ids.translate_user_id: follow use_instead

ids.py

@@ -36,8 +36,13 @@ def translate_user_id(*, id, from_proto, to_proto):
     if from_proto == to_proto:
         return id
 
+    # follow use_instead
+    user = from_proto.get_by_id(id)
+    if user:
+        id = user.key.id()
+
     def copy_or_original():
-        if user := from_proto.get_by_id(id):
+        if user:
             if copy := user.get_copy(to_proto):
                 return copy
         if orig := models.get_original(id):

tests/test_ids.py

@@ -58,6 +58,22 @@ class IdsTest(TestCase):
                 self.assertIsNone(translate_user_id(
                     id='did:plc:123', from_proto=ATProto, to_proto=proto))
 
+    def test_translate_user_id_use_instead(self):
+        did = Target(uri='did:plc:123', protocol='atproto')
+        user = self.make_user('user.com', cls=Web, copies=[did])
+        self.make_user('www.user.com', cls=Web, use_instead=user.key)
+
+        for proto, expected in [
+            (ATProto, 'did:plc:123'),
+            (ActivityPub, 'http://localhost/user.com'),
+            (Fake, 'fake:u:user.com'),
+        ]:
+            with self.subTest(proto=proto.LABEL):
+                self.assertEqual(expected, translate_user_id(
+                    id='www.user.com', from_proto=Web, to_proto=proto))
+                self.assertEqual(expected, translate_user_id(
+                    id='https://www.user.com/', from_proto=Web, to_proto=proto))
+
     def test_translate_handle(self):
         for from_, handle, to, expected in [
             # basic