVariantName).apply {
+            fragments.add(this)
+            this.declaredModuleDependencies.addAll(
+                resolvedComponentResult.dependencies
+                    .filterIsInstance<ResolvedDependencyResult>()
+                    .map { it.selected.toModuleDependency() }
+            )
         }
     }
 }
@@ -142,24 +176,28 @@ class VariantDependencyDiscovery(
         return configuration.incoming.resolutionResult.allComponents
     }
 
-    override fun discoverDependencies(fragment: KotlinModuleFragment): Iterable<ModuleDependency> {
+    override fun discoverDependencies(fragment: KotlinModuleFragment): Iterable<KotlinModuleDependency> {
         require(fragment is KotlinModuleVariant)
         require(fragment.containingModule.representsProject(project))
 
         val components = resolvedComponentResults(fragment)
-        return components.mapNotNull { component ->
-            val moduleIdentifier = when (val id = component.id) {
-                is ProjectComponentIdentifier -> LocalModuleIdentifier(id.build.name, id.projectPath)
-                is ModuleComponentIdentifier -> id.toModuleIdentifier()
-                else -> return@mapNotNull null // TODO check that no other options are possible, throw errors?
+        return components.flatMap { component ->
+            val classifiers = moduleClassifiersFromCapabilities(component.variants.flatMap { it.capabilities })
+            when (val id = component.id) {
+                is ProjectComponentIdentifier -> {
+                    classifiers.map { LocalModuleIdentifier(id.build.name, id.projectPath, it) }
+                }
+                is ModuleComponentIdentifier -> {
+                    classifiers.map { id.toModuleIdentifier(it) }
+                }
+                else -> return@flatMap emptyList<KotlinModuleIdentifier>() // TODO check that no other options are possible, throw errors?
             }
-            ModuleDependency(moduleIdentifier)
-        }
+        }.map(::KotlinModuleDependency)
     }
 }
 
-private fun ModuleComponentIdentifier.toModuleIdentifier(): MavenModuleIdentifier =
-    MavenModuleIdentifier(moduleIdentifier.group, moduleIdentifier.name)
+private fun ModuleComponentIdentifier.toModuleIdentifier(classifier: String? = null): MavenModuleIdentifier =
+    MavenModuleIdentifier(moduleIdentifier.group, moduleIdentifier.name, classifier)
 
 internal fun ComponentIdentifier.matchesModule(module: KotlinModule): Boolean {
     return when (val moduleId = module.moduleIdentifier) {
@@ -175,15 +213,37 @@ internal fun ComponentIdentifier.matchesModule(module: KotlinModule): Boolean {
     }
 }
 
-internal fun ResolvedComponentResult.toModuleDependency(): ModuleDependency = ModuleDependency(
-    when (val id = id) {
-        is ProjectComponentIdentifier -> LocalModuleIdentifier(id.build.name, id.projectPath)
+internal fun ResolvedComponentResult.toModuleIdentifier(): KotlinModuleIdentifier {
+    val capabilities = variants.flatMap { it.capabilities } // expected to be disjoint
+    val moduleClassifier = moduleClassifiersFromCapabilities(capabilities).single() // FIXME handle multiple capabilities
+    return when (val id = id) {
+        is ProjectComponentIdentifier -> LocalModuleIdentifier(id.build.name, id.projectPath, moduleClassifier)
         is ModuleComponentIdentifier -> id.toModuleIdentifier()
-        else -> MavenModuleIdentifier(moduleVersion?.group.orEmpty(), moduleVersion?.name.orEmpty())
+        else -> MavenModuleIdentifier(moduleVersion?.group.orEmpty(), moduleVersion?.name.orEmpty(), moduleClassifier)
     }
-)
+}
 
