Add a feature flag to reuse the last pos value for initial syncs (#5010)

gradle/libs.versions.toml

@@ -173,7 +173,7 @@ jsoup = "org.jsoup:jsoup:1.21.1"
 appyx_core = { module = "com.bumble.appyx:core", version.ref = "appyx" }
 molecule-runtime = "app.cash.molecule:molecule-runtime:2.1.0"
 timber = "com.jakewharton.timber:timber:5.0.1"
-matrix_sdk = "org.matrix.rustcomponents:sdk-android:25.7.7"
+matrix_sdk = "org.matrix.rustcomponents:sdk-android:25.7.10"
 matrix_richtexteditor = { module = "io.element.android:wysiwyg", version.ref = "wysiwyg" }
 matrix_richtexteditor_compose = { module = "io.element.android:wysiwyg-compose", version.ref = "wysiwyg" }
 sqldelight-driver-android = { module = "app.cash.sqldelight:android-driver", version.ref = "sqldelight" }

libraries/featureflag/api/src/main/kotlin/io/element/android/libraries/featureflag/api/FeatureFlags.kt

@@ -175,4 +175,13 @@ enum class FeatureFlags(
         // False so it's displayed in the developer options screen
         isFinished = false,
     ),
+    SharePos(
+        key = "feature.share_pos",
+        title = "Share pos in sliding sync",
+        description = "Keep the sliding sync pos to make initial syncs faster. Requires an app restart to take effect." +
+            "\n\nWARNING: this may cause issues with syncs.",
+        defaultValue = { false },
+        // False so it's displayed in the developer options screen
+        isFinished = false,
+    ),
 }

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/RustMatrixClientFactory.kt

@@ -78,6 +78,7 @@ class RustMatrixClientFactory @Inject constructor(
         client.setUtdDelegate(UtdTracker(analyticsService))
 
         val syncService = client.syncService()
+            .withSharePos(enable = featureFlagService.isFeatureEnabled(FeatureFlags.SharePos))
             .withOfflineMode()
             .finish()
 

libraries/matrix/impl/src/test/kotlin/io/element/android/libraries/matrix/impl/fixtures/fakes/FakeFfiSyncServiceBuilder.kt

@@ -13,5 +13,6 @@ import org.matrix.rustcomponents.sdk.SyncServiceBuilder
 
 class FakeFfiSyncServiceBuilder : SyncServiceBuilder(NoPointer) {
     override fun withOfflineMode(): SyncServiceBuilder = this
+    override fun withSharePos(enable: Boolean): SyncServiceBuilder = this
     override suspend fun finish(): SyncService = FakeFfiSyncService()
 }