Member.joined_at can now be None

Discord making breaking changes :D

changes/1812.bugfix.md

@@ -0,0 +1,2 @@
+`Member.joined_at` is now nullable due to breaking API change
+ - This will be received on guest members with temporary membership

hikari/guilds.py

@@ -359,8 +359,12 @@ class Member(users.User):
     This will be `hikari.undefined.UNDEFINED` if it's state is unknown.
     """
 
-    joined_at: datetime.datetime = attrs.field(repr=True)
-    """The datetime of when this member joined the guild they belong to."""
+    joined_at: typing.Optional[datetime.datetime] = attrs.field(repr=True)
+    """The datetime of when this member joined the guild they belong to.
+    
+    This will be `None` for guest members that have been temporarily
+    invited.
+    """
 
     nickname: typing.Optional[str] = attrs.field(repr=True)
     """This member's nickname.

hikari/impl/entity_factory.py

@@ -1806,7 +1806,8 @@ def deserialize_member(
         if guild_id not in role_ids:
             role_ids.append(guild_id)
 
-        joined_at = time.iso8601_datetime_string_to_datetime(payload["joined_at"])
+        raw_joined_at = payload["joined_at"]
+        joined_at = time.iso8601_datetime_string_to_datetime(raw_joined_at) if raw_joined_at is not None else None
 
         raw_premium_since = payload.get("premium_since")
         premium_since = (

tests/hikari/impl/test_entity_factory.py

@@ -3230,7 +3230,7 @@ def test_deserialize_member_with_null_fields(self, entity_factory_impl, user_pay
             {
                 "nick": None,
                 "roles": ["11111", "22222", "33333", "44444"],
-                "joined_at": "2015-04-26T06:26:56.936000+00:00",
+                "joined_at": None,
                 "premium_since": None,
                 "deaf": False,
                 "avatar": None,
@@ -3244,6 +3244,7 @@ def test_deserialize_member_with_null_fields(self, entity_factory_impl, user_pay
         assert member.nickname is None
         assert member.premium_since is None
         assert member.guild_avatar_hash is None
+        assert member.joined_at is None
         assert isinstance(member, guild_models.Member)
 
     def test_deserialize_member_with_undefined_fields(self, entity_factory_impl, user_payload):