Scratch.groovy

package examples

import com.atlassian.jira.bc.issue.IssueService
import com.atlassian.jira.component.ComponentAccessor
import com.atlassian.jira.event.issue.IssueEvent
import com.atlassian.jira.event.type.EventDispatchOption

IssueEvent event = event

def issue = event.issue
if (! event.getChangeLog()?.getRelated("ChildChangeItem")?.any { it.get('field') == "summary"}) {
    return
}

def user = ComponentAccessor.getJiraAuthenticationContext().getLoggedInUser()
def issueService = ComponentAccessor.issueService

issue.subTaskObjects.each { subtask ->
    def issueInputParameters = issueService.newIssueInputParameters()
    issueInputParameters.setSummary(issue.summary)
    IssueService.UpdateValidationResult updateValidationResult = issueService.validateUpdate(user, subtask.id, issueInputParameters)

    if (updateValidationResult.isValid()) {
        IssueService.IssueResult updateResult = issueService.update(user, updateValidationResult, EventDispatchOption.ISSUE_UPDATED, false)
        if (updateResult.isValid()) {
            log.debug 'Issue updated: '
        } else {
            log.error "Error updating subtask: ${subtask.key} - ${updateResult.getErrorCollection()}"
        }
    } else {
        log.error 'Error validating update' + updateValidationResult.getErrorCollection()
    }
}