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import com.atlassian.jira.component.ComponentAccessor
import org.apache.log4j.Category
import com.atlassian.jira.issue.MutableIssue
 
/**
 * The template script for setting the assignee from a custom user picker
 * Make sure the user chosen is assignable.
 */
 
def Category log = Category.getInstance("com.onresolve.jira.groovy.PostFunction");
log.setLevel(org.apache.log4j.Level.DEBUG);
  
def issueManager = ComponentAccessor.getIssueManager();
def customFieldManager = componentManager.getCustomFieldManager();
def cf = customFieldManager.getCustomFieldObjectByName("Source User");
if (cf == null) {
    log.error("No custom field found");
    return;
}
def user = issue.getCustomFieldValue(cf);
if (user != null) {
    def user2 = user.getDirectoryUser();
    log.error("Setting assignee to: " + user2.getName());
    log.error("Issue type : " + issue.getClass().getName());
    MutableIssue mutableIssue = issueManager.getIssueObject(issue.id)
    mutableIssue.setAssignee(user2);
    mutableIssue.store();
}