Support 'ExternalStaticDebugProbes' (in collaboration with the kotlin-stdlib)

Author: sellmair

Diff for: integration-testing/README.md

@@ -9,6 +9,7 @@ The tests are the following:
 * `debugAgentTest` checks that the coroutine debugger can be run as a Java agent.
 * `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)
+* `externalStaticDebugProbesTest` checks that a `ExternalStaticDebugProbes` is picked up by the kotlin stdlib
 * `smokeTest` builds the multiplatform test project that depends on coroutines.
 
 The `integration-testing` project is expected to be in a subdirectory of the main `kotlinx.coroutines` project.

Diff for: integration-testing/jpmsTest/build.gradle.kts

@@ -21,6 +21,7 @@ kotlin {
     jvmToolchain(17)
 
     val test = target.compilations.getByName("test")
+
     target.compilations.create("debugDynamicAgentJpmsTest") {
         associateWith(test)
 
@@ -35,6 +36,22 @@ kotlin {
             classpath = javaSourceSet.runtimeClasspath
         }
     }
+
+
+    target.compilations.create("externalStaticDebugProbesTest") {
+        associateWith(test)
+
+
+        defaultSourceSet.dependencies {
+            implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:$coroutines_version")
+            implementation("org.jetbrains.kotlinx:kotlinx-coroutines-debug:$coroutines_version")
+        }
+
+        tasks.register<Test>("externalStaticDebugProbesTest") {
+            testClassesDirs = output.classesDirs
+            classpath = javaSourceSet.runtimeClasspath
+        }
+    }
 }
 
 tasks.named("check") {

Diff for: integration-testing/jpmsTest/src/externalStaticDebugProbesTest/kotlin/ExternalStaticDebugProbes.kt

@@ -0,0 +1,10 @@
+package kotlinx.coroutines.external
+
+import kotlinx.coroutines.debug.internal.AbstractStaticDebugProbes
+import kotlin.coroutines.*
+
+object ExternalStaticDebugProbes: AbstractStaticDebugProbes() {
+    override fun <T> probeCoroutineCreated(completion: Continuation<T>): Continuation<T> {
+        return super.probeCoroutineCreated(completion)
+    }
+}

Diff for: integration-testing/jpmsTest/src/externalStaticDebugProbesTest/kotlin/ExternalStaticDebugProbesTest.kt

@@ -0,0 +1,20 @@
+import org.junit.*
+import kotlinx.coroutines.*
+import kotlinx.coroutines.external.ExternalStaticDebugProbes
+import org.junit.Test
+import java.io.*
+
+class ExternalStaticDebugProbesTest {
+
+    @Test
+    fun testDumpCoroutines() {
+        runBlocking {
+            val baos = ByteArrayOutputStream()
+            ExternalStaticDebugProbes.dumpCoroutines(PrintStream(baos))
+            // if the agent works, then dumps should contain something,
+            // at least the fact that this test is running.
+            val dump = baos.toString()
+            Assert.assertTrue(dump, dump.contains("testDumpCoroutines"))
+        }
+    }
+}

Diff for: kotlinx-coroutines-core/api/kotlinx-coroutines-core.api

@@ -911,6 +911,14 @@ public final class kotlinx/coroutines/channels/TickerMode : java/lang/Enum {
 	public static fun values ()[Lkotlinx/coroutines/channels/TickerMode;
 }
 
+public abstract class kotlinx/coroutines/debug/internal/AbstractStaticDebugProbes {
+	public fun <init> ()V
+	public final fun dumpCoroutines (Ljava/io/PrintStream;)V
+	public fun probeCoroutineCreated (Lkotlin/coroutines/Continuation;)Lkotlin/coroutines/Continuation;
+	public fun probeCoroutineResumed (Lkotlin/coroutines/Continuation;)V
+	public fun probeCoroutineSuspended (Lkotlin/coroutines/Continuation;)V
+}
+
 public final class kotlinx/coroutines/debug/internal/AgentInstallationType {
 	public static final field INSTANCE Lkotlinx/coroutines/debug/internal/AgentInstallationType;
 }

Diff for: kotlinx-coroutines-core/jvm/src/debug/internal/AbstractStaticDebugProbes.kt

@@ -0,0 +1,59 @@
+package kotlinx.coroutines.debug.internal
+
+import kotlinx.coroutines.*
+import java.io.*
+import kotlin.coroutines.*
+
+/**
+ * Allows to statically install 'Debug Probes' at the known location
+ * (kotlinx.coroutines.external.ExternalStaticDebugProbes).
+ *
+ * **Discussion**
+ *
+ * There are three methods of installing/engaging coroutines 'Debug Probes'
+ *
+ * 1) Dynamic Attach (using the 'kotlinx-coroutines-debug' module)
+ *  This uses runtime byte-code alteration to replace the 'Debug Probes' straight from the kotlin-stdlib
+ *
+ * 2) Static Attach using an Agent
+ *  This uses a java agent to replace the 'Debug Probes' from the kotlin-stdlib statically
+ *
+ * 3) ExternalStaticDebugProbes
+ *  The kotlin-stdlib compiled against a class at
+ *  `kotlinx.coroutines.external.ExternalStaticDebugProbes` which is not available at runtime, by default.
+ *  If a class at this location is present, then the kotlin-stdlib will call into it.
+ *
+ *  ```kotlin
+ *  package kotlinx.coroutines.external
+ *  object ExternalStaticDebugProbes: AbstractStaticDebugProbes() {
+ *      override fun <T> probeCoroutineCreated(completion: Continuation<T>): Continuation<T> {
+ *          // intercept
+ *          // ...
+ *
+ *          // forward to debugger machinery
+ *          return super.probeCoroutineCreated(completion)
+ *      }
+ *  }
+ *  ```
+ */
+@Suppress("unused")
+@DelicateCoroutinesApi
+@ExperimentalCoroutinesApi
+abstract class AbstractStaticDebugProbes {
+    init {
+        require(javaClass.name == "kotlinx.coroutines.external.ExternalStaticDebugProbes")
+        AgentInstallationType.isInstalledStatically = true
+        DebugProbesImpl.install()
+    }
+
+    open fun probeCoroutineResumed(frame: Continuation<*>) = DebugProbesImpl.probeCoroutineResumed(frame)
+
+    open fun probeCoroutineSuspended(frame: Continuation<*>) = DebugProbesImpl.probeCoroutineSuspended(frame)
+
+    open fun <T> probeCoroutineCreated(completion: Continuation<T>): Continuation<T> =
+        DebugProbesImpl.probeCoroutineCreated(completion)
+
+    fun dumpCoroutines(out: PrintStream) {
+        DebugProbesImpl.dumpCoroutines(out)
+    }
+}