Raise ImproperlyConfigured when Feed.link is missing instead of failing with AttributeError

[yureiblack]

Currently, the Feed.get_feed() method retrieves the feed's link using:

    link = self._get_dynamic_attr("link", obj)

If a Feed subclass does not define a link attribute, link becomes None.
This results in an unhelpful exception when Django later calls:

    link = add_domain(current_site.domain, link, request.is_secure())

Since add_domain() calls url.startswith(), a missing link
causes:

    AttributeError: 'NoneType' object has no attribute 'startswith'

This error does not clearly indicate the actual problem.

According to Django documentation, every Feed class must define
link. Therefore, it should raise a more appropriate and explicit
exception.

The attached PR adds the following check:

    if link is None:
        raise ImproperlyConfigured(
            "Feed class must define a 'link' attribute."
        )

This results in a clearer error message and avoids unexpected crashes.

PR: ​https://github.com/django/django/pull/20371

[Jacob Walls]

Seems reasonable, thanks. (I think this is the "better error" described as "wouldn't kill us" in a very similar scenario in ticket:2218#comment:1.)

Could you include a test?

[jaffar Khan]

Can I work on this ticket since the current owner no longer seems to be active?

[Vinay Datta]

Hi, I’ve worked on this issue and implemented a fix.

Previously, when Feed.link was missing, it resulted in an AttributeError. I’ve added an explicit check to ensure that link is present (and handled whether it is callable or not). Now, if it is missing or evaluates to an empty value, it raises ImproperlyConfigured with a clear error message instead.

I’ve also verified that the change prevents the unintended AttributeError and provides a more appropriate and developer-friendly exception.

Please let me know if you’d like me to add or adjust tests for this behavior before I open a PR.