Adds initial Reporter as a Participant, and sets the user in custom field "Primary User" as the new Reporter. For use in JIRA Service Desk.

addReporterAsParticipant.groovy

import com.atlassian.jira.component.ComponentAccessor
import com.atlassian.jira.event.type.EventDispatchOption
import com.atlassian.jira.issue.CustomFieldManager
import com.atlassian.jira.issue.MutableIssue
import com.atlassian.jira.issue.IssueManager
import java.util.ArrayList
import com.atlassian.jira.user.ApplicationUser
import org.apache.log4j.Logger
def log = Logger.getLogger("com.acme.XXX")

def currentUser = ComponentAccessor.getJiraAuthenticationContext().getLoggedInUser()
def REQUEST_PARTICIPANTS_FIELD = "customfield_10600"
def PRIMARY_USER_FIELD = "customfield_10913"

CustomFieldManager customFieldManager = ComponentAccessor.getCustomFieldManager()
IssueManager issueManager = ComponentAccessor.getIssueManager()

MutableIssue myIssue = issue

// For testing in the Script Console, hard-code an issue object.
// MutableIssue myIssue = issueManager.getIssueObject("ATW-37")

// Get custom field objects.
def requestParticipantsField = customFieldManager.getCustomFieldObject(REQUEST_PARTICIPANTS_FIELD)
def primaryUserField = customFieldManager.getCustomFieldObject(PRIMARY_USER_FIELD)

// Get initial Reporter.
ApplicationUser reporter = myIssue.getReporter()

// Add initial Reporter to array.
ArrayList<ApplicationUser> participants = []
participants.add(reporter)

// Get initial Primary User.
ApplicationUser primaryUser = myIssue.getCustomFieldValue(primaryUserField) as ApplicationUser

if (primaryUser) {
	// Update the Request Participants field.
	myIssue.setCustomFieldValue(
	    requestParticipantsField, 
	    participants
	)

	// Update the Reporter field.
	myIssue.setReporter(primaryUser)

	// Clear the Primary User field.
	myIssue.setCustomFieldValue(
        primaryUserField,
        null
    )

	// Store to database.
	try {
		issueManager.updateIssue(
			currentUser,
			myIssue,
			EventDispatchOption.ISSUE_UPDATED,
			false
		)
	} catch (Exception e) {
		log.debug "Exception: " + e
	}
} else {
	log.debug "No Primary User specified."
}