Can I override "Allow Unassigned Issues - Off" in System Settings using a Post Function?

[Marty Williams]

With so many Project Spaces in JIRA, and many hundreds of users, I don't want to enable Allow Unassigned Issues.  

I want to be able to assign certain issues to the %REPORTER% on issue create, and not the project lead.

[Nic Brough -Adaptavist-]

There's two parts to this

1.  If you want unassigned issues in some places and not others, that's possible - in the project/issuetypes you want the assignee to be filled at all times, use the field configuration to make the assignee mandatory
2. JIRA doesn't support this in the "automatic" options (you can do unassigned, project lead or component lead), but if you always want to set it, you can use the "update field" post-function to set it.  If you want it to be conditional (i.e. "if user leaves it blank, set it to reporter") then you'll need a spot of code to do the post-function