Sync: remove generic type from Diff

It doesn't play along well with NamedTuple due to metaclass conflicts.
The workaround involved created a NamedTuple-only base class, which
does work but at the cost of confusing some static type checkers.

Since Diff is now an internal data structure, it no longer really needs
to have precise type annotations. Therefore, a normal namedtuple is
adequate.

1 files changed, 10 insertions, 19 deletions

diff --git a/bot/cogs/sync/syncers.py b/bot/cogs/sync/syncers.py
index 7cc518348..394887bab 100644
--- a/bot/cogs/sync/syncers.py
+++ b/bot/cogs/sync/syncers.py
@@ -15,19 +15,10 @@ log = logging.getLogger(__name__)
 # something that we make use of when diffing site roles against guild roles.
 Role = namedtuple('Role', ('id', 'name', 'colour', 'permissions', 'position'))
 User = namedtuple('User', ('id', 'name', 'discriminator', 'avatar_hash', 'roles', 'in_guild'))
+Diff = namedtuple('Diff', ('created', 'updated', 'deleted'))
 
-_T = t.TypeVar("_T")
 
-
-class Diff(t.NamedTuple, t.Generic[_T]):
-    """The differences between the Discord cache and the contents of the database."""
-
-    created: t.Set[_T] = {}
-    updated: t.Set[_T] = {}
-    deleted: t.Set[_T] = {}
-
-
-class Syncer(abc.ABC, t.Generic[_T]):
+class Syncer(abc.ABC):
     """Base class for synchronising the database with objects in the Discord cache."""
 
     CONFIRM_TIMEOUT = 60 * 5  # 5 minutes
@@ -106,12 +97,12 @@ class Syncer(abc.ABC, t.Generic[_T]):
                 return False
 
     @abc.abstractmethod
-    async def _get_diff(self, guild: Guild) -> Diff[_T]:
+    async def _get_diff(self, guild: Guild) -> Diff:
         """Return the difference between the cache of `guild` and the database."""
         raise NotImplementedError
 
     @abc.abstractmethod
-    async def _sync(self, diff: Diff[_T]) -> None:
+    async def _sync(self, diff: Diff) -> None:
         """Perform the API calls for synchronisation."""
         raise NotImplementedError
 
@@ -143,12 +134,12 @@ class Syncer(abc.ABC, t.Generic[_T]):
             )
 
 
-class RoleSyncer(Syncer[Role]):
+class RoleSyncer(Syncer):
     """Synchronise the database with roles in the cache."""
 
     name = "role"
 
-    async def _get_diff(self, guild: Guild) -> Diff[Role]:
+    async def _get_diff(self, guild: Guild) -> Diff:
         """Return the difference of roles between the cache of `guild` and the database."""
         roles = await self.bot.api_client.get('bot/roles')
 
@@ -179,7 +170,7 @@ class RoleSyncer(Syncer[Role]):
 
         return Diff(roles_to_create, roles_to_update, roles_to_delete)
 
-    async def _sync(self, diff: Diff[Role]) -> None:
+    async def _sync(self, diff: Diff) -> None:
         """Synchronise the database with the role cache of `guild`."""
         for role in diff.created:
             await self.bot.api_client.post('bot/roles', json={**role._asdict()})
@@ -191,12 +182,12 @@ class RoleSyncer(Syncer[Role]):
             await self.bot.api_client.delete(f'bot/roles/{role.id}')
 
 
-class UserSyncer(Syncer[User]):
+class UserSyncer(Syncer):
     """Synchronise the database with users in the cache."""
 
     name = "user"
 
-    async def _get_diff(self, guild: Guild) -> Diff[User]:
+    async def _get_diff(self, guild: Guild) -> Diff:
         """Return the difference of users between the cache of `guild` and the database."""
         users = await self.bot.api_client.get('bot/users')
 
@@ -248,7 +239,7 @@ class UserSyncer(Syncer[User]):
 
         return Diff(users_to_create, users_to_update)
 
-    async def _sync(self, diff: Diff[User]) -> None:
+    async def _sync(self, diff: Diff) -> None:
         """Synchronise the database with the user cache of `guild`."""
         for user in diff.created:
             await self.bot.api_client.post('bot/users', json={**user._asdict()})