[Gradle] Handle multiplatform composite builds when metadata.jar is not yet present

KT-52172

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/CompositeMetadataArtifact.kt

@@ -21,6 +21,11 @@ internal interface CompositeMetadataArtifact {
      * Alternatively use the [read] function instead.
      */
     fun open(): CompositeMetadataArtifactContent
+
+    /**
+     * Checks if physical files are present on disk
+     */
+    fun exists(): Boolean
 }
 
 /**

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/CompositeMetadataArtifactImpl.kt

@@ -26,6 +26,10 @@ internal class CompositeMetadataArtifactImpl(
     private val hostSpecificArtifactFilesBySourceSetName: Map<String, File>
 ) : CompositeMetadataArtifact {
 
+    override fun exists(): Boolean {
+        return primaryArtifactFile.exists() && hostSpecificArtifactFilesBySourceSetName.values.all { it.exists() }
+    }
+
     override fun open(): CompositeMetadataArtifactContent {
         return CompositeMetadataArtifactContentImpl()
     }

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/MetadataDependencyTransformationTask.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.gradle.targets.metadata.ResolvedMetadataFilesProvide
 import org.jetbrains.kotlin.gradle.targets.metadata.dependsOnClosureWithInterCompilationDependencies
 import org.jetbrains.kotlin.gradle.utils.getValue
 import org.jetbrains.kotlin.gradle.utils.notCompatibleWithConfigurationCacheCompat
+import org.jetbrains.kotlin.gradle.utils.outputFilesProvider
 import java.io.File
 import javax.inject.Inject
 
@@ -117,8 +118,11 @@ open class MetadataDependencyTransformationTask
         get() = metadataDependencyResolutions
             .filterIsInstance<MetadataDependencyResolution.ChooseVisibleSourceSets>()
             .associateWith { chooseVisibleSourceSets ->
-                val files = project.transformMetadataLibrariesForBuild(chooseVisibleSourceSets, outputsDir, materializeFiles = false)
-                project.files(files).builtBy(this)
+                outputFilesProvider {
+                    project.transformMetadataLibrariesForBuild(
+                        chooseVisibleSourceSets, outputsDir, materializeFiles = false
+                    )
+                }
             }
 
     @TaskAction

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/transformMetadataLibraries.kt

@@ -82,6 +82,16 @@ private fun transformMetadataLibrariesForBuild(
     materializeFiles: Boolean,
     compositeMetadataArtifact: CompositeMetadataArtifact
 ): Set<File> {
+    /*
+    Careful handling of composite builds:
+    Right now, composite multiplatform builds will compile against the composite artifact build by the producer build (not
+    against compiled source sets directly).
+
+    This means, that this function might be called to figure out task inputs at a time, where
+    this composite artifact is not present on disk yet.
+     */
+    if (!materializeFiles && !compositeMetadataArtifact.exists()) return emptySet()
+
     return compositeMetadataArtifact.read { artifactContent ->
         resolution.visibleSourceSetNamesExcludingDependsOn.mapNotNull { visibleSourceSetName ->
             val sourceSetContent = artifactContent.findSourceSet(visibleSourceSetName) ?: return@mapNotNull null
@@ -94,4 +104,4 @@ private fun transformMetadataLibrariesForBuild(
             metadataLibraryFile
         }
     }.toSet()
-}
+}