NullPointerException when trying to map non-existent group in Notification Scheme to project role using Group to Project Role Mapping Tool

Symptoms

Stack trace (from 500 page):

2010-02-03 17:12:19,980 http-8080-Processor23 [webwork.dispatcher.ServletDispatcher] Could not execute action
java.lang.NullPointerException
at com.atlassian.jira.scheme.mapper.SchemeTransformResult.addRoleMappingForGroup(SchemeTransformResult.java:126)
at com.atlassian.jira.scheme.mapper.SchemeGroupsToRolesTransformerImpl.transformScheme(SchemeGroupsToRolesTransformerImpl.java:172)
at com.atlassian.jira.scheme.mapper.SchemeGroupsToRolesTransformerImpl.doTransform(SchemeGroupsToRolesTransformerImpl.java:48)
at com.atlassian.jira.bc.scheme.mapper.DefaultSchemeGroupsToRoleTransformerService.doTransform(DefaultSchemeGroupsToRoleTransformerService.java:41)
at com.atlassian.jira.web.action.admin.scheme.mapper.SchemeGroupToRoleTransformerAction.doDefault(SchemeGroupToRoleTransformerAction.java:50)

Steps to reproduce

1. Create a group testgroup
2. Add group to an event in Default Notification Scheme
3. Delete group testgroup
4. Go to Administration > Scheme Tools > Group to Project Role Mapping Tool
5. From the dropdown select notification scheme and then from the list select Default Notification Scheme and then click Map Groups to Roles
6. Next to the group testgroup select the dropdown Users and click Preview Mappings
7. 500 page with exception is shown

I guess this is a bug in two ways:

• NullPointerException shouldn't be thrown. There should be some way of mapping out the non-existent group to a project role.
• But more importantly, when you delete a group, it should delete associated scheme entities

We should at least have a check for this in the Integrity Checker?

Workaround

As a workaround for this bug, we can remove the groups that no longer exists from the Notification schemes and Permission Schemes.

We can find what schemes have non-existant groups by running the following queries on your database

Notification Schemes:

select NS.name,N.notif_parameter
from notification N
join notificationscheme NS on N.scheme=NS.id
where N.notif_type = 'Group_Dropdown'
  and N.notif_parameter not in (select group_name from cwd_group)
group by NS.name,N.notif_parameter

Permission Schemes:

select PS.name,P.perm_parameter
from schemepermissions P
join permissionscheme PS on P.scheme=PS.id
where P.perm_type = 'group'
  and P.perm_parameter not in (select group_name from cwd_group)
group by PS.name,P.perm_parameter

Navigate on JIRA to the Notification/Permission scheme returned by the query and remove the groups specified by the queries.