[RFC] Added accept_request method to PageViewRestriction

[kaedroho]

This allows custom code to check whether a PageViewRestriction will pass
a request or not without needing to depend on any implementation
details.

[tomdyson]

@kaedroho could you please give an example of when this would be useful?

[kaedroho]

Yep, I currently have this bit of code in a client site. It works out whether a page is visible to the user or not, which I think is a common use-case:

@register.assignment_tag(takes_context=True)
def user_can_see_page(context, page):
    request = context['request']
    restrictions = page.get_view_restrictions()

    if restrictions:
        passed_restrictions = request.session.get('passed_page_view_restrictions', [])
        for restriction in restrictions:
            if restriction.restriction_type == PageViewRestriction.PASSWORD:
                if restriction.id not in passed_restrictions:
                    return False
            elif restriction.restriction_type == PageViewRestriction.LOGIN:
                if not user_is_authenticated(request.user):
                    return False
            elif restriction.restriction_type == PageViewRestriction.GROUPS:
                if not request.user.is_superuser:
                    current_user_groups = request.user.groups.all()

                    if not any(group in current_user_groups for group in restriction.groups.all()):
                        return False

    return True

But I think this logic really belongs in the PageViewRestriction model itself. This means that any future changes will automatically work with this site (currently, using an unsupported restriction type will cause this tag to pass).

Here's an example of this template tag written with the accept_request method:

@register.assignment_tag(takes_context=True)
def user_can_see_page(context, page):
    request = context['request']

    for restriction in page.get_view_restrictions():
        if not restriction.accept_request(request):
            return False

    return True

All the custom logic has now been removed, which is great for forwards compatibility.

[gasman]

Looks good to me!

The 'respond with an access-denied response' code that's been left behind in wagtail_hooks would also be a good candidate for turning a method on PageViewRestriction... but that's something for another time.

[gasman]

Merged in ba4119b.

[tomdyson]

Thanks for the explanation @kaedroho. Shouldn't we document the accept_request method, for future template tag authors?