make Bottom[LastWriterWins] not overwrite an earlier created value

rescala-lang · Mar 25, 2024 · 4c98fee · 4c98fee
1 parent 4bc3247
commit 4c98fee
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diff --git a/Modules/RDTs/src/main/scala/rdts/datatypes/LastWriterWins.scala b/Modules/RDTs/src/main/scala/rdts/datatypes/LastWriterWins.scala
@@ -28,7 +28,7 @@ case class LastWriterWins[+A](timestamp: CausalTime, payload: A) {
 
 object LastWriterWins {
 
-  def empty[A: Bottom]: LastWriterWins[A] = now(Bottom.empty)
+  def empty[A: Bottom]: LastWriterWins[A] = LastWriterWins(Bottom[CausalTime].empty, Bottom[A].empty)
 
   def fallback[A](v: A): LastWriterWins[A] =
     LastWriterWins(rdts.time.CausalTime(Long.MinValue, 0, CausalTime.countedTime()), v)

diff --git a/Modules/RDTs/src/test/scala/test/rdts/bespoke/LastWriterWinsTest.scala b/Modules/RDTs/src/test/scala/test/rdts/bespoke/LastWriterWinsTest.scala
@@ -35,4 +35,17 @@ class LastWriterWinsTest extends munit.FunSuite {
     assertEquals(merged.read, "Hello Distributed World")
   }
 
+  test("newer Bottom does not overwrite an earlier initial value") {
+    import LastWriterWins.given
+
+    val lww1 = LastWriterWins.now("Hello Distributed World")
+    val lww2 = Bottom[LastWriterWins[String]].empty
+
+    assertNotEquals(lww1.timestamp, lww2.timestamp)
+
+    val merged = lww1 merge lww2
+
+    assertEquals(merged.read, "Hello Distributed World")
+  }
+
 }