CHANGELOG.md

@@ -1,3 +1,8 @@
+## 4.1.2-dev
+
+- Send `fetch` requests instead of `XHR` requests.
+- Add an optional `debugKey` parameter to `SseClient` to include in logging.
+
 ## 4.1.1
 
 - Apply `keepAlive` logic to `SocketException`s.
@@ -25,8 +30,8 @@
 
 ## 3.8.1
 
-- Fix an issue where closing the `SseConnection` stream would result in
-  an error.
+- Fix an issue where closing the `SseConnection` stream would result in an
+  error.
 
 ## 3.8.0
 
@@ -36,8 +41,8 @@
 
 ## 3.7.0
 
-- Deprecate the client's `onOpen` getter. Messages will now be buffered until
-  a connection is established.
+- Deprecate the client's `onOpen` getter. Messages will now be buffered until a
+  connection is established.
 
 ## 3.6.1
 
@@ -48,15 +53,14 @@
 - Improve performance by buffering out of order messages in the server instead
   of the client.
 
-** Note ** This is not modelled as a breaking change as the server can handle
-messages from older clients. However, clients should be using the latest server
-if they require order guarantees.
-
+\*\* Note \*\* This is not modelled as a breaking change as the server can
+handle messages from older clients. However, clients should be using the latest
+server if they require order guarantees.
 
 ## 3.5.0
 
-- Add new `shutdown` methods on `SseHandler` and `SseConnection` to allow closing
-  connections immediately, ignoring any keep-alive periods.
+- Add new `shutdown` methods on `SseHandler` and `SseConnection` to allow
+  closing connections immediately, ignoring any keep-alive periods.
 
 ## 3.4.0
 
@@ -65,14 +69,14 @@ if they require order guarantees.
 
 ## 3.3.0
 
-- Add an `onClose` event to the `SseConnection`. This allows consumers to
-  listen to this event in lue of `sseConnection.sink.done` as that is not
-  guaranteed to fire.
+- Add an `onClose` event to the `SseConnection`. This allows consumers to listen
+  to this event in lue of `sseConnection.sink.done` as that is not guaranteed to
+  fire.
 
 ## 3.2.2
 
-- Fix an issue where `keepAlive` may cause state errors when attempting to
-  send messages on a closed stream.
+- Fix an issue where `keepAlive` may cause state errors when attempting to send
+  messages on a closed stream.
 
 ## 3.2.1
 
@@ -94,21 +98,21 @@ if they require order guarantees.
 - Make `isInKeepAlive` on `SseConnection` private.
 
 **Note that this is a breaking change but in actuality no one should be
-  depending on this API.**
+depending on this API.**
 
 ## 3.1.0
 
 - Add optional `keepAlive` parameter to the `SseHandler`. If `keepAlive` is
-  supplied, the connection will remain active for this period after a
-  disconnect and can be reconnected transparently. If there is no reconnect
-  within that period, the connection will be closed normally.
+  supplied, the connection will remain active for this period after a disconnect
+  and can be reconnected transparently. If there is no reconnect within that
+  period, the connection will be closed normally.
 
 ## 3.0.0
 
 - Add retry logic.
 
-**Possible Breaking Change Error messages may now be delayed up to 5 seconds
-  in the client.**
+**Possible Breaking Change Error messages may now be delayed up to 5 seconds in
+the client.**
 
 ## 2.1.2
 
@@ -145,7 +149,6 @@ if they require order guarantees.
 
 - Internal cleanup.
 
-
 ## 0.0.1
 
 - Initial commit.

CONTRIBUTING.md

@@ -2,6 +2,7 @@ Want to contribute? Great! First, read this page (including the small print at
 the end).
 
 ### Before you contribute
+
 Before we can use your code, you must sign the
 [Google Individual Contributor License Agreement](https://cla.developers.google.com/about/google-individual)
 (CLA), which you can do online. The CLA is necessary mainly because you own the
@@ -18,16 +19,21 @@ possibly guide you. Coordinating up front makes it much easier to avoid
 frustration later on.
 
