In certain cases, the call behavior or call operation action generated for an invocation expression is wrapped in a structured activity node with an output pin for the call action result. This is done so that a null token is offered even if the call action does not fire due to missing optional inputs. However, since the structured activity node has no incoming control flow, but the call action does (from its tuple mapping), it is actually possible for the structured activity node to fire before the call action is ready, meaning that a null token is generated incorrectly as the result of the invocation expression. This can be prevented by add a control flow from the tuple mapping to the structured activity node.
seidewitz
commented
6 years ago
In certain cases, the call behavior or call operation action generated for an invocation expression is wrapped in a structured activity node with an output pin for the call action result. This is done so that a null token is offered even if the call action does not fire due to missing optional inputs. However, since the structured activity node has no incoming control flow, but the call action does (from its tuple mapping), it is actually possible for the structured activity node to fire before the call action is ready, meaning that a null token is generated incorrectly as the result of the invocation expression. This can be prevented by add a control flow from the tuple mapping to the structured activity node.