-internal fun ComponentIdentifier.matchesModuleDependency(moduleDependency: ModuleDependency) =
+internal fun moduleClassifiersFromCapabilities(capabilities: Iterable<Capability>): Iterable<String?> {
+    val classifierCapabilities = capabilities.filter { it.name.contains("..") }
+    return if (classifierCapabilities.none()) listOf(null) else classifierCapabilities.map { it.name.substringAfterLast("..") /*FIXME invent a more stable scheme*/ }
+}
+
+internal fun ComponentSelector.toModuleIdentifiers(): Iterable<KotlinModuleIdentifier> {
+    val moduleClassifiers = moduleClassifiersFromCapabilities(requestedCapabilities)
+    return when (this) {
+        is ProjectComponentSelector -> moduleClassifiers.map { LocalModuleIdentifier(buildName, projectPath, it) }
+        is ModuleComponentSelector -> moduleClassifiers.map { MavenModuleIdentifier(moduleIdentifier.group, moduleIdentifier.name, it) }
+        else -> error("unexpected component selector")
+    }
+}
+
+internal fun ResolvedComponentResult.toModuleDependency(): KotlinModuleDependency = KotlinModuleDependency(toModuleIdentifier())
+internal fun ComponentSelector.toModuleDependency(): KotlinModuleDependency {
+    val moduleId = toModuleIdentifiers().single() // FIXME handle multiple
+    return KotlinModuleDependency(moduleId)
+}
+
+internal fun ComponentIdentifier.matchesModuleDependency(moduleDependency: KotlinModuleDependency) =
     when (val id = moduleDependency.moduleIdentifier) {
         is LocalModuleIdentifier -> {
             val projectId = this as? ProjectComponentIdentifier

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/sources/KotlinDependencyScope.kt

@@ -19,7 +19,11 @@ internal enum class KotlinDependencyScope(val scopeName: String) {
     API_SCOPE(API),
     IMPLEMENTATION_SCOPE(IMPLEMENTATION),
     COMPILE_ONLY_SCOPE(COMPILE_ONLY),
-    RUNTIME_ONLY_SCOPE(RUNTIME_ONLY)
+    RUNTIME_ONLY_SCOPE(RUNTIME_ONLY);
+
+    companion object {
+        val compileScopes = listOf(KotlinDependencyScope.API_SCOPE, KotlinDependencyScope.IMPLEMENTATION_SCOPE, KotlinDependencyScope.COMPILE_ONLY_SCOPE)
+    }
 }
 
 internal fun Project.sourceSetDependencyConfigurationByScope(sourceSet: KotlinSourceSet, scope: KotlinDependencyScope): Configuration =

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/metadata/KotlinMetadataTargetConfigurator.kt

@@ -18,6 +18,7 @@ import org.gradle.api.tasks.bundling.Zip
 import org.jetbrains.kotlin.gradle.dsl.KotlinCommonOptions
 import org.jetbrains.kotlin.gradle.dsl.kotlinExtension
 import org.jetbrains.kotlin.gradle.dsl.multiplatformExtension
+import org.jetbrains.kotlin.gradle.dsl.multiplatformExtensionOrNull
 import org.jetbrains.kotlin.gradle.plugin.*
 import org.jetbrains.kotlin.gradle.plugin.mpp.*
 import org.jetbrains.kotlin.gradle.plugin.mpp.CompilationSourceSetUtil.compilationsBySourceSets
@@ -53,11 +54,6 @@ class KotlinMetadataTargetConfigurator(kotlinPluginVersion: String) :
 
         internal fun transformGranularMetadataTaskName(sourceSetName: String) =
             lowerCamelCaseName("transform", sourceSetName, "DependenciesMetadata")
-
-        internal fun dependsOnWithInterCompilationDependencies(project: Project, sourceSet: KotlinSourceSet): Set<KotlinSourceSet> =
-            sourceSet.dependsOn.toMutableSet().apply {
-                addAll(getVisibleSourceSetsFromAssociateCompilations(project, sourceSet))
-            }
     }
 
     override fun configureTarget(target: KotlinMetadataTarget) {
@@ -292,11 +288,10 @@ class KotlinMetadataTargetConfigurator(kotlinPluginVersion: String) :
 
         val compilationName = sourceSet.name
 
-        val platformCompilations = compilationsBySourceSets(project).getValue(sourceSet)
+        val platformCompilations = compilationsBySourceSets(project)
+            .getValue(sourceSet).filter { it.target.name != KotlinMultiplatformPlugin.METADATA_TARGET_NAME }
 