 ### Code reviews
+
 All submissions, including submissions by project members, require review.
 
 ### File headers
+
 All files in the project must start with the following header.
 
-    // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
-    // for details. All rights reserved. Use of this source code is governed by a
-    // BSD-style license that can be found in the LICENSE file.
+```
+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+```
 
 ### The small print
+
 Contributions made by corporations are covered by a different agreement than the
 one above, the
 [Software Grant and Corporate Contributor License Agreement](https://developers.google.com/open-source/cla/corporate).

README.md

@@ -2,13 +2,13 @@
 [![pub package](https://img.shields.io/pub/v/sse.svg)](https://pub.dev/packages/sse)
 [![package publisher](https://img.shields.io/pub/publisher/sse.svg)](https://pub.dev/packages/sse/publisher)
 
-This package provides support for bi-directional communication through
-Server Sent Events and corresponding POST requests.
+This package provides support for bi-directional communication through Server
+Sent Events and corresponding POST requests.
 
-This package is not intended to be a general purpose SSE package, but instead
-is a bidirectional protocol for use when Websockets are unavailable.
-That is, both the client and the server expose a `sink` and `stream` on which to send
-and receive messages respectively.
+This package is not intended to be a general purpose SSE package, but instead is
+a bidirectional protocol for use when Websockets are unavailable. That is, both
+the client and the server expose a `sink` and `stream` on which to send and
+receive messages respectively.
 
-Both the server and client have implicit assumptions on each other and therefore a
-client from this package must be paired with a server from this package.
+Both the server and client have implicit assumptions on each other and therefore
+a client from this package must be paired with a server from this package.

lib/client/sse_client.dart

@@ -6,6 +6,7 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:html';
 
+import 'package:js/js.dart';
 import 'package:logging/logging.dart';
 import 'package:pool/pool.dart';
 import 'package:stream_channel/stream_channel.dart';
@@ -25,6 +26,8 @@ final _requestPool = Pool(1000);
 /// The client can send any JSON-encodable messages to the server by adding
 /// them to the [sink] and listen to messages from the server on the [stream].
 class SseClient extends StreamChannelMixin<String?> {
+  final String _clientId;
+
   final _incomingController = StreamController<String>();
 
   final _outgoingController = StreamController<String>();
@@ -42,12 +45,14 @@ class SseClient extends StreamChannelMixin<String?> {
   Timer? _errorTimer;
 
   /// [serverUrl] is the URL under which the server is listening for
-  /// incoming bi-directional SSE connections.
-  SseClient(String serverUrl) {
-    var clientId = generateUuidV4();
-    _eventSource =
-        EventSource('$serverUrl?sseClientId=$clientId', withCredentials: true);
-    _serverUrl = '$serverUrl?sseClientId=$clientId';
+  /// incoming bi-directional SSE connections. [debugKey] is an optional key
+  /// that can be used to identify the SSE connection.
+  SseClient(String serverUrl, {String? debugKey})
+      : _clientId = debugKey == null
+            ? generateUuidV4()
+            : '$debugKey-${generateUuidV4()}' {
+    _serverUrl = '$serverUrl?sseClientId=$_clientId';
+    _eventSource = EventSource(_serverUrl, withCredentials: true);
     _eventSource.onOpen.first.whenComplete(() {
       _onConnected.complete();
       _outgoingController.stream
@@ -64,13 +69,7 @@ class SseClient extends StreamChannelMixin<String?> {
         // By default the SSE client uses keep-alive.
         // Allow for a retry to connect before giving up.
         _errorTimer = Timer(const Duration(seconds: 5), () {
-          _incomingController.addError(error);
-          close();
-          if (!_onConnected.isCompleted) {
-            // This call must happen after the call to close() which checks
-            // whether the completer was completed earlier.
-            _onConnected.completeError(error);
-          }
+          _closeWithError(error);
         });
       }
     });
@@ -103,12 +102,22 @@ class SseClient extends StreamChannelMixin<String?> {
     _outgoingController.close();
   }
 
