Gradle plugin: feed stubs to typedpythonStubs

docs/SPEC.md

@@ -274,6 +274,11 @@ All in `PM/commonTest`, so they run wherever the interpreter loads.
   README naming the Compose version and the commit, and `kotlin-stubs.zip` on every `v*` tag's release.
   `Status: partial` — the workflow could not be run where it was written; its YAML parses and its
   assemble step was executed locally.
+- **B-9** When a configuration named `typedpythonStubs` exists (toolchain's plugin creates it), every
+  stubs task's output directory is added to it, with the task dependency travelling with the files, in
+  either plugin application order. Without that configuration nothing happens and none is created.
+  `Status: implemented` — `GP/TypedPythonStubsWiringTest.kt` (a `ProjectBuilder` project; the toolchain
+  side that consumes the configuration is toolchain#23 and is not exercised here).
 
 ## 7. Threading and builds
 

python-multiplatform-gradle-plugin/src/main/kotlin/python/multiplatform/gradle/PythonBindingsPlugin.kt

@@ -21,6 +21,9 @@ private const val OPTION_EXCLUDE_PACKAGES = "python.multiplatform.excludePackage
 private const val ROLE_LIBRARY = "library"
 private const val ROLE_APP = "app"
 
+/** Created by toolchain's plugin (toolchain#23); referenced by name only. */
+private const val TYPEDPYTHON_STUBS_CONFIGURATION = "typedpythonStubs"
+
 /**
  * Which KSP configurations the processor belongs on.
  *
@@ -495,6 +498,20 @@ class PythonBindingsPlugin : Plugin<Project> {
             outputDirectory.set(project.layout.buildDirectory.dir("generated/pythonStubs/$sourceSetName"))
         }
         project.tasks.matching { it.name == "prepareKotlinIdeaImport" }.configureEach { dependsOn(task) }
+        feedTypedPythonStubs(project, task)
+    }
+
+    /**
+     * Adds [task]'s output to toolchain's `typedpythonStubs` configuration, by name only -- there is
+     * no compile-time dependency on toolchain. `matching` + `configureEach` covers a configuration
+     * that already exists and one created later, so plugin application order does not matter; if it
+     * never appears, nothing happens. The provider is `flatMap`ped from the task, so resolving the
+     * configuration runs the task.
+     */
+    private fun feedTypedPythonStubs(project: Project, task: org.gradle.api.tasks.TaskProvider<PythonStubsTask>) {
+        project.configurations.matching { it.name == TYPEDPYTHON_STUBS_CONFIGURATION }.configureEach {
+            project.dependencies.add(name, project.files(task.flatMap { it.outputDirectory }))
+        }
     }
 
     /**

python-multiplatform-gradle-plugin/src/test/kotlin/python/multiplatform/gradle/TypedPythonStubsWiringTest.kt

@@ -0,0 +1,82 @@
+package python.multiplatform.gradle
+
+import org.gradle.api.Project
+import org.gradle.testfixtures.ProjectBuilder
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+/**
+ * SPEC B-9 (python-multiplatform#27): the stubs task output reaches toolchain's `typedpythonStubs`
+ * configuration by name, with the task dependency attached, whichever side appears first.
+ */
+class TypedPythonStubsWiringTest {
+
+    private val configurationName = "typedpythonStubs"
+
+    private fun projectWith(sourceSets: List<String>): Project {
+        val project = ProjectBuilder.builder().build()
+        val container = project.container(DummySourceSet::class.java) { name -> DummySourceSet(name, project) }
+        sourceSets.forEach { container.create(it) }
+        project.extensions.add("kotlin", DummyKotlinExt(container))
+        sourceSets.forEach { project.configurations.create("${it}Classpath") }
+        return project
+    }
+
+    private fun wire(project: Project, sourceSets: List<String>) {
+        val extension = project.extensions.create("pythonBindingsUnderTest", PythonBindingsExtension::class.java)
+        extension.artifactIncludePackages.set(listOf("junit.runner"))
+        extension.artifactTargets.set(sourceSets.associate { "${it}Classpath" to it })
+        PythonBindingsPlugin().configureArtifactBindings(project, extension)
+    }
+
+    private fun stubsDir(project: Project, sourceSet: String) =
+        project.layout.buildDirectory.dir("generated/pythonStubs/$sourceSet").get().asFile
+
+    @Test
+    fun aConfigurationThatExistsBeforeTheWiringReceivesEverySourceSetsStubs() {
+        val sets = listOf("desktopMain", "androidNativeArm64Main")
+        val project = projectWith(sets)
+        project.configurations.create(configurationName)
+        wire(project, sets)
+
+        val files = project.configurations.getByName(configurationName).files
+        sets.forEach { assertTrue(stubsDir(project, it) in files, "$it missing from $files") }
+    }
+
+    @Test
+    fun aConfigurationCreatedAfterTheWiringReceivesTheStubsToo() {
+        val sets = listOf("desktopMain", "androidNativeArm64Main")
+        val project = projectWith(sets)
+        wire(project, sets)
+        project.configurations.create(configurationName)
+
+        val files = project.configurations.getByName(configurationName).files
+        sets.forEach { assertTrue(stubsDir(project, it) in files, "$it missing from $files") }
+    }
+
+    @Test
+    fun resolvingTheConfigurationDependsOnTheStubsTask() {
+        val project = projectWith(listOf("desktopMain"))
+        val configuration = project.configurations.create(configurationName)
+        wire(project, listOf("desktopMain"))
+
+        val deps = configuration.buildDependencies.getDependencies(null)
+        val names = deps.map { it.name }
+        assertTrue(
+            names.any { it.startsWith("generatePythonStubs") },
+            "the task must travel with the files; dependencies were $names",
+        )
+    }
+
+    @Test
+    fun withoutTheConfigurationNothingIsCreatedAndNothingFails() {
+        val project = projectWith(listOf("desktopMain"))
+        wire(project, listOf("desktopMain"))
+
+        assertNull(project.configurations.findByName(configurationName))
+        assertFalse(project.tasks.names.isEmpty())
+    }
+}