[V3 Config] Require custom group initialization before usage (#2545)

* Require custom group initialization before usage and write that data to disk

* Style

* add tests

* remove custom info update method from drivers

* clean up remnant

* Turn config objects into a singleton to deal with custom group identifiers

* Fix dumbassery

* Stupid stupid stupid

redbot/core/config.py

@@ -2,6 +2,7 @@ import logging
 import collections
 from copy import deepcopy
 from typing import Any, Union, Tuple, Dict, Awaitable, AsyncContextManager, TypeVar, TYPE_CHECKING
+import weakref
 
 import discord
 
@@ -15,6 +16,8 @@ log = logging.getLogger("red.config")
 
 _T = TypeVar("_T")
 
+_config_cache = weakref.WeakValueDictionary()
+
 
 class _ValueCtxManager(Awaitable[_T], AsyncContextManager[_T]):
     """Context manager implementation of config values.
@@ -514,6 +517,19 @@ class Config:
     USER = "USER"
     MEMBER = "MEMBER"
 
+    def __new__(cls, cog_name, unique_identifier, *args, **kwargs):
+        key = (cog_name, unique_identifier)
+
+        if key[0] is None:
+            raise ValueError("You must provide either the cog instance or a cog name.")
+
+        if key in _config_cache:
+            conf = _config_cache[key]
+        else:
+            conf = object.__new__(cls)
+            _config_cache[key] = conf
+        return conf
+
     def __init__(
         self,
         cog_name: str,
@@ -529,6 +545,8 @@ class Config:
         self.force_registration = force_registration
         self._defaults = defaults or {}
 
+        self.custom_groups = {}
+
     @property
     def defaults(self):
         return deepcopy(self._defaults)
@@ -788,13 +806,32 @@ class Config:
         """
         self._register_default(group_identifier, **kwargs)
 
+    def init_custom(self, group_identifier: str, identifier_count: int):
+        """
+        Initializes a custom group for usage. This method must be called first!
+        """
+        if group_identifier in self.custom_groups:
+            raise ValueError(f"Group identifier already registered: {group_identifier}")
+
+        self.custom_groups[group_identifier] = identifier_count
+
     def _get_base_group(self, category: str, *primary_keys: str) -> Group:
+        is_custom = category not in (
+            self.GLOBAL,
+            self.GUILD,
+            self.USER,
+            self.MEMBER,
+            self.ROLE,
+            self.CHANNEL,
+        )
         # noinspection PyTypeChecker
         identifier_data = IdentifierData(
             uuid=self.unique_identifier,
             category=category,
             primary_key=primary_keys,
             identifiers=(),
+            custom_group_data=self.custom_groups,
+            is_custom=is_custom,
         )
         return Group(
             identifier_data=identifier_data,
@@ -902,6 +939,8 @@ class Config:
             The custom group's Group object.
 
         """
+        if group_identifier not in self.custom_groups:
+            raise ValueError(f"Group identifier not initialized: {group_identifier}")
         return self._get_base_group(str(group_identifier), *map(str, identifiers))
 
     async def _all_from_scope(self, scope: str) -> Dict[int, Dict[Any, Any]]:
@@ -1072,7 +1111,9 @@ class Config:
         """
         if not scopes:
             # noinspection PyTypeChecker
-            identifier_data = IdentifierData(self.unique_identifier, "", (), ())
+            identifier_data = IdentifierData(
+                self.unique_identifier, "", (), (), self.custom_groups
+            )
             group = Group(identifier_data, defaults={}, driver=self.driver)
         else:
             group = self._get_base_group(*scopes)