Admin action 'Delete selected' check only global model delete permission

[krejcik@…]

Action 'delete_selected' calls ModelAdmin's has_delete_permission method only once without obj argument.
(This action is run from object list with checked records)
It is problem if has_delete_permission contains more complex logic which returns different values for a particular objects.
If one of deleted objects must not be delete whole action should fail.

Simple workaround is always forbid global delete (it means return False if obj argument is not given) and allow delete only for specified objects.
But such solutuion still disallow to do multiple delete on objects which can be deleted separately from it's detail form.

[whiskybar]

Since no one has commented on this issue, I will try to put it another way.

Deleting objects in the admin is inconsistent between

• deleting object by the action delete_selected

• deleting object from the detail view in the change form

The action delete_selected does not check has_delete_permission for each selected object. Instead, it calls has_delete_permission for all objects.
On the other hand, the admin will check if one has permission to delete the specific object in the view (the change form).

You have to disable the action delete_selected virtually if has_delete_permission is in effect. In my humble opinion, the admin should call has_delete_permission for each selected object with the action delete_selected.

[Julien Phalip]

Related issue: #13539.

[Julien Phalip]

Check #10609 for yet another related issue.

[Al Johri]

Running into exactly this issue. Is this documented somewhere?

[adsworth]

What would the preferred UX be for this?

1. on POST, abort on the first object for which modeladmin.has_permission returns False, with a message that the user doesn't have permission to delete the obj.
2. on POST, iterate over all objects in the queryset and collect the ones modeladmin.has_permission returns False for. If any can't be deleted then abort the action with a list of records which couldn't be delete.
3. on POST, iterate over all objects in the queryset and only delete the ones modeladmin.has_permission returns True for and add an the admin message for the user stating that N objects were skipped.
4. on POST, iterate over all objects in the queryset and collect the ones modeladmin.has_permission returns False for. If any can't be deleted display them to the user and ask him if he want's to delete the other ones.
5. on the confirm deletion page split the list in two parts. First part lists the deletable objects, second part lists the non deletable objects. Then on POST submit the deletable object IDs and only delete those.

If we start checking for object permissions here, this actually open the whole box of how to handle the related objects. All the related objects are already iterated using admin.utils.get_deleted_objects, but this only calls user.has_perm

[Ray Logel]

There is a way to enforce bulk action deletes based on per object permissions. We used the following approach:

def has_delete_permission(self, request, obj=None):
    # Only superusers can delete
    if not request.user.is_superuser:
        return False

    if obj:
        # Code to check if obj is allowed to be deleted
        can_delete = .....
        return can_delete

    # Check if multiple items are selected to be deleted
    if (
        request.path.startswith('/admin/<path_to_model_being_deleted>') and
        request.POST and request.POST.get('action') == 'delete_selected'
    ):
        # Get list of ids that are going to be deleted
        id_list = request.POST.getlist(admin.helpers.ACTION_CHECKBOX_NAME)

        # Use id_list to lookup object or perform some query to see if that object can be deleted
        for id in id_list:
            can_delete = ....
            if not can_delete:
                # This object can't be deleted so return False to prevent entire request
                return False

    # User has delete permissions
    return True

# If you want a custom error message
def delete_selected(self, request, queryset):
    if not self.has_delete_permission(request):
        # You can also use request.POST.getlist(admin.helpers.ACTION_CHECKBOX_NAME)
        # to generate a even more detailed message.
        messages.error(request, "One of the items selected can't be deleted")
        return

    return actions.delete_selected(self, request, queryset)

delete_selected.short_description = actions.delete_selected.short_description

actions = [delete_selected]

Unfortunately this approach no longer generates an appropriate error message as of 2.1 because the has_delete_permission method is also used to filter the actions. So it will prevent the delete from happening but it just prints a warning No action selected because the action is filtered out before it can get to the actual delete permission check.

[Ray Logel]

If the ModelAdmin._filter_actions_by_permissions method were updated so that it passed in some variable to the has_permission function to identify that it was being used to filter the actions the has_delete_permission could act accordingly. Then when AdminViewPermissionBaseModelAdmin.get_model_perms calls has_delete_permission it can differentiate from the action filter and return false with an appropriate error message.

[Ray Logel]

I just realized you can use the error message work around to solve the issue introduced in 2.1.

def has_delete_permission(self, request, obj=None):
    # Only superusers can delete
    if not request.user.is_superuser:
        return False

    if obj:
        # Code to check if obj is allowed to be deleted
        can_delete = .....
        return can_delete

    # Bulk deletes will be verified in the overridden delete_selected method below
    return True

# Override the delete_selected action
def delete_selected(self, request, queryset):
    # Check if multiple items are selected to be deleted
    if (
        request.path.startswith('/admin/<path_to_model_being_deleted>') and
        request.POST and request.POST.get('action') == 'delete_selected'
    ):
        # Get list of ids that are going to be deleted
        id_list = request.POST.getlist(admin.helpers.ACTION_CHECKBOX_NAME)

        # Use id_list to lookup object or perform some query to see if that object can be deleted
        for id in id_list:
            can_delete = ....
            if not can_delete:
                messages.error(request, "One of the items selected can't be deleted")
                return  # Don't perform delete

    # Call the actual delete method
    return actions.delete_selected(self, request, queryset)

delete_selected.short_description = actions.delete_selected.short_description

actions = [delete_selected]