Tests for partial sync operations

packages/powersync_core/lib/src/database/powersync_db_mixin.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:convert';
 
 import 'package:logging/logging.dart';
 import 'package:meta/meta.dart';
@@ -121,17 +122,56 @@ mixin PowerSyncDatabaseMixin implements SqliteConnection {
 
   Future<void> _updateHasSynced() async {
     // Query the database to see if any data has been synced.
-    final result =
-        await database.get('SELECT powersync_last_synced_at() as synced_at');
-    final timestamp = result['synced_at'] as String?;
-    final hasSynced = timestamp != null;
-
-    if (hasSynced != currentStatus.hasSynced) {
-      final lastSyncedAt =
-          timestamp == null ? null : DateTime.parse('${timestamp}Z').toLocal();
-      final status =
-          SyncStatus(hasSynced: hasSynced, lastSyncedAt: lastSyncedAt);
-      setStatus(status);
+    final result = await database.get('''
+      SELECT CASE
+        WHEN EXISTS (SELECT 1 FROM sqlite_master WHERE name = 'ps_sync_state')
+          THEN (SELECT json_group_array(
+            json_object('prio', priority, 'last_sync', last_synced_at)
+          ) FROM ps_sync_state ORDER BY priority)
+          ELSE powersync_last_synced_at()
+        END AS r;
+    ''');
+    final value = result['r'] as String?;
+    final hasData = value != null;
+
+    DateTime parseDateTime(String sql) {
+      return DateTime.parse('${sql}Z').toLocal();
+    }
+
+    if (hasData) {
+      DateTime? lastCompleteSync;
+      final priorityStatus = <SyncPriorityStatus>[];
+      var hasSynced = false;
+
+      if (value.startsWith('[')) {
+        for (final entry in jsonDecode(value) as List) {
+          final priority = entry['prio'] as int;
+          final lastSyncedAt = parseDateTime(entry['last_sync'] as String);
+
+          if (priority == -1) {
+            hasSynced = true;
+            lastCompleteSync = lastSyncedAt;
+          } else {
+            priorityStatus.add((
+              hasSynced: true,
+              lastSyncedAt: lastSyncedAt,
+              priority: BucketPriority(priority)
+            ));
+          }
+        }
+      } else {
+        hasSynced = true;
+        lastCompleteSync = parseDateTime(value);
+      }
+
+      if (hasSynced != currentStatus.hasSynced) {
+        final status = SyncStatus(
+          hasSynced: hasSynced,
+          lastSyncedAt: lastCompleteSync,
+          statusInPriority: priorityStatus,
+        );
+        setStatus(status);
+      }
     }
   }
 
@@ -201,7 +241,10 @@ mixin PowerSyncDatabaseMixin implements SqliteConnection {
     await disconnect();
     // Now we can close the database
     await database.close();
-    await statusStreamController.close();
+
+    // If there are paused subscriptionso n the status stream, don't delay
+    // closing the database because of that.
+    unawaited(statusStreamController.close());
   }
 
   /// Connect to the PowerSync service, and keep the databases in sync.

packages/powersync_core/lib/src/streaming_sync.dart

@@ -119,6 +119,7 @@ class StreamingSyncImplementation implements StreamingSync {
 
     // Now close the client in all cases not covered above
     _client.close();
+    _statusStreamController.close();
   }
 
   bool get aborted {
@@ -281,7 +282,7 @@ class StreamingSyncImplementation implements StreamingSync {
     for (final (i, priority) in existingPriorityState.indexed) {
       switch (
           BucketPriority.comparator(priority.priority, completed.priority)) {
-        case < 0:
+        case > 0:
           // Entries from here on have a higher priority than the one that was
           // just completed
           final copy = existingPriorityState.toList();
@@ -293,7 +294,7 @@ class StreamingSyncImplementation implements StreamingSync {
           copy[i] = completed;
           _updateStatus(statusInPriority: copy);
           return;
-        case > 0:
+        case < 0:
           continue;
       }
     }
@@ -537,49 +538,55 @@ class StreamingSyncImplementation implements StreamingSync {
     return true;
   }
 
-  Stream<StreamingSyncLine?> streamingSyncRequest(
-      StreamingSyncRequest data) async* {
-    final credentials = await credentialsCallback();
-    if (credentials == null) {
-      throw CredentialsException('Not logged in');
-    }
-    final uri = credentials.endpointUri('sync/stream');
-
-    final request = http.Request('POST', uri);
-    request.headers['Content-Type'] = 'application/json';
-    request.headers['Authorization'] = "Token ${credentials.token}";
-    request.headers.addAll(_userAgentHeaders);
-
-    request.body = convert.jsonEncode(data);
-
-    http.StreamedResponse res;
-    try {
-      // Do not close the client during the request phase - this causes uncaught errors.
-      _safeToClose = false;
-      res = await _client.send(request);
-    } finally {
-      _safeToClose = true;
-    }
-    if (aborted) {
-      return;
-    }
+  Stream<StreamingSyncLine?> streamingSyncRequest(StreamingSyncRequest data) {
+    Future<http.ByteStream?> setup() async {
+      final credentials = await credentialsCallback();
+      if (credentials == null) {
+        throw CredentialsException('Not logged in');
+      }
+      final uri = credentials.endpointUri('sync/stream');
+
+      final request = http.Request('POST', uri);
+      request.headers['Content-Type'] = 'application/json';
+      request.headers['Authorization'] = "Token ${credentials.token}";
+      request.headers.addAll(_userAgentHeaders);
+
+      request.body = convert.jsonEncode(data);
+
+      http.StreamedResponse res;
+      try {
+        // Do not close the client during the request phase - this causes uncaught errors.
+        _safeToClose = false;
+        res = await _client.send(request);
+      } finally {
+        _safeToClose = true;
+      }
+      if (aborted) {
+        return null;
+      }
 
