How to popup Wen Item Dialog in script runner post function

[saroja muninaga]

I need to popup a dialog window if some custom condition fails in script runner post function in jira  

[Nic Brough -Adaptavist-]

You cannot do this - post-functions have no connection to the front end.  If you need to give data to the user after a transition, you need to write it back on to the issue.

It would be better to use a validator that will prevent the transition if the condition is not met.