Add User-Agent header.

Author: rkistner

packages/powersync/lib/src/streaming_sync.dart

@@ -5,6 +5,7 @@ import 'package:http/http.dart' as http;
 import 'package:powersync/src/abort_controller.dart';
 import 'package:powersync/src/exceptions.dart';
 import 'package:powersync/src/log_internal.dart';
+import 'package:powersync/src/user_agent/user_agent.dart';
 import 'package:sqlite_async/mutex.dart';
 
 import 'bucket_storage.dart';
@@ -48,6 +49,8 @@ class StreamingSyncImplementation {
 
   final Mutex syncMutex, crudMutex;
 
+  late final String? userAgent;
+
   StreamingSyncImplementation(
       {required this.adapter,
       required this.credentialsCallback,
@@ -65,6 +68,7 @@ class StreamingSyncImplementation {
         crudMutex = Mutex(identifier: "crud-$identifier") {
     _client = client;
     statusStream = _statusStreamController.stream;
+    userAgent = powerSyncUserAgent();
   }
 
   /// Close any active streams.
@@ -195,10 +199,15 @@ class StreamingSyncImplementation {
     }
     final uri = credentials.endpointUri('write-checkpoint2.json');
 
-    final response = await _client.get(uri, headers: {
+    Map<String, String> headers = {
       'Content-Type': 'application/json',
       'Authorization': "Token ${credentials.token}"
-    });
+    };
+    if (userAgent != null) {
+      headers['User-Agent'] = userAgent!;
+    }
+
+    final response = await _client.get(uri, headers: headers);
     if (response.statusCode == 401) {
       if (invalidCredentialsCallback != null) {
         await invalidCredentialsCallback!();
@@ -405,6 +414,9 @@ class StreamingSyncImplementation {
     final request = http.Request('POST', uri);
     request.headers['Content-Type'] = 'application/json';
     request.headers['Authorization'] = "Token ${credentials.token}";
+    if (userAgent != null) {
+      request.headers['User-Agent'] = userAgent!;
+    }
     request.body = convert.jsonEncode(data);
 
     http.StreamedResponse res;

packages/powersync/lib/src/user_agent/user_agent.dart

@@ -0,0 +1,6 @@
+// For native, expose a user agent.
+// For web, we're not able to override the user agent anyway.
+
+export './user_agent_stub.dart'
+    // ignore: uri_does_not_exist
+    if (dart.library.io) './user_agent_native.dart';

packages/powersync/lib/src/user_agent/user_agent_native.dart

@@ -0,0 +1,14 @@
+import 'dart:io';
+
+import 'package:powersync/src/version.dart';
+
+String? powerSyncUserAgent() {
+  var dartVersion = RegExp(r'[\w.]+').stringMatch(Platform.version);
+  var dart = 'Dart';
+  if (dartVersion != null) {
+    dart = "Dart/$dartVersion";
+  }
+  // Ideally we'd get an OS version, but that's quite complex.
+
+  return 'PowerSync/$libraryVersion ($dart; ${Platform.operatingSystem})';
+}

packages/powersync/lib/src/user_agent/user_agent_stub.dart

@@ -0,0 +1,3 @@
+String? powerSyncUserAgent() {
+  return null;
+}

packages/powersync/lib/src/version.dart

@@ -0,0 +1,2 @@
+// TODO: auto-update when bumping the version
+const libraryVersion = '1.6.4';