Use X-User-Agent on web.

Author: rkistner

packages/powersync/lib/src/streaming_sync.dart

@@ -49,7 +49,8 @@ class StreamingSyncImplementation {
 
   final Mutex syncMutex, crudMutex;
 
-  late final String? userAgent;
+  final Map<String, String> _userAgentHeaders;
+
   String? clientId;
 
   StreamingSyncImplementation(
@@ -66,10 +67,10 @@ class StreamingSyncImplementation {
       /// A good value is typically the DB file path which it will mutate when syncing.
       String? identifier = "unknown"})
       : syncMutex = Mutex(identifier: "sync-$identifier"),
-        crudMutex = Mutex(identifier: "crud-$identifier") {
+        crudMutex = Mutex(identifier: "crud-$identifier"),
+        _userAgentHeaders = userAgentHeaders() {
     _client = client;
     statusStream = _statusStreamController.stream;
-    userAgent = powerSyncUserAgent();
   }
 
   /// Close any active streams.
@@ -204,11 +205,9 @@ class StreamingSyncImplementation {
     Map<String, String> headers = {
       'Content-Type': 'application/json',
       'Authorization': "Token ${credentials.token}",
-      'Client-ID': clientId!
+      'Client-ID': clientId!,
+      ..._userAgentHeaders
     };
-    if (userAgent != null) {
-      headers['User-Agent'] = userAgent!;
-    }
 
     final response = await _client.get(uri, headers: headers);
     if (response.statusCode == 401) {
@@ -417,9 +416,8 @@ class StreamingSyncImplementation {
     request.headers['Content-Type'] = 'application/json';
     request.headers['Authorization'] = "Token ${credentials.token}";
     request.headers['Client-ID'] = clientId!;
-    if (userAgent != null) {
-      request.headers['User-Agent'] = userAgent!;
-    }
+    request.headers.addAll(_userAgentHeaders);
+
     request.body = convert.jsonEncode(data);
 
     http.StreamedResponse res;

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

@@ -1,6 +1,5 @@
-// 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';
+    if (dart.library.io) './user_agent_native.dart'
+    // ignore: uri_does_not_exist
+    if (dart.library.html) './user_agent_web.dart';

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

@@ -2,7 +2,7 @@ import 'dart:io';
 
 import 'package:powersync/src/version.dart';
 
-String? powerSyncUserAgent() {
+String powerSyncUserAgent() {
   var dartVersion = RegExp(r'[\w.]+').stringMatch(Platform.version);
   var dart = 'Dart';
   if (dartVersion != null) {
@@ -12,3 +12,7 @@ String? powerSyncUserAgent() {
   // Platform.operatingSystemVersion is very verbose.
   return 'powersync-dart/$libraryVersion ($dart; ${Platform.operatingSystem})';
 }
+
+Map<String, String> userAgentHeaders() {
+  return {'User-Agent': powerSyncUserAgent()};
+}

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

@@ -1,3 +1,7 @@
-String? powerSyncUserAgent() {
-  return null;
+String powerSyncUserAgent() {
+  return '';
+}
+
+Map<String, String> userAgentHeaders() {
+  return {};
 }

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

@@ -0,0 +1,12 @@
+import 'package:powersync/src/version.dart';
+
+String powerSyncUserAgent() {
+  return 'powersync-dart/$libraryVersion (flutter-web)';
+}
+
+Map<String, String> userAgentHeaders() {
+  var ua = powerSyncUserAgent();
+  // Chrome doesn't allow overriding the user agent.
+  // Instead, we send an additional x-user-agent header.
+  return {'X-User-Agent': ua};
+}