Fix side effect determinism check during replay

#116

Author: cschleiden

internal/command/sideeffect.go

@@ -14,16 +14,19 @@ type SideEffectCommand struct {
 
 var _ Command = (*SideEffectCommand)(nil)
 
-func NewSideEffectCommand(id int64, result payload.Payload) *SideEffectCommand {
+func NewSideEffectCommand(id int64) *SideEffectCommand {
 	return &SideEffectCommand{
 		command: command{
 			state: CommandState_Pending,
 			id:    id,
 		},
-		result: result,
 	}
 }
 
+func (c *SideEffectCommand) SetResult(result payload.Payload) {
+	c.result = result
+}
+
 func (c *SideEffectCommand) Type() string {
 	return "SideEffect"
 }

workflow/sideeffect.go

@@ -22,26 +22,23 @@ func SideEffect[TResult any](ctx Context, f func(ctx Context) TResult) Future[TR
 	wfState := workflowstate.WorkflowState(ctx)
 	scheduleEventID := wfState.GetNextScheduleEventID()
 
-	if Replaying(ctx) {
-		// There has to be a message in the history with the result, create a new future
-		// and block on it
-		wfState.TrackFuture(scheduleEventID, workflowstate.AsDecodingSettable(future))
-		return future
-	}
+	wfState.TrackFuture(scheduleEventID, workflowstate.AsDecodingSettable(future))
 
-	// Execute side effect
-	r := f(ctx)
+	cmd := command.NewSideEffectCommand(scheduleEventID)
+	wfState.AddCommand(cmd)
 
-	// Create command to add it to the history
-	payload, err := converter.DefaultConverter.To(r)
-	if err != nil {
-		future.Set(*new(TResult), err)
-	}
+	if !Replaying(ctx) {
+		// Execute side effect
+		r := f(ctx)
 
-	cmd := command.NewSideEffectCommand(scheduleEventID, payload)
-	wfState.AddCommand(cmd)
+		payload, err := converter.DefaultConverter.To(r)
+		if err != nil {
+			future.Set(*new(TResult), err)
+		}
 
-	future.Set(r, nil)
+		cmd.SetResult(payload)
+		future.Set(r, nil)
+	}
 
 	return future
 }