Revert "Removed legacy onFinishing handler support from JobSupport"

This reverts commit b209e9b

Author: elizarov

common/kotlinx-coroutines-core-common/src/Builders.common.kt

@@ -210,9 +210,17 @@ private open class StandaloneCoroutine(
     private val parentContext: CoroutineContext,
     active: Boolean
 ) : AbstractCoroutine<Unit>(parentContext, active) {
+    override fun hasOnFinishingHandler(update: Any?) = update is CompletedExceptionally
+
     override fun handleJobException(exception: Throwable) {
         handleCoroutineException(parentContext, exception, this)
     }
+
+    override fun onFinishingInternal(update: Any?) {
+        if (update is CompletedExceptionally && update.cause !is CancellationException) {
+            parentContext[Job]?.cancel(update.cause)
+        }
+    }
 }
 
 private class LazyStandaloneCoroutine(

common/kotlinx-coroutines-core-common/src/JobSupport.kt

@@ -640,6 +640,7 @@ internal open class JobSupport constructor(active: Boolean) : Job, SelectClause0
     private fun tryMakeCancelling(expect: Incomplete, list: NodeList, cause: Throwable?): Boolean {
         val cancelled = Cancelled(this, cause)
         if (!_state.compareAndSet(expect, Finishing(list, cancelled, false))) return false
+        onFinishingInternal(cancelled)
         onCancellationInternal(cancelled)
         // Materialize cause
         notifyCancellation(list, cancelled.cause)
@@ -678,10 +679,10 @@ internal open class JobSupport constructor(active: Boolean) : Job, SelectClause0
             if (state is Finishing && state.completing)
                 return COMPLETING_ALREADY_COMPLETING
             val child: ChildJob? = firstChild(state) ?: // or else complete immediately w/o children
-            if (tryFinalizeState(state, proposedUpdate, mode)) {
-                return COMPLETING_COMPLETED
-            } else {
-                return@loopOnState // retry
+            when {
+                state !is Finishing && hasOnFinishingHandler(proposedUpdate) -> null // unless it has onFinishing handler
+                tryFinalizeState(state, proposedUpdate, mode) -> return COMPLETING_COMPLETED
+                else -> return@loopOnState
             }
             val list = state.list ?: // must promote to list to correctly operate on child lists
             when (state) {
@@ -703,6 +704,7 @@ internal open class JobSupport constructor(active: Boolean) : Job, SelectClause0
             val completing = Finishing(list, cancelled, true)
             if (_state.compareAndSet(state, completing)) {
                 (state as? Finishing)?.transferExceptions(completing)
+                if (state !is Finishing) onFinishingInternal(proposedUpdate)
                 if (child != null && tryWaitForChild(child, proposedUpdate))
                     return COMPLETING_WAITING_CHILDREN
                 if (tryFinalizeState(completing, proposedUpdate, mode = MODE_ATOMIC_DEFAULT))
@@ -798,6 +800,17 @@ internal open class JobSupport constructor(active: Boolean) : Job, SelectClause0
         // TODO rename to "onCancelling"
     }
 
+    /**
+     * Whether job has [onFinishingInternal] handler for given [update]
+     * @suppress **This is unstable API and it is subject to change.**
+     */
+    internal open fun hasOnFinishingHandler(update: Any?) = false
+
+    /**
+     * @suppress **This is unstable API and it is subject to change.**
+     */
+    internal open fun onFinishingInternal(update: Any?) {}
+
     /**
      * Method which is invoked once Job becomes [Cancelled] or [CompletedExceptionally].
      * It's guaranteed that at the moment of invocation the job and all its children are complete.