-        val isNativeSourceSet = platformCompilations.all { compilation ->
-            compilation.target is KotlinNativeTarget || compilation is KotlinSharedNativeCompilation
-        }
+        val isNativeSourceSet = isSharedNativeSourceSet(project, sourceSet)
 
         val compilationFactory: KotlinCompilationFactory<out AbstractKotlinCompilation<*>> = when {
             isNativeSourceSet -> KotlinSharedNativeCompilationFactory(
@@ -362,20 +357,12 @@ class KotlinMetadataTargetConfigurator(kotlinPluginVersion: String) :
         isSourceSetPublished: Boolean
     ) {
         KotlinDependencyScope.values().forEach { scope ->
-            val allMetadataConfiguration = project.configurations.getByName(
-                when (scope) {
-                    KotlinDependencyScope.RUNTIME_ONLY_SCOPE -> ALL_RUNTIME_METADATA_CONFIGURATION_NAME
-                    else -> ALL_COMPILE_METADATA_CONFIGURATION_NAME
-                }
-            )
-
             val granularMetadataTransformation = GranularMetadataTransformation(
                 project,
                 sourceSet,
                 listOf(scope),
-                allMetadataConfiguration,
                 lazy {
-                    dependsOnWithInterCompilationDependencies(project, sourceSet).filterIsInstance<DefaultKotlinSourceSet>()
+                    dependsOnClosureWithInterCompilationDependencies(project, sourceSet).filterIsInstance<DefaultKotlinSourceSet>()
                         .map { checkNotNull(it.dependencyTransformations[scope]) }
                 }
             )
@@ -565,6 +552,20 @@ class KotlinMetadataTargetConfigurator(kotlinPluginVersion: String) :
         }
 }
 
+internal fun isSharedNativeSourceSet(project: Project, sourceSet: KotlinSourceSet): Boolean {
+    val compilations = CompilationSourceSetUtil.compilationsBySourceSets(project)[sourceSet].orEmpty()
+    return compilations.isNotEmpty() && compilations.all {
+        it.platformType == KotlinPlatformType.common || it.platformType == KotlinPlatformType.native
+    }
+}
+
+internal fun dependsOnClosureWithInterCompilationDependencies(project: Project, sourceSet: KotlinSourceSet): Set<KotlinSourceSet> =
+    sourceSet.getSourceSetHierarchy().toMutableSet().apply {
+        /** exclude self from the results of [getSourceSetHierarchy] */
+        remove(sourceSet)
+        addAll(getVisibleSourceSetsFromAssociateCompilations(project, sourceSet))
+    }
+
 /**
  * @return All common source sets that can potentially be published. Right now, not all combinations of platforms actually
  * support metadata compilation (see [KotlinMetadataTargetConfigurator.isMetadataCompilationSupported].

libraries/tools/kotlin-project-model/src/main/kotlin/DependencyResolution.kt

@@ -9,7 +9,7 @@ package org.jetbrains.kotlin.project.model
 // TODO think about state management: unresolved -> (known dependency graph?) ... -> completely resolved
 //      it seems to be important to learn whether or not the model is final
 interface ModuleDependencyResolver {
-    fun resolveDependency(moduleDependency: ModuleDependency): KotlinModule?
+    fun resolveDependency(moduleDependency: KotlinModuleDependency): KotlinModule?
 }
 
 // TODO merge with ModuleDependencyResolver?
@@ -17,5 +17,21 @@ interface ModuleDependencyResolver {
 interface DependencyDiscovery {
     // TODO return dependency graph rather than just iterable?
     // TODO make this a partial function, too
-    fun discoverDependencies(fragment: KotlinModuleFragment): Iterable<ModuleDependency>
-}
+    fun discoverDependencies(fragment: KotlinModuleFragment): Iterable<KotlinModuleDependency>
+}
+
+interface KotlinDependencyGraphResolver {
+    // TODO add explicit dependency consistency scopes if we decide to keep non-production code in the same variant
+    fun resolveDependencyGraph(requestingModule: KotlinModule): DependencyGraphResolution
+}
+
+sealed class DependencyGraphResolution(val requestingModule: KotlinModule) {
+    class Unknown(requestingModule: KotlinModule) : DependencyGraphResolution(requestingModule)
+    class DependencyGraph(requestingModule: KotlinModule, val root: DependencyGraphNode): DependencyGraphResolution(requestingModule)
+}
+
+// TODO: should this be a single graph for all dependency scopes as well, not just for all fragments?
+class DependencyGraphNode(
+    val module: KotlinModule,
+    val dependenciesByFragment: Map<KotlinModuleFragment, Iterable<DependencyGraphNode>>
+)

libraries/tools/kotlin-project-model/src/main/kotlin/InternalDependencyExpansion.kt

