Improve logging and data emission (DEV) (#1489)

* Cleaner log and remove superfluos removal, if we replace the entry anyways, we don't have to remove it.

* Only propagate changes if the data actually changed.

Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/nearby/modules/calculationtracker/DefaultCalculationTracker.kt

@@ -44,16 +44,13 @@ class DefaultCalculationTracker @Inject constructor(
             flow<Unit> {
                 while (true) {
                     hd.updateSafely {
-                        Timber.v("Running timeout check on: %s", values)
-
                         val timeNow = timeStamper.nowUTC
-                        Timber.v("Time now: %s", timeNow)
+                        Timber.v("Running timeout check (now=%s): %s", timeNow, values)
 
                         mutate {
                             values.filter { it.isCalculating }.toList().forEach {
                                 if (timeNow.isAfter(it.startedAt.plus(TIMEOUT_LIMIT))) {
                                     Timber.w("Calculation timeout on %s", it)
-                                    remove(it.identifier)
                                     this[it.identifier] = it.copy(
                                         finishedAt = timeStamper.nowUTC,
                                         result = Result.TIMEOUT

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/util/flow/HotDataFlow.kt

@@ -9,6 +9,7 @@ import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.channelFlow
 import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.mapNotNull
 import kotlinx.coroutines.flow.onCompletion
 import kotlinx.coroutines.flow.onStart
@@ -51,6 +52,7 @@ class HotDataFlow<T : Any>(
     }
 
     val data: Flow<T> = internalFlow
+        .distinctUntilChanged()
         .onStart { Timber.tag(tag).v("internal onStart") }
         .catch {
             Timber.tag(tag).e(it, "internal Error")

Corona-Warn-App/src/test/java/de/rki/coronawarnapp/util/flow/HotDataFlowTest.kt

@@ -122,6 +122,32 @@ class HotDataFlowTest : BaseTest() {
         coVerify(exactly = 1) { valueProvider.invoke(any()) }
     }
 
+    @Test
+    fun `only emit new values if they actually changed updates`() {
+        val testScope = TestCoroutineScope()
+
+        val hotData = HotDataFlow(
+            loggingTag = "tag",
+            scope = testScope,
+            startValueProvider = { "1" },
+            sharingBehavior = SharingStarted.Lazily
+        )
+
+        val testCollector = hotData.data.test(startOnScope = testScope)
+        testCollector.silent = true
+
+        hotData.updateSafely { "1" }
+        hotData.updateSafely { "2" }
+        hotData.updateSafely { "2" }
+        hotData.updateSafely { "1" }
+
+
+        runBlocking {
+            testCollector.await { list, l -> list.size == 3 }
+            testCollector.latestValues shouldBe listOf("1", "2", "1")
+        }
+    }
+
     @Test
     fun `multiple subscribers share the flow`() {
         val testScope = TestCoroutineScope()