Rename scan to accumulate, get rid of lambda with initial value

Author: qwwdfsad

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

@@ -856,7 +856,6 @@ public final class kotlinx/coroutines/flow/FlowKt {
 	public static final fun retry (Lkotlinx/coroutines/flow/Flow;ILkotlin/jvm/functions/Function1;)Lkotlinx/coroutines/flow/Flow;
 	public static synthetic fun retry$default (Lkotlinx/coroutines/flow/Flow;ILkotlin/jvm/functions/Function1;ILjava/lang/Object;)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;Lkotlin/jvm/functions/Function0;Lkotlin/jvm/functions/Function3;)Lkotlinx/coroutines/flow/Flow;
 	public static final fun scan (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;

kotlinx-coroutines-core/common/src/flow/operators/Transform.kt

@@ -102,7 +102,9 @@ public fun <T> Flow<T>.onEach(action: suspend (T) -> Unit): Flow<T> = flow {
 
 /**
  * Reduces the given flow with [operation], emitting every intermediate result, including initial value.
- * The first element is takes as initial value for operation accumulator.
+ * The first element is taken as initial value for operation accumulator.
+ * This operator has a sibling with initial value -- [accumulate].
+ *
  * For example:
  * ```
  * flowOf(1, 2, 3, 4).scan { (v1, v2) -> v1 + v2 }.toList()
@@ -123,17 +125,17 @@ public fun <T> Flow<T>.scan(operation: suspend (accumulator: T, value: T) -> T):
 }
 
 /**
- * Reduces the given flow with [operation], emitting every intermediate result, including initial value.
- * An initial value is provided lazily by [initialSupplier] and is always immediately emitted.
+ * Reduces the given flow with [operation], emitting every intermediate result, including [initial] value.
+ * Note that initial value should be immutable (or should not be mutated) as it is shared between different collectors.
  * For example:
  * ```
- * flowOf(1, 2, 3).scan(::emptyList) { acc: List<Int>, value -> acc + value }.toList()
+ * flowOf(1, 2, 3).accumulate(emptyList<Int>()) { acc, value -> acc + value }.toList()
  * ```
  * will produce `[], [1], [1, 2], [1, 2, 3]]`.
  */
 @FlowPreview
-public fun <T, R> Flow<T>.scan(initialSupplier: () -> R, @BuilderInference operation: suspend (accumulator: R, value: T) -> R): Flow<R> = flow {
-    var accumulator: R = initialSupplier()
+public fun <T, R> Flow<T>.accumulate(initial: R, @BuilderInference operation: suspend (accumulator: R, value: T) -> R): Flow<R> = flow {
+    var accumulator: R = initial
     emit(accumulator)
     collect { value ->
         accumulator = operation(accumulator, value)

kotlinx-coroutines-core/common/src/flow/terminal/Collect.kt

@@ -37,4 +37,4 @@ public suspend inline fun <T> Flow<T>.collect(crossinline action: suspend (value
  * Collects all the values from the given [flow] and emits them to the collector.
  * Shortcut for `flow.collect { value -> emit(value) }`.
  */
-public suspend inline fun <T> FlowCollector<T>.emitAll(flow: Flow<T>) = flow.collect { value -> emit(value) }
+public suspend inline fun <T> FlowCollector<T>.emitAll(flow: Flow<T>) = flow.collect(this)

kotlinx-coroutines-core/common/test/flow/operators/ScanTest.kt

@@ -19,7 +19,7 @@ class ScanTest : TestBase() {
     @Test
     fun testScanWithInitial() = runTest {
         val flow = flowOf(1, 2, 3)
-        val result = flow.scan(::emptyList) { acc: List<Int>, value -> acc + value }.toList()
+        val result = flow.accumulate(emptyList<Int>()) { acc, value -> acc + value }.toList()
         assertEquals(listOf(emptyList(), listOf(1), listOf(1, 2), listOf(1, 2, 3)), result)
     }