Looking to clear Assignee field on a transition back to initial status, IF task has reached a 'final' state

[Deleted user]

In some workflows within our JIRA Core (cloud) instance, I have a transition that is available to ALL steps which will send the task back to its initial status of "Pending".  

I would like to clear the Assignee field when that transition is selected IF the task is in a FINAL status (e.g., status = Done).  

Can this be accomplished using built-in JIRA transition operations (Condition, Validator, Post)?  If so, can someone give a suggestion on accomplishing it.

To summarize:

-Our initial status is called "Pending", all statuses can transition back to it.  That transition is named “Initiate Amendment”

-Interested in clearing the built-in “Assignee” field, WHEN the "Initiate Amendment" transition is selected IF the sub-task has reached a "Done" status

Thanks in advance!

[Jon Bevan _Adaptavist_]

Hi Stephen,

You can use ScriptRunner for JIRA Cloud to achieve this. You can create a workflow post function on the transition you mentioned with a condition to check which status you're transitioning from, and then remove the assignee in the main code for the transition:

// The condition
(transitionInput.transition as Map).from_status == 'Done'

and...

// Update the issue, removing the assignee
def resp = put("/rest/api/2/issue/${issue.key}") 
    .header("Content-Type", "application/json")
    .body([
        fields:[
                'assignee': null
        ]
    ])
    .asString()
assert resp.status == 204

Here's a screenshot too https://drive.google.com/file/d/0B6nyDigBko1ldTR3c1FrQk50X0E/view?usp=sharing

Let me know if you need more help (or if I've left some bugs in the code above!),

Jon

[Deleted user]

Thanks, Jon.  I'm going to try it out shortly!