This script works only to check for the attachments that are already present for the current issue. If you need to check for attachments that are being added in the transition screen, please use !hasInput("attachments") instead of size(attachments) == 0.
See also
- Disabling inline edits in Jira
- Forbidding users to create some issue types
- Hide fields from users not in a project role
- Limit Number of Characters in Text Field
- Lock an issue - a better variant (Live Fields)
- Locking Issues
- Making an issue read-only
- Require User to Log Work Before Transitioning Issue
- Restrict issue type availability by user
- Restrict workflow based on status of dependencies
- Validator for component lead