session: fix exception handling in microtask

example/in_memory_router.dart

@@ -1,5 +1,3 @@
-import "package:wampproto/serializers.dart";
-
 import "package:xconn/exports.dart";
 import "package:xconn/src/types.dart";
 

lib/exports.dart

@@ -3,6 +3,7 @@ export "package:wampproto/auth.dart"
 export "package:wampproto/serializers.dart" show CBORSerializer, JSONSerializer, MsgPackSerializer, Serializer;
 
 export "src/client.dart" show Client;
+export "src/exception.dart" show ApplicationError, ProtocolError;
 export "src/router.dart" show Router;
 export "src/server.dart" show Server;
 export "src/session.dart" show Session;

lib/src/exception.dart

@@ -0,0 +1,27 @@
+class ApplicationError implements Exception {
+  ApplicationError(this.message, {this.args, this.kwargs});
+
+  final String message;
+  final List<dynamic>? args;
+  final Map<String, dynamic>? kwargs;
+
+  @override
+  String toString() {
+    String errStr = message;
+    if (args?.isNotEmpty ?? false) {
+      String argsStr = args!.map((arg) => arg.toString()).join(", ");
+      errStr += ": $argsStr";
+    }
+    if (kwargs?.isNotEmpty ?? false) {
+      String kwargsStr = kwargs!.entries.map((entry) => "${entry.key}=${entry.value}").join(", ");
+      errStr += ": $kwargsStr";
+    }
+    return errStr;
+  }
+}
+
+class ProtocolError implements Exception {
+  ProtocolError(this.message);
+
+  final String message;
+}

lib/src/session.dart

@@ -3,6 +3,7 @@ import "dart:async";
 import "package:wampproto/idgen.dart";
 import "package:wampproto/messages.dart" as msg;
 import "package:wampproto/session.dart";
+import "package:xconn/src/exception.dart";
 
 import "package:xconn/src/helpers.dart";
 import "package:xconn/src/types.dart";
@@ -90,30 +91,52 @@ class Session {
     } else if (message is msg.Error) {
       switch (message.msgType) {
         case msg.Call.id:
-          _callRequests.remove(message.requestID);
+          var callRequest = _callRequests.remove(message.requestID);
+          callRequest?.completeError(
+            ApplicationError(message.uri, args: message.args, kwargs: message.kwargs),
+          );
           break;
 
         case msg.Register.id:
-          _registerRequests.remove(message.requestID);
+          var registerRequest = _registerRequests.remove(message.requestID);
+          registerRequest?.future.completeError(
+            ApplicationError(message.uri, args: message.args, kwargs: message.kwargs),
+          );
           break;
 
         case msg.UnRegister.id:
-          _unregisterRequests.remove(message.requestID);
+          var unregisterRequest = _unregisterRequests.remove(message.requestID);
+          unregisterRequest?.future.completeError(
+            ApplicationError(message.uri, args: message.args, kwargs: message.kwargs),
+          );
           break;
 
         case msg.Subscribe.id:
-          _subscribeRequests.remove(message.requestID);
+          var subscribeRequest = _subscribeRequests.remove(message.requestID);
+          subscribeRequest?.future.completeError(
+            ApplicationError(message.uri, args: message.args, kwargs: message.kwargs),
+          );
           break;
 
         case msg.UnSubscribe.id:
-          _unsubscribeRequests.remove(message.requestID);
+          var unsubscribeRequest = _unsubscribeRequests.remove(message.requestID);
+          unsubscribeRequest?.future.completeError(
+            ApplicationError(message.uri, args: message.args, kwargs: message.kwargs),
+          );
           break;
 
         case msg.Publish.id:
-          _publishRequests.remove(message.requestID);
-      }
+          var publishRequest = _publishRequests.remove(message.requestID);
+          publishRequest?.completeError(
+            ApplicationError(message.uri, args: message.args, kwargs: message.kwargs),
+          );
+          break;
 
-      throw Exception(wampErrorString(message));
+        default:
+          throw ProtocolError(wampErrorString(message));
+      }
+    } else {
+      throw ProtocolError("Unexpected message type ${message.runtimeType}");
     }
   }
 

test/router_test.dart

@@ -1,6 +1,5 @@
 import "package:test/test.dart";
 import "package:wampproto/messages.dart" as msg;
-import "package:wampproto/serializers.dart";
 
 import "package:xconn/exports.dart";
 import "package:xconn/src/types.dart";