+  void _closeWithError(Object error) {
+    _incomingController.addError(error);
+    close();
+    if (!_onConnected.isCompleted) {
+      // This call must happen after the call to close() which checks
+      // whether the completer was completed earlier.
+      _onConnected.completeError(error);
+    }
+  }
+
   void _onIncomingControlMessage(Event message) {
     var data = (message as MessageEvent).data;
     if (data == 'close') {
       close();
     } else {
-      throw UnsupportedError('Illegal Control Message "$data"');
+      throw UnsupportedError('[$_clientId] Illegal Control Message "$data"');
     }
   }
 
@@ -128,17 +137,51 @@ class SseClient extends StreamChannelMixin<String?> {
       try {
         encodedMessage = jsonEncode(message);
       } on JsonUnsupportedObjectError catch (e) {
-        _logger.warning('Unable to encode outgoing message: $e');
+        _logger.warning('[$_clientId] Unable to encode outgoing message: $e');
       } on ArgumentError catch (e) {
-        _logger.warning('Invalid argument: $e');
+        _logger.warning('[$_clientId] Invalid argument: $e');
       }
       try {
-        await HttpRequest.request('$_serverUrl&messageId=${++_lastMessageId}',
-            method: 'POST', sendData: encodedMessage, withCredentials: true);
-      } catch (e) {
-        _logger.severe('Failed to send $message:\n $e');
-        close();
+        final url = '$_serverUrl&messageId=${++_lastMessageId}';
+        await _fetch(
+            url,
+            _FetchOptions(
+                method: 'POST',
+                body: encodedMessage,
+                credentialsOptions:
+                    _CredentialsOptions(credentials: 'include')));
+      } catch (error) {
+        final augmentedError =
+            '[$_clientId] SSE client failed to send $message:\n $error';
+        _logger.severe(augmentedError);
+        _closeWithError(augmentedError);
       }
     });
   }
 }
+
+// Custom implementation of Fetch API until Dart supports GET vs. POST,
+// credentials, etc. See https://github.com/dart-lang/http/issues/595.
+@JS('fetch')
+external Object _nativeJsFetch(String resourceUrl, _FetchOptions options);
+
+Future<dynamic> _fetch(String resourceUrl, _FetchOptions options) =>
+    promiseToFuture(_nativeJsFetch(resourceUrl, options));
+
+@JS()
+@anonymous
+class _FetchOptions {
+  external factory _FetchOptions({
+    required String method, // e.g., 'GET', 'POST'
+    required _CredentialsOptions credentialsOptions,
+    required String? body,
+  });
+}
+
+@JS()
+@anonymous
+class _CredentialsOptions {
+  external factory _CredentialsOptions({
+    required String credentials, // e.g., 'omit', 'same-origin', 'include'
+  });
+}

lib/src/server/sse_handler.dart

@@ -264,14 +264,15 @@ class SseHandler {
 
   Future<shelf.Response> _handleIncomingMessage(
       shelf.Request req, String path) async {
+    String? clientId;
     try {
-      var clientId = req.url.queryParameters['sseClientId'];
+      clientId = req.url.queryParameters['sseClientId'];
       var messageId = int.parse(req.url.queryParameters['messageId'] ?? '0');
       var message = await req.readAsString();
       var jsonObject = json.decode(message) as String;
       _connections[clientId]?._addIncomingMessage(messageId, jsonObject);
     } catch (e, st) {
-      _logger.fine('Failed to handle incoming message. $e $st');
+      _logger.fine('[$clientId] Failed to handle incoming message. $e $st');
     }
     return shelf.Response.ok('', headers: {
       'access-control-allow-credentials': 'true',

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sse
-version: 4.1.1
+version: 4.1.2-dev
 description: >-
   Provides client and server functionality for setting up bi-directional
   communication through Server Sent Events (SSE) and corresponding POST