Partial checkin. The "followers" property on RemotePersons and LocalPersons is now handled separately.

On a LocalPerson, our own models are the authoritative source for their followers.
On a RemotePerson, we have to grab the list from the remote server.

I've made some tests for the LocalPerson part, but the RemotePerson part
still needs testing. This has involved creating a test_person module
in trilby, because test_account is for integration tests.

kepi/trilby_api/models/person.py

@@ -105,12 +105,6 @@ class Person(PolymorphicModel):
         # this matches the behaviour of Mastodon
         return self.url
 
-    @property
-    def followers(self):
-        return Person.objects.filter(
-            rel_following__following = self,
-            )
-
     @property
     def following(self):
         return Person.objects.filter(
@@ -242,6 +236,48 @@ class RemotePerson(Person):
 
         return None
 
+    @property
+    def followers(self):
+        from kepi.sombrero_sendpub.fetch import fetch
+        from kepi.sombrero_sendpub.collections import Collection
+
+        class RemotePersonFollowers(object):
+            def __init__(self, address):
+                logger.debug(
+                        "Initialising RemotePerson's followers iterator: %s",
+                        address,
+                        )
+
+                self.collection = None
+                self.address = address
+
+            def __iter__(self):
+                self.collection = fetch(
+                        self.address,
+                        Collection,
+                        )
+                return self
+
+            def __next__(self):
+
+                url = self.collection.__next__()
+
+                logger.debug("Next follower is at %s", url)
+
+                person = fetch(
+                        url,
+                        Person,
+                        )
+                logger.debug("  -- which is %s", person)
+
+                return person
+
+        result = RemotePersonFollowers(
+                self.followers_url,
+                )
+
+        return result
+
 ########################################
 
 class TrilbyUser(AbstractUser):
@@ -476,6 +512,12 @@ class LocalPerson(Person):
 
         return result
 
+    @property
+    def followers(self):
+        return Person.objects.filter(
+            rel_following__following = self,
+            )
+
     def inbox_url(self):
         return uri_to_url(settings.KEPI['USER_INBOX_LINK'] % {
             'username': self.local_user.username,

kepi/trilby_api/tests/test_person.py

@@ -0,0 +1,35 @@
+# test_person.py
+#
+# Part of kepi.
+# Copyright (c) 2018-2020 Marnanel Thurman.
+# Licensed under the GNU Public License v2.
+
+from kepi.trilby_api.tests import *
+from unittest import skip
+from rest_framework.test import APIClient, force_authenticate
+import logging
+
+logger = logging.getLogger(name='kepi')
+
+# This needs expanding into a full unit test.
+
+class TestPerson(TrilbyTestCase):
+
+    def test_followers(self):
+
+        alice = create_local_person(name='alice')
+        bob = create_local_person(name='bob')
+        carol = create_local_person(name='carol')
+
+        Follow(follower=bob, following=alice).save()
+        Follow(follower=carol, following=alice).save()
+
+        followers = sorted(list(
+            [x.url for x in alice.followers]))
+
+        self.assertEqual(
+                followers,
+                ['https://testserver/users/bob', 'https://testserver/users/carol']
+        )
+
+        # FIXME test the "followers" property on a RemotePerson