Description:

Searches subtasks of standard issues which satisfies the provided subquery.
See also: parentsOf()

Note:
Since you need to enclose the provided subquery using doble quotes, you must to escape any doble quotes using in the subquery by preceding a backslash after the double quotes, alternatively you can use a single quote in some cases.

Let's see an example...

This will not work

issue IN subtasksOf("resolution = "Won't Do" AND status = Closed")

^{Searches for all subtasks of closed issues which their resolution have been set to "Won't Do"}

This will work perfectly

issue IN subtasksOf("resolution = \"Won't Do\" AND status = Closed")

^{Searches for all subtasks of closed issues which their resolution have been set to "Won't Do"}

issue IN subtasksOf("status = 'In Progress' AND reporter = currentUser()")

^{Searches for all subtasks of in proress issues reporter by me}

Syntax	subtasksOf(subquery)
Available since	v1.2.0-RELEASE
Supported fields	Issue
Supported operators	`IN , NOT IN`
Unsupported operators	`=` `,` `!=` `,` `~` `,` `!~` `,` `>` `,` `>=` `,` `<` `,` `<=` `IS` `,` `IS NOT` `,` `WAS` `,` `WAS IN` `,` `WAS NOT` `,` `WAS NOT IN` `,` `CHANGED`

Examples:

• Find subtasks of 'Open' issues:

issue IN subtasksOf("status = Open")

• Find 'Unresolved' subtasks of 'Closed' issues which their resolution have been set to 'Won't Do'

issue IN subtasksOf("resolution = \"Won't Do\" AND status = Closed") AND resolution = Unresolved

• Find 'In Progress' subtasks of 'Bug' issues created in 'LATAM' project:

issue IN subtasksOf("issuetype = Bug AND project = LATAM") AND status = "In Progress"

Real World Use Cases:

· JQL to show all issues AND subtasks in the Epic (by Nathan at ATLASSIAN Community).
· Jira Filter with "parent in" (by Hansi at ATLASSIAN Community).
· JRASERVER-18839 - Create a JQL funcionality to filter the sub-task for a field value of the parent issue (by Abner Luis Santos Rolim)
· How to get subtasks of an EPIC in a filter query? (by Paulo Costa)

JQL Function Reference