Expanded view for Prefixes doesn't display hierarchy

[abrahamvegh]

Environment

• Python version: 3.7.3
• NetBox version: 2.8.3

Steps to Reproduce

Create a prefix that is a child of another prefix. e.g. 203.0.113.0/24 and 203.0.113.0/25

Expected Behavior

When viewing the list with the ‘Expand’ mode turned on, the prefixes used to display with an indication of their hierarchy.

Observed Behavior

All prefixes display at the same level in the list, making hierarchy less obvious.

Notes

I’m not sure exactly when this broke, but I'm pretty confident it was very recent, perhaps something in #492?

[jeremystretch]

I can confirm that this was broken by the change in #492. It seems that calling prefetch_related() on the queryset after annotate() wipes out the annotations, though I can't figure out why. AFAIK this shouldn't happen, but we may have run into some obscure caveat of the ORM.

[jeremystretch]

So we're not actually using annotate() to do this, but rather some convoluted logic in the annotate_depth() method on PrefixQuerySet. It's probably best to address this directly (which is already long overdue) rather than coming up with a workaround.

Marking this as blocked by #4639.

[jeremystretch]

I spent too much time today digging into #4639 and I'm afraid it isn't going anywhere soon. Going to throw in a "meh" workaround for an immediate fix for the UI.