.NET out-of-proc error parsing fixes

release_notes.md

@@ -11,6 +11,7 @@
 - Fix issue with isolated entities: custom deserialization was not working because IServices was not passed along (https://github.com/Azure/azure-functions-durable-extension/pull/2686)
 - Fix issue with `string` activity input having extra quotes (https://github.com/Azure/azure-functions-durable-extension/pull/2708)
 - Fix issue with out-of-proc entity operation errors: success/failure details of individual operations in a batch was not processed correctly (https://github.com/Azure/azure-functions-durable-extension/pull/2752)
+- Fix issues with .NET Isolated out-of-process error parsing (see https://github.com/Azure/azure-functions-durable-extension/issues/2711)
 
 ### Breaking Changes
 

src/WebJobs.Extensions.DurableTask/OutOfProcMiddleware.cs

@@ -655,31 +655,48 @@ private static bool TrySplitExceptionTypeFromMessage(
             [NotNullWhen(true)] out string? exceptionType,
             [NotNullWhen(true)] out string? exceptionMessage)
         {
-            // Example exception messages:
+            // In certain situations, like when the .NET Isolated worker is configured with
+            // WorkerOptions.EnableUserCodeException = true, the exception message we get from the .NET Isoalted
+            // worker looks like this:
+            // "Exception of type 'ExceptionSerialization.Function+UnknownException' was thrown."
+            const string startMarker = "Exception of type '";
+            const string endMarker = "' was thrown.";
+            if (exception.StartsWith(startMarker) && exception.EndsWith(endMarker))
+            {
+                exceptionType = exception[startMarker.Length..^endMarker.Length];
+                exceptionMessage = string.Empty;
+                return true;
+            }
+
+            // The following are the more common cases that we expect to see, which will be common across a
+            // variety of language workers:
             // .NET   : System.ApplicationException: Kah-BOOOOM!!
             // Java   : SQLServerException: Invalid column name 'status'.
             // Python : ResourceNotFoundError: The specified blob does not exist. RequestId:8d5a2c9b-b01e-006f-33df-3f7a2e000000 Time:2022-03-25T00:31:24.2003327Z ErrorCode:BlobNotFound Error:None
             // Node   : SyntaxError: Unexpected token N in JSON at position 12768
 
-            // From the above examples, they all follow the same pattern of {ExceptionType}: {Message}
+            // From the above examples, they all follow the same pattern of {ExceptionType}: {Message}.
+            // However, some exception types override the ToString() method and do something custom, in which
+            // case the message may not be in the expected format. In such cases we won't be able to distinguish
+            // the exception type.
             string delimeter = ": ";
             int endExceptionType = exception.IndexOf(delimeter);
             if (endExceptionType < 0)
             {
                 exceptionType = null;
-                exceptionMessage = null;
+                exceptionMessage = exception;
                 return false;
             }
 
-            exceptionType = exception[..endExceptionType];
+            exceptionType = exception[..endExceptionType].TrimEnd();
 
             // The .NET Isolated language worker strangely includes the stack trace in the exception message.
             // To avoid bloating the payload with redundant information, we only consider the first line.
             int startMessage = endExceptionType + delimeter.Length;
             int endMessage = exception.IndexOf('\n', startMessage);
             if (endMessage < 0)
             {
-                exceptionMessage = exception[startMessage..];
+                exceptionMessage = exception[startMessage..].TrimEnd();
             }
             else
             {