Add Flow.onStart, support emit in onCompletion

* All "emitting" operators (onStart, transform, onCompletion) are moved
  to Emitter
* All transformations in Transform.kt are rewritten via (unsafe)
  transforms, but all of
  (safe) transform, onStart and onCompletion operators collectors
  are safe.
* Added migration for startWith and concatWith.
* Consistent docs for all migration functions.
* JvmMultifileClass for Migration.kt so that renamed/deprecated
  functions (when they moved there) continue to resolve.

Fixes #1168

Author: elizarov

binary-compatibility-validator/reference-public-api/kotlinx-coroutines-core.txt

@@ -801,6 +801,9 @@ public abstract interface class kotlinx/coroutines/flow/FlowCollector {
 
 public final class kotlinx/coroutines/flow/FlowKt {
 	public static final field DEFAULT_CONCURRENCY_PROPERTY_NAME Ljava/lang/String;
+	public static final fun BehaviourSubject ()Ljava/lang/Object;
+	public static final fun PublishSubject ()Ljava/lang/Object;
+	public static final fun ReplaySubject ()Ljava/lang/Object;
 	public static final fun asFlow (Ljava/lang/Iterable;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun asFlow (Ljava/util/Iterator;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun asFlow (Lkotlin/jvm/functions/Function0;)Lkotlinx/coroutines/flow/Flow;
@@ -827,6 +830,10 @@ public final class kotlinx/coroutines/flow/FlowKt {
 	public static final fun combineLatest (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function6;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun combineLatest (Lkotlinx/coroutines/flow/Flow;[Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function0;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
 	public static final synthetic fun combineLatest (Lkotlinx/coroutines/flow/Flow;[Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun compose (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun concatMap (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun concatWith (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun concatWith (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun conflate (Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun count (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public static final fun count (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
@@ -846,9 +853,11 @@ public final class kotlinx/coroutines/flow/FlowKt {
 	public static final fun filterNotNull (Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun first (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public static final fun first (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
+	public static final fun flatMap (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun flatMapConcat (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun flatMapMerge (Lkotlinx/coroutines/flow/Flow;ILkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
 	public static synthetic fun flatMapMerge$default (Lkotlinx/coroutines/flow/Flow;ILkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun flatten (Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun flattenConcat (Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun flattenMerge (Lkotlinx/coroutines/flow/Flow;I)Lkotlinx/coroutines/flow/Flow;
 	public static synthetic fun flattenMerge$default (Lkotlinx/coroutines/flow/Flow;IILjava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
@@ -861,15 +870,26 @@ public final class kotlinx/coroutines/flow/FlowKt {
 	public static final fun flowWith (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/CoroutineContext;ILkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/flow/Flow;
 	public static synthetic fun flowWith$default (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/CoroutineContext;ILkotlin/jvm/functions/Function1;ILjava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun fold (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;Lkotlin/jvm/functions/Function3;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
+	public static final fun forEach (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)V
 	public static final fun getDEFAULT_CONCURRENCY ()I
 	public static final fun launchIn (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/CoroutineScope;)Lkotlinx/coroutines/Job;
 	public static final fun map (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun mapNotNull (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun onCompletion (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun merge (Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun observeOn (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/CoroutineContext;)Lkotlinx/coroutines/flow/Flow;
+	public static final synthetic fun onCompletion (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun onCompletion (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function3;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun onEach (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun onErrorCollect (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/flow/Flow;
 	public static synthetic fun onErrorCollect$default (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun onErrorResume (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun onErrorResumeNext (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun onErrorReturn (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun onErrorReturn (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/flow/Flow;
+	public static synthetic fun onErrorReturn$default (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun onStart (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun produceIn (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/CoroutineScope;)Lkotlinx/coroutines/channels/ReceiveChannel;
+	public static final fun publishOn (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/CoroutineContext;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun reduce (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function3;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public static final synthetic fun retry (Lkotlinx/coroutines/flow/Flow;ILkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun retry (Lkotlinx/coroutines/flow/Flow;JLkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
@@ -878,9 +898,17 @@ public final class kotlinx/coroutines/flow/FlowKt {
 	public static final fun retryWhen (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function4;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun sample (Lkotlinx/coroutines/flow/Flow;J)Lkotlinx/coroutines/flow/Flow;
 	public static final fun scan (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;Lkotlin/jvm/functions/Function3;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun scanFold (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;Lkotlin/jvm/functions/Function3;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun scanReduce (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function3;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun single (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public static final fun singleOrNull (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
+	public static final fun skip (Lkotlinx/coroutines/flow/Flow;I)Lkotlinx/coroutines/flow/Flow;
+	public static final fun startWith (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun startWith (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun subscribe (Lkotlinx/coroutines/flow/Flow;)V
+	public static final fun subscribe (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)V
+	public static final fun subscribe (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;Lkotlin/jvm/functions/Function2;)V
+	public static final fun subscribeOn (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/CoroutineContext;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun switchMap (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun take (Lkotlinx/coroutines/flow/Flow;I)Lkotlinx/coroutines/flow/Flow;
 	public static final fun takeWhile (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
@@ -891,33 +919,9 @@ public final class kotlinx/coroutines/flow/FlowKt {
 	public static synthetic fun toSet$default (Lkotlinx/coroutines/flow/Flow;Ljava/util/Set;Lkotlin/coroutines/Continuation;ILjava/lang/Object;)Ljava/lang/Object;
 	public static final fun transform (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function3;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun unsafeFlow (Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun zip (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function3;)Lkotlinx/coroutines/flow/Flow;
-}
-
-public final class kotlinx/coroutines/flow/MigrationKt {
-	public static final fun BehaviourSubject ()Ljava/lang/Object;
-	public static final fun PublishSubject ()Ljava/lang/Object;
-	public static final fun ReplaySubject ()Ljava/lang/Object;
-	public static final fun compose (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun concatMap (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun flatMap (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun flatten (Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun forEach (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)V
-	public static final fun merge (Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun observeOn (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/CoroutineContext;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun onErrorResume (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun onErrorResumeNext (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun onErrorReturn (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun onErrorReturn (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/flow/Flow;
-	public static synthetic fun onErrorReturn$default (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun publishOn (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/CoroutineContext;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun scanFold (Lkotlinx/coroutines/flow/Flow;Ljava/lang/Object;Lkotlin/jvm/functions/Function3;)Lkotlinx/coroutines/flow/Flow;
-	public static final fun skip (Lkotlinx/coroutines/flow/Flow;I)Lkotlinx/coroutines/flow/Flow;
-	public static final fun subscribe (Lkotlinx/coroutines/flow/Flow;)V
-	public static final fun subscribe (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;)V
-	public static final fun subscribe (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function2;Lkotlin/jvm/functions/Function2;)V
-	public static final fun subscribeOn (Lkotlinx/coroutines/flow/Flow;Lkotlin/coroutines/CoroutineContext;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun unsafeTransform (Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function3;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun withContext (Lkotlinx/coroutines/flow/FlowCollector;Lkotlin/coroutines/CoroutineContext;Lkotlin/jvm/functions/Function1;)V
+	public static final fun zip (Lkotlinx/coroutines/flow/Flow;Lkotlinx/coroutines/flow/Flow;Lkotlin/jvm/functions/Function3;)Lkotlinx/coroutines/flow/Flow;
 }
 
 public abstract class kotlinx/coroutines/flow/internal/ChannelFlow : kotlinx/coroutines/flow/Flow {