-    if (res.statusCode == 401) {
-      if (invalidCredentialsCallback != null) {
-        await invalidCredentialsCallback!();
+      if (res.statusCode == 401) {
+        if (invalidCredentialsCallback != null) {
+          await invalidCredentialsCallback!();
+        }
       }
-    }
-    if (res.statusCode != 200) {
-      throw await SyncResponseException.fromStreamedResponse(res);
+      if (res.statusCode != 200) {
+        throw await SyncResponseException.fromStreamedResponse(res);
+      }
+
+      return res.stream;
     }
 
-    // Note: The response stream is automatically closed when this loop errors
-    await for (var line in ndjson(res.stream)) {
-      if (aborted) {
-        break;
+    return Stream.fromFuture(setup()).asyncExpand((stream) {
+      if (stream == null || aborted) {
+        return const Stream.empty();
+      } else {
+        return ndjson(stream)
+            .map((line) =>
+                StreamingSyncLine.fromJson(line as Map<String, dynamic>))
+            .takeWhile((_) => !aborted);
       }
-      yield StreamingSyncLine.fromJson(line as Map<String, dynamic>);
-    }
+    });
   }
 
   /// Delays the standard `retryDelay` Duration, but exits early if

packages/powersync_core/lib/src/sync_status.dart

@@ -99,7 +99,15 @@ final class SyncStatus {
 
   /// Returns [lastSyncedAt] and [hasSynced] information for a partial sync
   /// operation, or `null` if the status for that priority is unknown.
-  SyncPriorityStatus? statusForPriority(BucketPriority priority) {
+  ///
+  /// The information returned may be more generic than requested. For instance,
+  /// a completed sync operation (as expressed by [lastSyncedAt]) also
+  /// guarantees that every bucket priority was synchronized before that.
+  /// Similarly, requesting the sync status for priority `1` may return
+  /// information extracted from the lower priority `2` since each partial sync
+  /// in priority `2` necessarily includes a consistent view over data in
+  /// priority `1`.
+  SyncPriorityStatus statusForPriority(BucketPriority priority) {
     assert(statusInPriority.isSortedByCompare(
         (e) => e.priority, BucketPriority.comparator));
 
@@ -112,7 +120,12 @@ final class SyncStatus {
       }
     }
 
-    return null;
+    // If we have a complete sync, that necessarily includes all priorities.
+    return (
+      priority: priority,
+      hasSynced: hasSynced,
+      lastSyncedAt: lastSyncedAt
+    );
   }
 
   @override
@@ -154,8 +167,8 @@ extension type const BucketPriority._(int priorityNumber) {
 /// priority.
 typedef SyncPriorityStatus = ({
   BucketPriority priority,
-  DateTime lastSyncedAt,
-  bool hasSynced,
+  DateTime? lastSyncedAt,
+  bool? hasSynced,
 });
 
 /// Stats of the local upload queue.

packages/powersync_core/lib/src/sync_types.dart

@@ -58,7 +58,11 @@ final class Checkpoint extends StreamingSyncLine {
       'write_checkpoint': writeCheckpoint,
       'buckets': checksums
           .where((c) => priority == null || c.priority <= priority)
-          .map((c) => {'bucket': c.bucket, 'checksum': c.checksum})
+          .map((c) => {
+                'bucket': c.bucket,
+                'checksum': c.checksum,
+                'priority': c.priority,
+              })
           .toList(growable: false)
     };
   }

packages/powersync_core/test/connected_test.dart

@@ -9,7 +9,6 @@ import 'package:powersync_core/powersync_core.dart';
 import 'package:test/test.dart';
 
 import 'server/sync_server/mock_sync_server.dart';
-import 'streaming_sync_test.dart';
 import 'utils/abstract_test_utils.dart';
 import 'utils/test_utils_impl.dart';
 

packages/powersync_core/test/disconnect_test.dart

@@ -1,7 +1,7 @@
 import 'package:powersync_core/powersync_core.dart';
 import 'package:powersync_core/sqlite_async.dart';
 import 'package:test/test.dart';
-import 'streaming_sync_test.dart';
+import 'utils/abstract_test_utils.dart';
 import 'utils/test_utils_impl.dart';
 import 'watch_test.dart';