feat: Custom App Metadata

demos/supabase-todolist/lib/powersync.dart

@@ -153,7 +153,9 @@ Future<String> getDatabasePath() async {
   return join(dir.path, dbFilename);
 }
 
-const options = SyncOptions(syncImplementation: SyncClientImplementation.rust);
+const options = SyncOptions(
+    syncImplementation: SyncClientImplementation.rust,
+    appMetadata: {'app_version': '1.0.1'});
 
 Future<void> openDatabase() async {
   // Open the local database

packages/powersync_core/lib/src/sync/options.dart

@@ -3,6 +3,11 @@ import 'package:meta/meta.dart';
 
 /// Options that affect how the sync client connects to the sync service.
 final class SyncOptions {
+  /// A map of application metadata that is passed to the PowerSync service.
+  ///
+  /// Application metadata that will be displayed in PowerSync service logs.
+  final Map<String, String>? appMetadata;
+
   /// A JSON object that is passed to the sync service and forwarded to sync
   /// rules.
   ///
@@ -39,19 +44,22 @@ final class SyncOptions {
     this.params,
     this.syncImplementation = SyncClientImplementation.defaultClient,
     this.includeDefaultStreams,
+    this.appMetadata,
   });
 
   SyncOptions _copyWith({
     Duration? crudThrottleTime,
     Duration? retryDelay,
     Map<String, dynamic>? params,
+    Map<String, String>? appMetadata,
   }) {
     return SyncOptions(
       crudThrottleTime: crudThrottleTime ?? this.crudThrottleTime,
       retryDelay: retryDelay,
       params: params ?? this.params,
       syncImplementation: syncImplementation,
       includeDefaultStreams: includeDefaultStreams,
+      appMetadata: appMetadata ?? this.appMetadata,
     );
   }
 }
@@ -88,14 +96,18 @@ extension type ResolvedSyncOptions(SyncOptions source) {
     Duration? crudThrottleTime,
     Duration? retryDelay,
     Map<String, dynamic>? params,
+    Map<String, String>? appMetadata,
   }) {
     return ResolvedSyncOptions((source ?? SyncOptions())._copyWith(
       crudThrottleTime: crudThrottleTime,
       retryDelay: retryDelay,
       params: params,
+      appMetadata: appMetadata,
     ));
   }
 
+  Map<String, String> get appMetadata => source.appMetadata ?? const {};
+
   Duration get crudThrottleTime =>
       source.crudThrottleTime ?? const Duration(milliseconds: 10);
 
@@ -113,13 +125,15 @@ extension type ResolvedSyncOptions(SyncOptions source) {
       syncImplementation: other.syncImplementation,
       includeDefaultStreams:
           other.includeDefaultStreams ?? includeDefaultStreams,
+      appMetadata: other.appMetadata ?? appMetadata,
     );
 
     final didChange = !_mapEquality.equals(newOptions.params, params) ||
         newOptions.crudThrottleTime != crudThrottleTime ||
         newOptions.retryDelay != retryDelay ||
         newOptions.syncImplementation != source.syncImplementation ||
-        newOptions.includeDefaultStreams != includeDefaultStreams;
+        newOptions.includeDefaultStreams != includeDefaultStreams ||
+        !_mapEquality.equals(newOptions.appMetadata, appMetadata);
     return (ResolvedSyncOptions(newOptions), didChange);
   }
 

packages/powersync_core/lib/src/sync/protocol.dart

@@ -247,15 +247,18 @@ class StreamingSyncRequest {
   bool includeChecksum = true;
   String clientId;
   Map<String, dynamic>? parameters;
+  Map<String, String>? appMetadata;
 
-  StreamingSyncRequest(this.buckets, this.parameters, this.clientId);
+  StreamingSyncRequest(
+      this.buckets, this.parameters, this.clientId, this.appMetadata);
 
   Map<String, dynamic> toJson() {
     final Map<String, dynamic> json = {
       'buckets': buckets,
       'include_checksum': includeChecksum,
       'raw_data': true,
-      'client_id': clientId
+      'client_id': clientId,
+      'app_metadata': appMetadata,
     };
 
     if (parameters != null) {

packages/powersync_core/lib/src/sync/streaming_sync.dart

@@ -12,14 +12,14 @@ import 'package:powersync_core/src/sync/options.dart';
 import 'package:powersync_core/src/user_agent/user_agent.dart';
 import 'package:sqlite_async/mutex.dart';
 
