reason needs to be exception class name

Signed-off-by: Shijie Sheng <liouvetren@gmail.com>

Author: shijiesheng

cadence/_internal/workflow/workflow_engine.py

@@ -85,10 +85,7 @@ def process_decision(
                         decisions.append(
                             Decision(
                                 fail_workflow_execution_decision_attributes=FailWorkflowExecutionDecisionAttributes(
-                                    failure=Failure(
-                                        reason=str(e),
-                                        details=traceback.format_exc().encode("utf-8"),
-                                    )
+                                    failure=_failure_from_workflow_failure(e)
                                 )
                             )
                         )
@@ -233,3 +230,16 @@ def _extract_workflow_input(
                     return started_attrs.input
 
         raise ValueError("No WorkflowExecutionStarted event found in history")
+
+
+def _failure_from_workflow_failure(e: WorkflowFailure) -> Failure:
+    cause = e.__cause__
+
+    stacktrace = "".join(traceback.format_exception(cause))
+
+    details = f"message: {str(cause)}\nstacktrace: {stacktrace}"
+
+    return Failure(
+        reason=type(cause).__name__,
+        details=details.encode("utf-8"),
+    )

tests/integration_tests/workflow/test_workflows.py

@@ -23,11 +23,15 @@ async def echo(self, message: str) -> str:
         return message
 
 
+class MockedFailure(Exception):
+    pass
+
+
 @reg.workflow()
 class FailureWorkflow:
     @workflow.run
     async def failure(self, message: str) -> str:
-        raise Exception("mocked workflow failure")
+        raise MockedFailure("mocked workflow failure")
 
 
 async def test_simple_workflow(helper: CadenceHelper):
@@ -77,14 +81,14 @@ async def test_workflow_failure(helper: CadenceHelper):
         )
 
         assert (
-            "Workflow failed: mocked workflow failure"
+            "MockedFailure"
             == response.history.events[
                 -1
             ].workflow_execution_failed_event_attributes.failure.reason
         )
 
         assert (
-            """raise Exception("mocked workflow failure")"""
+            """raise MockedFailure("mocked workflow failure")"""
             in response.history.events[
                 -1
             ].workflow_execution_failed_event_attributes.failure.details.decode()