Docs: Source.repeat (and friends) (#28615)

akka-docs/src/main/paradox/stream/operators/Source/repeat.md

@@ -1,20 +1,34 @@
 # Source.repeat
 
-Stream a single object repeatedly
+Stream a single object repeatedly.
 
 @ref[Source operators](../index.md#source-operators)
 
-@@@div { .group-scala }
-
 ## Signature
 
-@@signature [Source.scala](/akka-stream/src/main/scala/akka/stream/scaladsl/Source.scala) { #repeat }
-
-@@@
+@apidoc[Source.repeat](Source$) { scala="#repeat[T](element:T):akka.stream.scaladsl.Source[T,akka.NotUsed]" java="#repeat(T)" }
 
 ## Description
 
-Stream a single object repeatedly
+This source emits a single element repeatedly. It never completes, if you want the stream to be finite you will need to limit it by combining with another operator
+
+See also:
+
+* @ref:[`single`](single.md) Stream a single object once.
+* @ref:[`tick`](tick.md) A periodical repetition of an arbitrary object.
+* @ref:[`cycle`](cycle.md) Stream iterator in cycled manner.
+
+## Example
+
+This example prints the first 4 elements emitted by `Source.repeat`.
+
+Scala
+:  @@snip [snip](/akka-stream-tests/src/test/scala/akka/stream/scaladsl/SourceSpec.scala) { #repeat }
+
+Java
+:  @@snip [snip](/akka-stream-tests/src/test/java/akka/stream/javadsl/SourceTest.java) { #repeat }
+
+
 
 ## Reactive Streams semantics
 

akka-docs/src/main/paradox/stream/operators/Source/single.md

@@ -1,20 +1,22 @@
 # Source.single
 
-Stream a single object
+Stream a single object once.
 
 @ref[Source operators](../index.md#source-operators)
 
-@@@div { .group-scala }
-
 ## Signature
 
-@@signature [Source.scala](/akka-stream/src/main/scala/akka/stream/scaladsl/Source.scala) { #single }
-
-@@@
+@apidoc[Source.single](Source$) { scala="#single[T](element:T):akka.stream.scaladsl.Source[T,akka.NotUsed]" java="#single(T)" }
 
 ## Description
 
-Stream a single object
+Stream a single object once and complete after thereafter.
+
+See also:
+
+* @ref:[`repeat`](repeat.md) Stream a single object repeatedly.
+* @ref:[`tick`](tick.md) A periodical repetition of an arbitrary object.
+* @ref:[`cycle`](cycle.md) Stream iterator in cycled manner.
 
 ## Examples
 

akka-docs/src/main/paradox/stream/operators/Source/tick.md

@@ -28,6 +28,11 @@ example for achieving a periodical element that changes over time.
 
 @@@
 
+See also:
+
+* @ref:[`repeat`](repeat.md) Stream a single object repeatedly.
+* @ref:[`cycle`](cycle.md) Stream iterator in cycled manner.
+
 ## Examples
 
 This first example prints to standard out periodically:

akka-docs/src/main/paradox/stream/operators/index.md

@@ -37,8 +37,8 @@ These built-in sources are available from @scala[`akka.stream.scaladsl.Source`]
 |Source|<a name="maybe"></a>@ref[maybe](Source/maybe.md)|Create a source that emits once the materialized @scala[`Promise`] @java[`CompletableFuture`] is completed with a value.|
 |Source|<a name="queue"></a>@ref[queue](Source/queue.md)|Materialize a `SourceQueue` onto which elements can be pushed for emitting from the source. |
 |Source|<a name="range"></a>@ref[range](Source/range.md)|Emit each integer in a range, with an option to take bigger steps than 1.|
-|Source|<a name="repeat"></a>@ref[repeat](Source/repeat.md)|Stream a single object repeatedly|
-|Source|<a name="single"></a>@ref[single](Source/single.md)|Stream a single object|
+|Source|<a name="repeat"></a>@ref[repeat](Source/repeat.md)|Stream a single object repeatedly.|
+|Source|<a name="single"></a>@ref[single](Source/single.md)|Stream a single object once.|
 |Source|<a name="tick"></a>@ref[tick](Source/tick.md)|A periodical repetition of an arbitrary object.|
 |Source|<a name="unfold"></a>@ref[unfold](Source/unfold.md)|Stream the result of a function as long as it returns a @scala[`Some`] @java[non empty `Optional`].|
 |Source|<a name="unfoldasync"></a>@ref[unfoldAsync](Source/unfoldAsync.md)|Just like `unfold` but the fold function returns a @scala[`Future`] @java[`CompletionStage`].|

akka-stream-tests/src/test/java/akka/stream/javadsl/SourceTest.java

@@ -626,6 +626,20 @@ public class SourceTest extends StreamTest {
     for (Integer i : result) assertEquals(i, (Integer) 42);
   }
 
+  @Test
+  public void mustRepeatForDocs() throws Exception {
+    // #repeat
+    Source<Integer, NotUsed> source = Source.repeat(42);
+    CompletionStage<Done> f = source.take(4).runWith(Sink.foreach(System.out::println), system);
+    // 42
+    // 42
+    // 42
+    // 42
+    // #repeat
+    final Done result = f.toCompletableFuture().get(3, TimeUnit.SECONDS);
+    assertEquals(Done.done(), result);
+  }
+
   @Test
   public void mustBeAbleToUseQueue() throws Exception {
     final Pair<SourceQueueWithComplete<String>, CompletionStage<List<String>>> x =

akka-stream-tests/src/test/scala/akka/stream/scaladsl/SourceSpec.scala

@@ -4,6 +4,7 @@
 
 package akka.stream.scaladsl
 
+import akka.Done
 import akka.stream.testkit.Utils.TE
 import akka.testkit.DefaultTimeout
 import com.github.ghik.silencer.silent
@@ -215,6 +216,18 @@ class SourceSpec extends StreamSpec with DefaultTimeout {
       f.futureValue.size should ===(1000)
       f.futureValue.toSet should ===(Set(42))
     }
+
+    "repeat example" in {
+      // #repeat
+      val source: Source[Int, NotUsed] = Source.repeat(42)
+      val f = source.take(4).runWith(Sink.foreach(println))
+      // 42
+      // 42
+      // 42
+      // 42
+      // #repeat
+      f.futureValue shouldBe Done
+    }
   }
 
   "Unfold Source" must {