For testing this issue:

1. You need to have access to console on your system
2. Curl and python should be installed on your system.
3. Have basic understanding of Json

Test

1. Login as teacher
2. Navigate to Activity examples course
3. Edit "Online Text Assignment" activity
4. Set "Allow submissions from" to more then a year from now.
5. Uncheck "Always show description"
6. Attach few file in description.
7. Edit "Assignment with file submissions"
8. Set "Allow submissions from" to some date in past
9. Uncheck "Always show description"
10. Attach few file in description
11. Edit "Assignment with file submissions"
12. Set "Allow submissions from" to some date in past
13. Check "Always show description"
14. Attach few file in description
15. Run following command on your console (Please remember to replace course id and the token parameters to correct values)

    curl 'http://qa.moodle.net/webservice/rest/server.php?moodlewsrestformat=json' --data 'courseids%5B0%5D=2&wsfunction=mod_assign_get_assignments&wstoken=d49d1fac7125d9fd515c374be8d37c34' | python -m json.tool

16. Confirm you receive a list of courses with four assignments.
17. One of the assignments should not display intro, introattachments and introformat (the one you configured to not display always the description and start date 1 year in future)
18. The other assignments displays description (intro) and a list of attached files (introattachments)