background time nullable (#6886)

Make background time nullable
For each new session generated, reset background time
Update unit tests

Author: themiswang

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/SessionData.kt

@@ -27,7 +27,10 @@ import kotlinx.serialization.json.Json
 
 /** Session data to be persisted. */
 @Serializable
-internal data class SessionData(val sessionDetails: SessionDetails, val backgroundTime: Time)
+internal data class SessionData(
+  val sessionDetails: SessionDetails,
+  val backgroundTime: Time? = null
+)
 
 /** DataStore json [Serializer] for [SessionData]. */
 @Singleton
@@ -38,11 +41,7 @@ constructor(
   private val timeProvider: TimeProvider,
 ) : Serializer<SessionData> {
   override val defaultValue: SessionData
-    get() =
-      SessionData(
-        sessionDetails = sessionGenerator.generateNewSession(currentSession = null),
-        backgroundTime = timeProvider.currentTime(),
-      )
+    get() = SessionData(sessionGenerator.generateNewSession(currentSession = null))
 
   override suspend fun readFrom(input: InputStream): SessionData =
     try {

firebase-sessions/src/main/kotlin/com/google/firebase/sessions/SharedSessionRepository.kt

@@ -62,14 +62,13 @@ constructor(
   internal var previousNotificationType: NotificationType = NotificationType.GENERAL
 
   init {
-    println("session repo init")
     CoroutineScope(backgroundDispatcher).launch {
       sessionDataStore.data
         .catch {
           val newSession =
             SessionData(
               sessionDetails = sessionGenerator.generateNewSession(null),
-              backgroundTime = timeProvider.currentTime()
+              backgroundTime = null
             )
           Log.d(
             TAG,
@@ -123,15 +122,16 @@ constructor(
               val newSessionDetails =
                 sessionGenerator.generateNewSession(sessionData.sessionDetails)
               sessionFirelogPublisher.mayLogSession(sessionDetails = newSessionDetails)
-              currentSessionData.copy(sessionDetails = newSessionDetails)
+              currentSessionData.copy(sessionDetails = newSessionDetails, backgroundTime = null)
             } else {
               currentSessionData
             }
           }
         } catch (ex: Exception) {
           Log.d(TAG, "App appForegrounded, failed to update data. Message: ${ex.message}")
           val newSessionDetails = sessionGenerator.generateNewSession(sessionData.sessionDetails)
-          localSessionData = localSessionData.copy(sessionDetails = newSessionDetails)
+          localSessionData =
+            localSessionData.copy(sessionDetails = newSessionDetails, backgroundTime = null)
           sessionFirelogPublisher.mayLogSession(sessionDetails = newSessionDetails)
 
           val sessionId = newSessionDetails.sessionId
@@ -159,8 +159,12 @@ constructor(
   }
 
   private fun shouldInitiateNewSession(sessionData: SessionData): Boolean {
-    val interval = timeProvider.currentTime() - sessionData.backgroundTime
-    return interval > sessionsSettings.sessionRestartTimeout
+    sessionData.backgroundTime?.let {
+      val interval = timeProvider.currentTime() - it
+      return interval > sessionsSettings.sessionRestartTimeout
+    }
+    Log.d(TAG, "No process has backgrounded yet, should not change the session.")
+    return false
   }
 
   private companion object {

firebase-sessions/src/test/kotlin/com/google/firebase/sessions/SharedSessionRepositoryTest.kt

@@ -33,7 +33,6 @@ import com.google.firebase.sessions.testing.FakeUuidGenerator
 import kotlin.time.Duration.Companion.hours
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.asCoroutineDispatcher
-import kotlinx.coroutines.launch
 import kotlinx.coroutines.test.runCurrent
 import kotlinx.coroutines.test.runTest
 import org.junit.After
@@ -135,7 +134,7 @@ class SharedSessionRepositoryTest {
   }
 
   @Test
-  fun appForegroundSharedSessionRepo_updateSuccess() = runTest {
+  fun appForegroundGenerateNewSession_updateSuccess() = runTest {
     val sessionFirelogPublisher =
       SessionFirelogPublisherImpl(
         fakeFirebaseApp.firebaseApp,
@@ -166,20 +165,22 @@ class SharedSessionRepositoryTest {
         backgroundDispatcher =
           TestOnlyExecutors.background().asCoroutineDispatcher() + coroutineContext
       )
-    backgroundScope.launch {
-      fakeTimeProvider.addInterval(20.hours)
-      sharedSessionRepository.appForeground()
-    }
     runCurrent()
+
+    fakeTimeProvider.addInterval(20.hours)
+    sharedSessionRepository.appForeground()
+    runCurrent()
+
     assertThat(sharedSessionRepository.localSessionData.sessionDetails.sessionId)
       .isEqualTo(SESSION_ID_1)
+    assertThat(sharedSessionRepository.localSessionData.backgroundTime).isNull()
     assertThat(sharedSessionRepository.previousNotificationType)
       .isEqualTo(SharedSessionRepositoryImpl.NotificationType.GENERAL)
     fakeDataStore.close()
   }
 
   @Test
-  fun appForegroundSharedSessionRepo_updateFail() = runTest {
+  fun appForegroundGenerateNewSession_updateFail() = runTest {
     val sessionFirelogPublisher =
       SessionFirelogPublisherImpl(
         fakeFirebaseApp.firebaseApp,
@@ -201,7 +202,6 @@ class SharedSessionRepositoryTest {
         ),
         IllegalArgumentException("Datastore init failed")
       )
-    fakeDataStore.throwOnNextUpdateData(IllegalArgumentException("Datastore update failed"))
     val sharedSessionRepository =
       SharedSessionRepositoryImpl(
         sessionsSettings,
@@ -212,15 +212,23 @@ class SharedSessionRepositoryTest {
         backgroundDispatcher =
           TestOnlyExecutors.background().asCoroutineDispatcher() + coroutineContext
       )
+    runCurrent()
 
-    backgroundScope.launch {
-      fakeTimeProvider.addInterval(20.hours)
-      sharedSessionRepository.appForeground()
-    }
+    // set background time first
+    fakeDataStore.throwOnNextUpdateData(IllegalArgumentException("Datastore update failed"))
+    sharedSessionRepository.appBackground()
     runCurrent()
+
+    // foreground update session
+    fakeTimeProvider.addInterval(20.hours)
+    fakeDataStore.throwOnNextUpdateData(IllegalArgumentException("Datastore update failed"))
+    sharedSessionRepository.appForeground()
+    runCurrent()
+
     // session_2 here because session_1 is failed when try to init datastore
     assertThat(sharedSessionRepository.localSessionData.sessionDetails.sessionId)
       .isEqualTo(SESSION_ID_2)
+    assertThat(sharedSessionRepository.localSessionData.backgroundTime).isNull()
     assertThat(sharedSessionRepository.previousNotificationType)
       .isEqualTo(SharedSessionRepositoryImpl.NotificationType.FALLBACK)
     fakeDataStore.close()