Avoid using Java9+ APIs in JUnit5 CoroutineTimeout (#4279)

Fixes #4278

integration-testing/README.md

@@ -10,6 +10,7 @@ The tests are the following:
 * `debugDynamicAgentTest` checks that `kotlinx-coroutines-debug` agent can self-attach dynamically to JVM as a standalone dependency.
 * `debugDynamicAgentJpmsTest` checks that `kotlinx-coroutines-debug` agent can self-attach dynamically to JVM as a standalone dependency  (with JPMS)
 * `smokeTest` builds the multiplatform test project that depends on coroutines.
+* `java8Test` checks that some APIs built with Java 9+ can be used with Java 8.
 
 The `integration-testing` project is expected to be in a subdirectory of the main `kotlinx.coroutines` project.
 

integration-testing/build.gradle

@@ -167,7 +167,7 @@ compileTestKotlin {
 }
 
 check {
-    dependsOn([jvmCoreTest, debugDynamicAgentTest, mavenTest, debugAgentTest, coreAgentTest, ":jpmsTest:check", 'smokeTest:build'])
+    dependsOn([jvmCoreTest, debugDynamicAgentTest, mavenTest, debugAgentTest, coreAgentTest, ":jpmsTest:check", 'smokeTest:build', "java8Test:check"])
 }
 compileKotlin {
     kotlinOptions {

integration-testing/gradle.properties

@@ -1,6 +1,7 @@
 kotlin_version=2.0.0
 coroutines_version=1.9.0-SNAPSHOT
 asm_version=9.3
+junit5_version=5.7.0
 
 kotlin.code.style=official
 kotlin.mpp.stability.nowarn=true

integration-testing/java8Test/build.gradle.kts

@@ -0,0 +1,25 @@
+plugins {
+    kotlin("jvm")
+}
+
+repositories {
+    mavenCentral()
+    maven("https://maven.pkg.jetbrains.space/kotlin/p/kotlin/dev")
+    // Coroutines from the outer project are published by previous CI buils step
+    mavenLocal()
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+
+val coroutinesVersion = property("coroutines_version")
+val junit5Version = property("junit5_version")
+
+kotlin {
+    jvmToolchain(8)
+    dependencies {
+        implementation("org.jetbrains.kotlinx:kotlinx-coroutines-debug:$coroutinesVersion")
+        testImplementation("org.junit.jupiter:junit-jupiter-engine:$junit5Version")
+    }
+}

integration-testing/java8Test/src/test/kotlin/JUnit5TimeoutCompilation.kt

@@ -0,0 +1,9 @@
+import kotlinx.coroutines.debug.junit5.CoroutinesTimeout
+import org.junit.jupiter.api.*
+
+class JUnit5TimeoutCompilation {
+    @CoroutinesTimeout(1000)
+    @Test
+    fun testCoroutinesTimeoutNotFailing() {
+    }
+}

integration-testing/settings.gradle

@@ -8,6 +8,7 @@ pluginManagement {
 }
 
 include 'smokeTest'
+include 'java8Test'
 include(":jpmsTest")
 
 rootProject.name = "kotlinx-coroutines-integration-testing"

integration-testing/smokeTest/build.gradle

@@ -76,4 +76,4 @@ rootProject.extensions.findByType(org.jetbrains.kotlin.gradle.targets.js.nodejs.
     // canary nodejs that supports recent Wasm GC changes
     it.nodeVersion = "21.0.0-v8-canary202309167e82ab1fa2"
     it.nodeDownloadBaseUrl = "https://nodejs.org/download/v8-canary"
-}
+}

kotlinx-coroutines-debug/src/junit/junit5/CoroutinesTimeoutExtension.kt

@@ -206,8 +206,12 @@ internal class CoroutinesTimeoutExtension internal constructor(
     }
 
     private fun<T> Class<T>.coroutinesTimeoutAnnotation(): Optional<CoroutinesTimeout> =
-        AnnotationSupport.findAnnotation(this, CoroutinesTimeout::class.java).or {
-            enclosingClass?.coroutinesTimeoutAnnotation() ?: Optional.empty()
+        AnnotationSupport.findAnnotation(this, CoroutinesTimeout::class.java).let {
+            when {
+                it.isPresent -> it
+                enclosingClass != null -> enclosingClass.coroutinesTimeoutAnnotation()
+                else -> Optional.empty()
+            }
         }
 
     private fun <T: Any?> interceptMethod(
@@ -232,7 +236,7 @@ internal class CoroutinesTimeoutExtension internal constructor(
         }
         /* The extension was registered via an annotation; check that we succeeded in finding the annotation that led to
         the extension being registered and taking its parameters. */
-        if (testAnnotationOptional.isEmpty && classAnnotationOptional.isEmpty) {
+        if (!testAnnotationOptional.isPresent && !classAnnotationOptional.isPresent) {
             throw UnsupportedOperationException("Timeout was registered with a CoroutinesTimeout annotation, but we were unable to find it. Please report this.")
         }
         return when {