@@ -1,135 +0,0 @@
-/*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.project.model
-
-import org.jetbrains.kotlin.project.model.utils.variantsContainingFragment
-import java.util.ArrayDeque
-
-interface InternalDependencyExpansion {
-    fun expandInternalFragmentDependencies(consumingFragment: KotlinModuleFragment): InternalDependencyExpansionResult
-}
-
-class InternalDependencyExpansionResult(
-    val entries: Iterable<Entry>
-) {
-    sealed class ExpansionOutcome(val variantMatchingResults: Iterable<VariantResolution>) {
-        class VisibleFragments(
-            val fragments: Iterable<KotlinModuleFragment>,
-            variantMatchingResults: Iterable<VariantResolution>
-        ) : ExpansionOutcome(
-            variantMatchingResults
-        )
-
-        class Failure(variantMatchingResults: Iterable<VariantResolution>) : ExpansionOutcome(variantMatchingResults)
-    }
-
-    class Entry(
-        val dependingFragment: KotlinModuleFragment,
-        val dependencyFragment: KotlinModuleFragment,
-        val outcome: ExpansionOutcome
-    )
-}
-
-fun InternalDependencyExpansionResult.visibleFragments(): List<KotlinModuleFragment> =
-    entries.flatMap { entry -> entry.outcome.visibleFragments() }
-
-fun InternalDependencyExpansionResult.ExpansionOutcome.visibleFragments(): Iterable<KotlinModuleFragment> = when (this) {
-    is InternalDependencyExpansionResult.ExpansionOutcome.VisibleFragments -> fragments
-    else -> emptyList()
-}
-
-class DefaultInternalDependencyExpansion(
-    private val variantResolver: ContainingModuleVariantResolver
-) : InternalDependencyExpansion {
-    interface ContainingModuleVariantResolver {
-        fun getChosenVariant(
-            dependingVariant: KotlinModuleVariant,
-            candidateVariants: Iterable<KotlinModuleVariant>
-        ): VariantResolution
-    }
-
-    override fun expandInternalFragmentDependencies(consumingFragment: KotlinModuleFragment): InternalDependencyExpansionResult {
-        val visited = mutableSetOf(consumingFragment)
-        val answer = mutableListOf<InternalDependencyExpansionResult.Entry>()
-
-        /**
-         * For each fragment **t** that we consider a source of declared dependencies that we should expand for [consumingFragment]:
-         * - also consider the refines-closure of **t** as sources of declared dependencies
-         * - expand the declared dependencies of **t** to a set of fragments **F**
-         * - add the expansion result to the answer
-         * - also consider all fragments in **F** as sources of declared dependencies
-         */
-        val declaredDependencySourceQueue = ArrayDeque<KotlinModuleFragment>().apply { add(consumingFragment) }
-        while (declaredDependencySourceQueue.isNotEmpty()) {
-            val declaredDependencySource = declaredDependencySourceQueue.removeFirst()
-            declaredDependencySourceQueue.addAll(declaredDependencySource.refinesClosure.filter(visited::add))
-            val declaredDependenciesToExpand = declaredDependencySource.declaredContainingModuleFragmentDependencies
-            declaredDependenciesToExpand.forEach { declaredDependency ->
-                val answerEntry = expandSingleDeclaredDependency(consumingFragment, declaredDependencySource, declaredDependency)
-                answer += answerEntry
-                declaredDependencySourceQueue.addAll(answerEntry.outcome.visibleFragments())
-            }
-        }
-
-        return InternalDependencyExpansionResult(answer)
-    }
-
-    private fun expandSingleDeclaredDependency(
-        consumingFragment: KotlinModuleFragment,
-        declaredDependencySource: KotlinModuleFragment,
-        declaredDependency: KotlinModuleFragment
-    ): InternalDependencyExpansionResult.Entry {
-        /**
-         * Go over the variants containing the fragment that we infer the expansion for (note: it's the original consuming fragment, which
-         * may not necessarily be the same as the fragment holding the declared dependency if the latter comes from the closure).
-         *
-         * For each such containing variant v_i, let w_i be the variant containing the declared dependency fragment. Failure to choose
-         * prevents us from inferring the dependency expansion and is reported as a failure to expand the dependency.
-         *
-         * Then intersect the refined fragments of each w_i and use the intersection as the result.
-         */
-
-        val (consumingVariants, producingVariants) =
-            listOf(consumingFragment, declaredDependency).map { it.containingModule.variantsContainingFragment(it).toSet() }
-
-        val chosenVariants = consumingVariants.map { consumingVariant ->
-            if (consumingVariant in producingVariants)
-                VariantResolution.VariantMatch(consumingVariant, consumingVariant.containingModule, consumingVariant)
-            else
-                variantResolver.getChosenVariant(consumingVariant, producingVariants)
-        }
-
-        val mismatchedConsumingVariants = chosenVariants.filter { it !is VariantResolution.VariantMatch }
-
-        val outcome =
-            if (mismatchedConsumingVariants.isNotEmpty())
-                InternalDependencyExpansionResult.ExpansionOutcome.Failure(chosenVariants)
-            else
-                InternalDependencyExpansionResult.ExpansionOutcome.VisibleFragments(
-                    chosenVariants
-                        .map { (it as VariantResolution.VariantMatch).chosenVariant.refinesClosure }
-                        .reduce { acc, it -> acc.intersect(it) },
-                    chosenVariants
-                )
-
-        return InternalDependencyExpansionResult.Entry(declaredDependencySource, declaredDependency, outcome)
-    }
-}
-
-/**
- * This implementation matches the variants of the module by checking
- * their [KotlinModuleFragment.declaredContainingModuleFragmentDependencies], similar to how associate compilations work in MPP.
- * If more than one such dependency is declared, the result is deemed ambiguous.
- */
-class AssociateVariants : DefaultInternalDependencyExpansion.ContainingModuleVariantResolver {
-    override fun getChosenVariant(
-        dependingVariant: KotlinModuleVariant,
-        candidateVariants: Iterable<KotlinModuleVariant>
-    ): VariantResolution {
-        val result = candidateVariants.filter { it in dependingVariant.declaredContainingModuleFragmentDependencies }
-        return VariantResolution.fromMatchingVariants(dependingVariant, dependingVariant.containingModule, result)
-    }
-}

