Implementing custom permission behavior?

I am not sure if this is a bug or a feature request or simply a frustrated user, but I am struggling with developing custom permission behavior - namely: preventing the deletion of published pages. If there is a way to do this without altering Wagtail source I am all ears, but here is a brief overview of my solution:

# Create custom PagePermissionTester and UserPagePermissionsProxy classes
class CustomPagePermissionTester(PagePermissionTester):
    def can_delete(self):
        return not self.page.live and super().can_delete()

class CustomPermProxy(UserPagePermissionsProxy):
    def for_page(self, page):
        return CustomPagePermissionTester(self, page)

# ... within my page model
    def permissions_for_user(self, user):
        user_perms = CustomPermProxy(user)
        return user_perms.for_page(self)

Within views/pages.py

def delete(request, page_id):
    page = get_object_or_404(Page, id=page_id).specific # access specific page type
    if not page.permissions_for_user(request.user).can_delete():
        raise PermissionDenied

And to remove the option to delete a page from the dropdown - simply add page_perms to the render context of def edit(request, page_id): and remove the following lines from the edit template:

{% page_permissions page as page_perms %}

Would something like the above be possible to implement for Wagtail as a whole or are there other reasons why overriding permissions_for_user should not be allowed?

[luizboaretto]

A system wide recycle bin and undelete would be very interesting.

[nickhudkins]

Hey @cjmochrie I just ran into this same issue, and noticed that the {% page_permissions %} template tag has this line in it: https://github.com/wagtail/wagtail/blob/de9ffaab4978ad5e50ead1c52b2c1036ee92fc0c/wagtail/wagtailadmin/templatetags/wagtailadmin_tags.py#L136

Unfortunately, those page permissions (although retrieved in the edit view: https://github.com/wagtail/wagtail/blob/de9ffaab4978ad5e50ead1c52b2c1036ee92fc0c/wagtail/wagtailadmin/views/pages.py#L301) go unused outside of the view. Which means that default Page permissions are used in context.

@gasman is this intended behavior or did we stumble on a bug?

The result of this is that if permissions_for_user is defined on a page sub class, the custom permissions returned are not respected.