+str #22711 adding GroupedWeightedWithin

akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala

@@ -981,16 +981,37 @@ trait FlowOps[+Out, +Mat] {
    * `n` must be positive, and `d` must be greater than 0 seconds, otherwise
    * IllegalArgumentException is thrown.
    *
-   * '''Emits when''' the configured time elapses since the last group has been emitted
+   * '''Emits when''' the configured time elapses since the last group has been emitted or `n` elements is buffered
    *
-   * '''Backpressures when''' the configured time elapses since the last group has been emitted
+   * '''Backpressures when''' downstream backpressures, and there are `n+1` buffered elements
    *
    * '''Completes when''' upstream completes (emits last group)
    *
    * '''Cancels when''' downstream completes
    */
   def groupedWithin(n: Int, d: FiniteDuration): Repr[immutable.Seq[Out]] =
-    via(new GroupedWithin[Out](n, d))
+    via(new GroupedWeightedWithin[Out](n, ConstantFun.oneLong, d).withAttributes(DefaultAttributes.groupedWithin))
+
+  /**
+   * Chunk up this stream into groups of elements received within a time window,
+   * or limited by the weight of the elements, whatever happens first.
+   * Empty groups will not be emitted if no elements are received from upstream.
+   * The last group before end-of-stream will contain the buffered elements
+   * since the previously emitted group.
+   *
+   * `maxWeight` must be positive, and `d` must be greater than 0 seconds, otherwise
+   * IllegalArgumentException is thrown.
+   *
+   * '''Emits when''' the configured time elapses since the last group has been emitted or weight limit reached
+   *
+   * '''Backpressures when''' downstream backpressures, and buffered group (+ pending element) weighs more than `maxWeight`
+   *
+   * '''Completes when''' upstream completes (emits last group)
+   *
+   * '''Cancels when''' downstream completes
+   */
+  def groupedWeightedWithin(maxWeight: Long, d: FiniteDuration)(costFn: Out ⇒ Long): Repr[immutable.Seq[Out]] =
+    via(new GroupedWeightedWithin[Out](maxWeight, costFn, d))
 
   /**
    * Shifts elements emission in time by a specified amount. It allows to store elements