Fix #6782. Ensure SyncThread is started

matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/session/sync/SyncService.kt

@@ -53,6 +53,11 @@ interface SyncService {
      */
     fun getSyncState(): SyncState
 
+    /**
+     * This method returns true if the sync thread is alive, i.e. started.
+     */
+    fun isSyncThreadAlive(): Boolean
+
     /**
      * This method allows to listen the sync state.
      * @return a [LiveData] of [SyncState].

matrix-sdk-android/src/main/java/org/matrix/android/sdk/internal/session/sync/DefaultSyncService.kt

@@ -73,6 +73,8 @@ internal class DefaultSyncService @Inject constructor(
 
     override fun getSyncState() = getSyncThread().currentState()
 
+    override fun isSyncThreadAlive() = getSyncThread().isAlive
+
     override fun getSyncRequestStateFlow() = syncRequestStateTracker.syncRequestState
 
     override fun hasAlreadySynced(): Boolean {

vector/src/main/java/im/vector/app/core/di/ActiveSessionHolder.kt

@@ -20,6 +20,7 @@ import android.content.Context
 import arrow.core.Option
 import im.vector.app.ActiveSessionDataSource
 import im.vector.app.core.extensions.configureAndStart
+import im.vector.app.core.extensions.startSyncing
 import im.vector.app.core.pushers.UnifiedPushHelper
 import im.vector.app.core.services.GuardServiceStarter
 import im.vector.app.features.call.webrtc.WebRtcCallManager
@@ -100,10 +101,16 @@ class ActiveSessionHolder @Inject constructor(
     }
 
     suspend fun getOrInitializeSession(startSync: Boolean): Session? {
-        return activeSessionReference.get() ?: sessionInitializer.tryInitialize(readCurrentSession = { activeSessionReference.get() }) { session ->
-            setActiveSession(session)
-            session.configureAndStart(applicationContext, startSyncing = startSync)
-        }
+        return activeSessionReference.get()
+                ?.also {
+                    if (startSync && !it.syncService().isSyncThreadAlive()) {
+                        it.startSyncing(applicationContext)
+                    }
+                }
+                ?: sessionInitializer.tryInitialize(readCurrentSession = { activeSessionReference.get() }) { session ->
+                    setActiveSession(session)
+                    session.configureAndStart(applicationContext, startSyncing = startSync)
+                }
     }
 
     fun isWaitingForSessionInitialization() = activeSessionReference.get() == null && authenticationService.hasAuthenticatedSessions()