The scenario is we create an issue in a project, it gets auto-assigned using the Component settings. Later, we need to move the issue to another project and another Component, but the auto-assignment does not trigger. I also tried with issues that were 'unassigned' but the Component auto-assignment still doesn't trigger on move. But that's not my problem--I've accepted the behavior and moved on 
What I want to know if there is a way I can trigger the behavior via a script. I'm currently working on a Listener in Scriptrunner but I'd rather not recreate the behavior from scratch (are assignments being made by project default, component lead, some other criteria). Is there a function in the Java API that I can call to cause the assignee to be re-evaluated? I know it's a stretch, but I thought I would check before I did too much more work.