Modify items of an existing checklist

The following example modifies the checklist and shows multiple use cases, it does:

Uncheck all items
Remove the status from items with “In Progress” status
Make the item named “Run all tests” optional

import com.onresolve.scriptrunner.runner.customisers.WithPlugin;
import com.atlassian.jira.component.ComponentAccessor;
import com.atlassian.jira.issue.MutableIssue;
@WithPlugin("com.okapya.jira.checklist")
import com.okapya.jira.customfields.*;

// Retrieve the Custom Field Type for the Checklist Custom Field
def customFieldManager = ComponentAccessor.getCustomFieldManager();
def checklistCustomField = customFieldManager.getCustomFieldObject("customfield_10013");
def checklistCustomFieldType = (ChecklistCFType) checklistCustomField.getCustomFieldType();

// Modify existing items in the Checklist
def issue = (MutableIssue) event.issue;
def ArrayList<ChecklistItem> existingChecklistValue = (ArrayList<ChecklistItem>) issue.getCustomFieldValue(checklistCustomField);
for (ChecklistItem item : existingChecklistValue) {
    // Uncheck all items
    item.setChecked(false);

    // Remove statuses for items "In progress"
    if (item.getStatusId() == "inProgress") {
        item.setStatusId("none");
    }

    // Item "Run all tests" must be optional (not mandatory)
    if (item.getName() == "Run all tests") {
        item.setDiscretionary(true);
    }
}

// Update the issue with the checklist
checklistCustomFieldType.updateValue(checklistCustomField, issue, existingChecklistValue);