-import 'bucket_storage.dart';
 import '../crud.dart';
+import 'bucket_storage.dart';
 import 'instruction.dart';
 import 'internal_connector.dart';
 import 'mutable_sync_status.dart';
+import 'protocol.dart';
 import 'stream_utils.dart';
 import 'sync_status.dart';
-import 'protocol.dart';
 
 typedef SubscribedStream = ({String name, String parameters});
 
@@ -339,8 +339,8 @@ class StreamingSyncImplementation implements StreamingSync {
 
     Checkpoint? targetCheckpoint;
 
-    var requestStream = _streamingSyncRequest(
-            StreamingSyncRequest(bucketRequests, options.params, clientId!))
+    var requestStream = _streamingSyncRequest(StreamingSyncRequest(
+            bucketRequests, options.params, clientId!, options.appMetadata))
         .map(ReceivedLine.new);
 
     var merged = addBroadcast(requestStream, _nonLineSyncEvents.stream);
@@ -633,6 +633,7 @@ final class _ActiveRustStreamingIteration {
       await _control(
         'start',
         convert.json.encode({
+          'app_metadata': sync.options.appMetadata,
           'parameters': sync.options.params,
           'schema': convert.json.decode(sync.schemaJson),
           'include_defaults': sync.options.includeDefaultStreams,

packages/powersync_core/lib/src/web/sync_worker.dart

@@ -94,6 +94,11 @@ class _ConnectedClient {
                 null => SyncClientImplementation.defaultClient,
                 final name => SyncClientImplementation.values.byName(name),
               },
+              appMetadata: switch (request.appMetadataEncoded) {
+                null => null,
+                final encodedAppMetadata => Map<String, String>.from(
+                    jsonDecode(encodedAppMetadata) as Map<String, dynamic>),
+              },
             );
 
             _runner = _worker.referenceSyncTask(

packages/powersync_core/lib/src/web/sync_worker_protocol.dart

@@ -80,6 +80,7 @@ extension type StartSynchronization._(JSObject _) implements JSObject {
     required String schemaJson,
     String? syncParamsEncoded,
     UpdateSubscriptions? subscriptions,
+    String? appMetadataEncoded,
   });
 
   external String get databaseName;
@@ -90,6 +91,7 @@ extension type StartSynchronization._(JSObject _) implements JSObject {
   external String get schemaJson;
   external String? get syncParamsEncoded;
   external UpdateSubscriptions? get subscriptions;
+  external String? get appMetadataEncoded;
 }
 
 @anonymous
@@ -483,6 +485,10 @@ final class WorkerCommunicationChannel {
           final params => jsonEncode(params),
         },
         subscriptions: UpdateSubscriptions(-1, streams),
+        appMetadataEncoded: switch (options.source.appMetadata) {
+          null => null,
+          final appMetadata => jsonEncode(appMetadata),
+        },
       ),
     ));
     await completion;

packages/powersync_core/test/sync/stream_test.dart

@@ -4,7 +4,6 @@ import 'dart:convert';
 import 'package:async/async.dart';
 import 'package:logging/logging.dart';
 import 'package:powersync_core/powersync_core.dart';
-
 import 'package:test/test.dart';
 
 import '../server/sync_server/in_memory_sync_server.dart';
@@ -260,4 +259,41 @@ void main() {
     );
     a.unsubscribe();
   });
+
+  test('passes app metadata to the server (rust)', () async {
+    options = SyncOptions(
+      syncImplementation: SyncClientImplementation.rust,
+      appMetadata: {'foo': 'bar'},
+    );
+
+    await waitForConnection();
+
+    final request = await syncService.waitForListener;
+    expect(
+      json.decode(await request.readAsString()),
+      containsPair(
+        'app_metadata',
+        containsPair('foo', 'bar'),
+      ),
+    );
+  });
+
+  test('passes app metadata to the server (legacy sync client)', () async {
+    options = SyncOptions(
+      // ignore: deprecated_member_use_from_same_package
+      syncImplementation: SyncClientImplementation.dart,
+      appMetadata: {'foo': 'bar'},
+    );
+
+    await waitForConnection();
+
+    final request = await syncService.waitForListener;
+    expect(
+      json.decode(await request.readAsString()),
+      containsPair(
+        'app_metadata',
+        containsPair('foo', 'bar'),
+      ),
+    );
+  });
 }