Test module metadata

burst-gradle-plugin/build.gradle.kts

@@ -16,9 +16,11 @@ dependencies {
   implementation(projects.burst)
   implementation(projects.burstKotlinPlugin)
   implementation(libs.kotlin.gradlePlugin)
+  testImplementation(kotlin("compiler-embeddable"))
   testImplementation(libs.assertk)
   testImplementation(libs.junit)
   testImplementation(libs.kotlin.test)
+  testImplementation(libs.kotlinx.metadata.klib)
 }
 
 buildConfig {

burst-gradle-plugin/src/test/kotlin/app/cash/burst/gradle/BurstGradlePluginTest.kt

@@ -52,12 +52,14 @@ class BurstGradlePluginTest {
     multiplatform(
       testTaskName = "${platformName}Test",
       platformName = platformName,
+      checkKlibMetadata = true,
     )
   }
 
   private fun multiplatform(
     testTaskName: String,
     platformName: String,
+    checkKlibMetadata: Boolean = false,
   ) {
     val projectDir = File("src/test/projects/multiplatform")
 
@@ -81,6 +83,20 @@ class BurstGradlePluginTest {
       val sampleSpecialization = testCases.single { it.name == "test_Milk[$platformName]" }
       assertThat(sampleSpecialization.skipped).isFalse()
     }
+
+    if (checkKlibMetadata) {
+      val klib = readKlib(
+        projectDir.resolve("lib/build/classes/kotlin/$platformName/test/klib/lib_test"),
+      )
+      val klibMetadata = klib.moduleMetadata()
+      val coffeeTestMetadata = klibMetadata.classes.first { it.name == "CoffeeTest" }
+      // TODO: This expected output is wrong. It should have specializations like test_Milk etc.
+      //     https://github.com/cashapp/burst/issues/87
+      assertThat(coffeeTestMetadata.functions.map { it.name }).containsExactlyInAnyOrder(
+        "setUp",
+        "test",
+      )
+    }
   }
 
   @Test

burst-gradle-plugin/src/test/kotlin/app/cash/burst/gradle/klib.kt

@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2025 Cash App
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package app.cash.burst.gradle
+
+import java.io.File
+import kotlin.metadata.KmClass
+import kotlinx.metadata.klib.KlibModuleFragmentReadStrategy
+import kotlinx.metadata.klib.KlibModuleMetadata
+import kotlinx.metadata.klib.KlibModuleMetadata.MetadataLibraryProvider
+import org.jetbrains.kotlin.konan.file.File as KonanFile
+import org.jetbrains.kotlin.library.KotlinLibrary
+import org.jetbrains.kotlin.library.ToolingSingleFileKlibResolveStrategy
+import org.jetbrains.kotlin.util.DummyLogger
+
+/**
+ * Decode a `.klib` file using APIs from the embeddable compiler.
+ */
+fun readKlib(klib: File): KotlinLibrary =
+  ToolingSingleFileKlibResolveStrategy.resolve(KonanFile(klib.toPath()), DummyLogger)
+
+/**
+ * Decode the metadata from a library.
+ */
+fun KotlinLibrary.moduleMetadata() = KlibModuleMetadata.read(
+  asMetadataLibraryProvider(),
+  KlibModuleFragmentReadStrategy.DEFAULT,
+)
+
+val KlibModuleMetadata.classes: Sequence<KmClass>
+  get() = fragments.asSequence().flatMap { it.classes }
+
+private fun KotlinLibrary.asMetadataLibraryProvider(): MetadataLibraryProvider {
+  val original = this
+  return object : MetadataLibraryProvider {
+    override val moduleHeaderData: ByteArray
+      get() = original.moduleHeaderData
+
+    override fun packageMetadata(fqName: String, partName: String) =
+      original.packageMetadata(fqName, partName)
+
+    override fun packageMetadataParts(fqName: String): Set<String> =
+      original.packageMetadataParts(fqName)
+  }
+}

gradle/libs.versions.toml

@@ -14,6 +14,7 @@ junit-vintage-engine = { module = "org.junit.vintage:junit-vintage-engine", vers
 kotlin-compile-testing = { module = "dev.zacsweers.kctfork:core", version = "0.7.0" }
 kotlin-gradlePlugin = { module = "org.jetbrains.kotlin:kotlin-gradle-plugin", version.ref = "kotlin" }
 kotlin-test = { module = "org.jetbrains.kotlin:kotlin-test" }
+kotlinx-metadata-klib = { module = "org.jetbrains.kotlinx:kotlinx-metadata-klib", version = "0.0.6" }
 mavenPublish-gradle-plugin = { module = "com.vanniktech:gradle-maven-publish-plugin", version = "0.30.0" }
 
 [plugins]