libraries/tools/kotlin-project-model/src/main/kotlin/KotlinModule.kt

@@ -6,34 +6,47 @@
 package org.jetbrains.kotlin.project.model
 
 // TODO sealed with an abstract subclass? this will make exhaustive checks work
-open class ModuleIdentifier
+open class KotlinModuleIdentifier(open val moduleClassifier: String?)
 
 // TODO consider id: Any, to allow IDs with custom equality?
-data class LocalModuleIdentifier(val buildId: String, val projectId: String) : ModuleIdentifier() {
+data class LocalModuleIdentifier(
+    val buildId: String,
+    val projectId: String,
+    override val moduleClassifier: String?
+) : KotlinModuleIdentifier(moduleClassifier) {
     companion object {
         private const val SINGLE_BUILD_ID = ":"
     }
 
-    override fun toString(): String = "project '$projectId'" + buildId.takeIf { it != SINGLE_BUILD_ID }?.let { "(build '$it')" }.orEmpty()
+    override fun toString(): String =
+        "project '$projectId'" +
+                moduleClassifier?.let { " / $it" }.orEmpty() +
+                buildId.takeIf { it != SINGLE_BUILD_ID }?.let { "(build '$it')" }.orEmpty()
 }
 
-data class MavenModuleIdentifier(val group: String, val name: String) : ModuleIdentifier() {
-    override fun toString(): String = "$group:$name"
+data class MavenModuleIdentifier(
+    val group: String,
+    val name: String,
+    override val moduleClassifier: String?
+) : KotlinModuleIdentifier(moduleClassifier) {
+    override fun toString(): String = "$group:$name" + moduleClassifier?.let { " / $it" }.orEmpty()
 }
 
 // TODO Gradle allows having multiple capabilities in a published module, we need to figure out how we can include them in the module IDs
 
 interface KotlinModule {
-    val moduleIdentifier: ModuleIdentifier
+    val moduleIdentifier: KotlinModuleIdentifier
 
     val fragments: Iterable<KotlinModuleFragment>
 
     val variants: Iterable<KotlinModuleVariant>
         get() = fragments.filterIsInstance<KotlinModuleVariant>()
+
+    // TODO: isSynthetic?
 }
 
 class BasicKotlinModule(
-    override val moduleIdentifier: ModuleIdentifier
+    override val moduleIdentifier: KotlinModuleIdentifier
 ) : KotlinModule {
     override val fragments = mutableListOf<BasicKotlinModuleFragment>()
 

libraries/tools/kotlin-project-model/src/main/kotlin/KotlinModuleDependency.kt

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.project.model
 
-data class ModuleDependency(val moduleIdentifier: ModuleIdentifier) {
+data class KotlinModuleDependency(val moduleIdentifier: KotlinModuleIdentifier) {
     override fun toString(): String = "dependency $moduleIdentifier"
 }
 

libraries/tools/kotlin-project-model/src/main/kotlin/KotlinModuleFragment.kt

@@ -14,10 +14,8 @@ interface KotlinModuleFragment {
     val fragmentName: String
     val directRefinesDependencies: Iterable<KotlinModuleFragment>
 
