bring back lastDecisionEventsForReplayTest because it's needed for partial decisions

Author: taylanisikdemir

internal/internal_task_handlers.go

@@ -979,7 +979,11 @@ ProcessEvents:
 			}
 		}
 		isReplay := len(reorderedEvents) > 0 && reorderedHistory.IsReplayEvent(reorderedEvents[len(reorderedEvents)-1])
-		if isReplay {
+		// incomplete decisions (e.g. start without a complete) at the end of history will still have decisions in decisionsHelper
+		// but there won't be corresponding respond events. This breaks the non-determinism check therefore we ignore such final partial decisions.
+		// Example scenario is covered by TestReplayWorkflowHistory_Partial_NoDecisionEvents
+		lastDecisionEventsForReplayTest := isReplayTest && !reorderedHistory.HasNextDecisionEvents()
+		if isReplay && !lastDecisionEventsForReplayTest {
 			eventDecisions := eventHandler.decisionsHelper.getDecisions(true)
 			if len(eventDecisions) > 0 && !skipReplayCheck {
 				replayDecisions = append(replayDecisions, eventDecisions...)

internal/workflow_replayer_test.go

@@ -99,6 +99,23 @@ func (s *workflowReplayerSuite) TestReplayWorkflowHistory_Partial_WithDecisionEv
 	s.NoError(err)
 }
 
+// This test case covers partial decision scenario where a decision is started but not closed
+// History:
+//
+//	1: WorkflowExecutionStarted
+//	2: DecisionTaskScheduled
+//	3: DecisionTaskStarted
+//	4: DecisionTaskFailed
+//	5: DecisionTaskScheduled
+//	6: DecisionTaskStarted
+//
+// Notes on task handling logic during replay:
+//
+//	reorderedHistory.NextDecisionEvents() ignores events 2, 3, 4 because it failed.
+//	it only returns 1 and 6 to be replayed.
+//	6 changes the state in decisionsHelper (generates a decision) however there's no corresponding
+//	respond due to missing close event (failed/complete etc.)
+//	Such partial decisions at the end of the history is ignored during replay tests to avoid non-determinism error
 func (s *workflowReplayerSuite) TestReplayWorkflowHistory_Partial_NoDecisionEvents() {
 	err := s.replayer.ReplayWorkflowHistory(s.logger, getTestReplayWorkflowPartialHistoryNoDecisionEvents(s.T()))
 	s.NoError(err)