When you add this post-function to a transition, the add-on executes the provided Groovy script against the current issue. This post-function can be used in scenarios where you want to act on the current issue or on related issues in ways that are not supported by other JMWE post-functions. For example, you might want to copy attachments of the current issue to its linked issues, which is not currently supported by the Copy field value to related issues post-function.
By default, all errors (Java Exceptions) raised by this post-function, including those raised by custom Groovy scripts, will be logged in the JIRA log file but will not be reported to the user and will not prevent the transition from completing. However, when designing new workflows or troubleshooting them, it is more convenient to be notified immediately of any such error during the execution of the transition. For example on the production Jira instances you might want to show errors only for the post-function(s) being worked on, in order to avoid disrupting other workflows. To make errors raised by the current post-function prevent the transition from completing and show the error in the browser, select Make transition fail when an error occurs in this post-function.
If you want to show all the errors, either only to the admins or to all users, configure the option globally on the JMWE configuration page. For example, on development and staging Jira instances, you can activate error reporting for all JMWE post-functions, to display all the errors and it is recommended to do so, and on production Jira instances you might want to activate error reporting only to administrators so that they can be made aware of configuration errors.