Introduce CoroutineStackFrame and implement it in SuspendFunctionGun …

…reusable completion in order to properly walk through stackframes of interceptors

ktor-utils/ktor-utils-ios/src/io/ktor/util/StackFramesIos.kt

@@ -0,0 +1,10 @@
+package io.ktor.util
+
+@Suppress("UNUSED")
+internal actual interface CoroutineStackFrame {
+ public actual val callerFrame: CoroutineStackFrame?
+ public actual fun getStackTraceElement(): StackTraceElement?
+}
+
+@Suppress("ACTUAL_WITHOUT_EXPECT")
+actual typealias StackTraceElement = Any

ktor-utils/ktor-utils-js/src/io/ktor/util/StackFramesJs.kt

@@ -0,0 +1,10 @@
+package io.ktor.util
+
+@Suppress("UNUSED")
+internal actual interface CoroutineStackFrame {
+ public actual val callerFrame: CoroutineStackFrame?
+ public actual fun getStackTraceElement(): StackTraceElement?
+}
+
+@Suppress("ACTUAL_WITHOUT_EXPECT")
+actual typealias StackTraceElement = Any

ktor-utils/ktor-utils-jvm/src/io/ktor/util/StackFramesJvm.kt

@@ -0,0 +1,7 @@
+package io.ktor.util
+
+@Suppress("ACTUAL_WITHOUT_EXPECT")
+actual typealias CoroutineStackFrame = kotlin.coroutines.jvm.internal.CoroutineStackFrame
+
+@Suppress("ACTUAL_WITHOUT_EXPECT")
+actual typealias StackTraceElement = java.lang.StackTraceElement

ktor-utils/ktor-utils-jvm/test/io/ktor/tests/utils/PipelineStackFramesTest.kt

@@ -0,0 +1,69 @@
+package io.ktor.tests.utils
+
+import io.ktor.util.*
+import io.ktor.util.pipeline.*
+import kotlinx.coroutines.*
+import org.junit.Test
+import kotlin.coroutines.*
+import kotlin.coroutines.intrinsics.*
+import kotlin.test.*
+
+class PipelineStackFramesTest {
+ private val phase = PipelinePhase("StubPhase")
+ private lateinit var interceptorContinuation: Continuation<Unit>
+
+ @Test
+ fun testStackTraceWalking() {
+ val pipeline = Pipeline<Unit, Unit>(phase)
+ pipeline.intercept(phase) {
+ captureContinuation()
+ }
+
+ runBlocking {
+ runPipeline(pipeline)
+ }
+
+ val frame = interceptorContinuation as CoroutineStackFrame
+ val stacktrace = buildString {
+ var currentTop: CoroutineStackFrame? = frame
+ while (currentTop != null) {
+ val element = currentTop.getStackTraceElement()
+ if (element != null) {
+ append(element)
+ append('\n')
+ }
+ currentTop = currentTop.callerFrame
+ }
+ }
+
+ val filtered = stacktrace
+ .replace(Regex(":[0-9]+"), "") // line numbers
+ .replace(Regex("\n.*invokeSuspend.*\n"), "\n") // lambdas
+ assertEquals(filtered,
+ "io/ktor/tests/utils/PipelineStackFramesTest.nestedCapture(PipelineStackFramesTest.kt)\n" +
+ "io/ktor/tests/utils/PipelineStackFramesTest.captureContinuation(PipelineStackFramesTest.kt)\n" +
+ "io/ktor/tests/utils/PipelineStackFramesTest.runPipeline(PipelineStackFramesTest.kt)\n"
+ )
+ }
+
+ private suspend fun runPipeline(pipeline: Pipeline<Unit, Unit>) {
+ pipeline.execute(Unit, Unit)
+ preventTailCall()
+ }
+
+ private suspend fun captureContinuation() {
+ nestedCapture()
+ preventTailCall()
+ }
+
+ private suspend fun nestedCapture() {
+ suspendCoroutineUninterceptedOrReturn<Unit> {
+ interceptorContinuation = it
+ Unit
+ }
+ preventTailCall()
+ }
+
+ private fun preventTailCall() {
+ }
+}

ktor-utils/src/io/ktor/util/StackFrames.kt

@@ -0,0 +1,8 @@
+package io.ktor.util
+
+internal expect class StackTraceElement
+
+internal expect interface CoroutineStackFrame {
+ public val callerFrame: CoroutineStackFrame?
+ public fun getStackTraceElement(): StackTraceElement?
+}

ktor-utils/src/io/ktor/util/pipeline/PipelineContext.kt

@@ -70,7 +70,12 @@ private class SuspendFunctionGun<TSubject : Any, TContext : Any>(
 
  // this is impossible to inline because of property name clash
  // between PipelineContext.context and Continuation.context
- private val continuation: Continuation<Unit> = object : Continuation<Unit> {
+ private val continuation: Continuation<Unit> = object : Continuation<Unit>, CoroutineStackFrame {
+ override val callerFrame: CoroutineStackFrame?
+ get() = proceedContinuation as? CoroutineStackFrame
+
+ override fun getStackTraceElement(): StackTraceElement? = null
+
  @Suppress("UNCHECKED_CAST")
  override val context: CoroutineContext
  get () {
@@ -97,13 +102,16 @@ private class SuspendFunctionGun<TSubject : Any, TContext : Any>(
  private set
 
  private var rootContinuation: Any? = null
+ // Continuation where 'proceed' was called in order to properly walk over stacktrace
+ private var proceedContinuation: Continuation<*>? = null
  private var index = 0
 
  override fun finish() {
  index = blocks.size
  }
 
  override suspend fun proceed(): TSubject = suspendCoroutineUninterceptedOrReturn { continuation ->
+ proceedContinuation = continuation
  if (index == blocks.size) return@suspendCoroutineUninterceptedOrReturn subject
 
  addContinuation(continuation)