fix(http2): make StreamException a StreamTransportException and forward ALPN errors to onError

pkgs/http2/CHANGELOG.md

@@ -23,6 +23,10 @@
   stream when a stream is cancelled; drop the stream's queued `DATA` instead.
 - Stop head-of-line blocking `HEADERS`, `RST_STREAM`, and `GOAWAY` behind
   `DATA` that is waiting for connection-level flow-control credit.
+- `StreamException` (a stream reset because of a `GOAWAY` or oversized headers)
+  now extends `StreamTransportException`, as documented for `TransportException`
+  subclasses. `MultiProtocolHttpServer.startServing` forwards an unexpected ALPN
+  protocol to `onError` instead of throwing inside the socket listener.
 
 ## 3.1.0
 

pkgs/http2/lib/multiprotocol_server.dart

@@ -91,7 +91,14 @@ class MultiProtocolHttpServer {
         );
       } else {
         socket.destroy();
-        throw Exception('Unexpected negotiated ALPN protocol: $protocol.');
+        final error = Exception(
+          'Unexpected negotiated ALPN protocol: $protocol.',
+        );
+        if (onError != null) {
+          onError(error, StackTrace.current);
+        } else {
+          throw error;
+        }
       }
     }, onError: onError);
 

pkgs/http2/lib/src/sync_errors.dart

@@ -2,6 +2,8 @@
 // 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.
 
+import '../transport.dart';
+
 class ProtocolException implements Exception {
   final String _message;
 
@@ -44,27 +46,29 @@ class TerminatedException implements Exception {
   String toString() => 'TerminatedException: The object has been terminated.';
 }
 
-class StreamException implements Exception {
-  final String _message;
+class StreamException extends StreamTransportException {
   final int streamId;
+  final String _details;
 
-  StreamException(this.streamId, this._message);
+  StreamException(this.streamId, String details)
+    : _details = details,
+      super(details);
 
   @override
-  String toString() => 'StreamException(stream id: $streamId): $_message';
+  String toString() => 'StreamException(stream id: $streamId): $_details';
 }
 
 class StreamClosedException extends StreamException {
-  StreamClosedException(super.streamId, [super.message = '']);
+  StreamClosedException(super.streamId, [super.details = '']);
 
   @override
-  String toString() => 'StreamClosedException(stream id: $streamId): $_message';
+  String toString() => 'StreamClosedException(stream id: $streamId): $_details';
 }
 
 class StreamRefusedException extends StreamException {
-  StreamRefusedException(super.streamId, [super.message = '']);
+  StreamRefusedException(super.streamId, [super.details = '']);
 
   @override
   String toString() =>
-      'StreamRefusedException(stream id: $streamId): $_message';
+      'StreamRefusedException(stream id: $streamId): $_details';
 }

pkgs/http2/test/client_test.dart

@@ -1321,7 +1321,8 @@ void main() {
           // Make sure we don't get messages/pushes on the terminated stream.
           unawaited(
             stream.incomingMessages.toList().catchError(
-              expectAsync1((e) {
+              expectAsync1((Object e) {
+                expect(e, isA<StreamTransportException>());
                 expect(
                   '$e',
                   contains(