Cache follow button template snippet

bookwyrm/models/relationship.py

@@ -1,5 +1,7 @@
 """ defines relationships between users """
 from django.apps import apps
+from django.core.cache import cache
+from django.core.cache.utils import make_template_fragment_key
 from django.db import models, transaction, IntegrityError
 from django.db.models import Q
 
@@ -36,6 +38,20 @@ class UserRelationship(BookWyrmModel):
         """the remote user needs to recieve direct broadcasts"""
         return [u for u in [self.user_subject, self.user_object] if not u.local]
 
+    def save(self, *args, **kwargs):
+        """clear the template cache"""
+        # invalidate the template cache
+        cache_keys = [
+            make_template_fragment_key(
+                "follow_button", [self.user_subject.id, self.user_object.id]
+            ),
+            make_template_fragment_key(
+                "follow_button", [self.user_object.id, self.user_subject.id]
+            ),
+        ]
+        cache.delete_many(cache_keys)
+        super().save(*args, **kwargs)
+
     class Meta:
         """relationships should be unique"""
 

bookwyrm/templates/snippets/follow_button.html

@@ -1,4 +1,7 @@
 {% load i18n %}
+{% load cache %}
+
+{% cache None follow_button request.user.id user.id %}
 {% if request.user == user or not request.user.is_authenticated %}
 {% elif user in request.user.blocks.all %}
 {% include 'snippets/block_button.html' with blocks=True %}
@@ -42,3 +45,4 @@
     {% endif %}
 </div>
 {% endif %}
+{% endcache %}