-    val declaredContainingModuleFragmentDependencies: Iterable<KotlinModuleFragment>
-
     // TODO: scopes
-    val declaredModuleDependencies: Iterable<ModuleDependency>
+    val declaredModuleDependencies: Iterable<KotlinModuleDependency>
 
     val kotlinSourceRoots: Iterable<File>
 }
@@ -54,8 +52,7 @@ open class BasicKotlinModuleFragment(
 
     override val directRefinesDependencies: MutableSet<BasicKotlinModuleFragment> = mutableSetOf()
 
-    override val declaredContainingModuleFragmentDependencies: MutableSet<BasicKotlinModuleFragment> = mutableSetOf()
-    override val declaredModuleDependencies: MutableSet<ModuleDependency> = mutableSetOf()
+    override val declaredModuleDependencies: MutableSet<KotlinModuleDependency> = mutableSetOf()
 
     override var kotlinSourceRoots: Iterable<File> = emptyList()
     override fun toString(): String = "fragment $fragmentName"

libraries/tools/kotlin-project-model/src/main/kotlin/ModuleFragmentsResolver.kt

@@ -7,7 +7,7 @@ package org.jetbrains.kotlin.project.model
 
 import org.jetbrains.kotlin.project.model.utils.variantsContainingFragment
 
-interface KotlinModuleFragmentsResolver {
+interface ModuleFragmentsResolver {
     fun getChosenFragments(
         requestingFragment: KotlinModuleFragment,
         dependencyModule: KotlinModule
@@ -30,18 +30,23 @@ sealed class FragmentResolution(val requestingFragment: KotlinModuleFragment, va
         FragmentResolution(requestingFragment, dependencyModule)
 }
 
-class DefaultKotlinModuleFragmentsResolver(
+class DefaultModuleFragmentsResolver(
     private val variantResolver: ModuleVariantResolver
-) : KotlinModuleFragmentsResolver {
+) : ModuleFragmentsResolver {
     override fun getChosenFragments(
         requestingFragment: KotlinModuleFragment,
         dependencyModule: KotlinModule
-    ): FragmentResolution.ChosenFragments {
+    ): FragmentResolution {
         val dependingModule = requestingFragment.containingModule
         val containingVariants = dependingModule.variantsContainingFragment(requestingFragment)
 
         val chosenVariants = containingVariants.map { variantResolver.getChosenVariant(it, dependencyModule) }
 
+        // TODO: extend this to more cases with non-matching variants, revisit the behavior when no matching variant is found once we fix
+        //       local publishing of libraries with missing host-specific parts (it breaks transitive dependencies now)
+        if (chosenVariants.none { it is VariantResolution.VariantMatch })
+            return FragmentResolution.NotRequested(requestingFragment, dependencyModule)
+
         val chosenFragments = chosenVariants.map { variantResolution ->
             when (variantResolution) {
                 is VariantResolution.VariantMatch -> variantResolution.chosenVariant.refinesClosure

libraries/tools/kotlin-project-model/src/test/kotlin/org/jetbrains/kotlin/project/model/DefaultModuleFragmentsResolverTest.kt

@@ -9,11 +9,11 @@ import org.junit.Assume.assumeTrue
 import org.junit.Test
 import kotlin.test.assertEquals
 
-class DefaultKotlinModuleFragmentsResolverTest {
+class DefaultModuleFragmentsResolverTest {
     val moduleFoo = simpleModule("foo")
     val moduleBar = simpleModule("bar")
 
-    val fragmentResolver = DefaultKotlinModuleFragmentsResolver(MatchVariantsByExactAttributes())
+    val fragmentResolver = DefaultModuleFragmentsResolver(MatchVariantsByExactAttributes())
 
     @Test
     fun testFragmentVisibility() {