Make settings a singleton

pyproject.toml

@@ -9,6 +9,7 @@ readme = "README.md"
 [tool.poetry.dependencies]
 python = "<3.13,>=3.9"
 typing-extensions = "^4.12.2"
+pytest-asyncio = "^0.24.0"
 
 
 [tool.poetry.group.dev.dependencies]

vintasend/app_settings.py

@@ -1,6 +1,8 @@
 import os
 from typing import Any, TypedDict, cast
 
+from vintasend.utils.singleton_utils import SingletonMeta
+
 
 class NotificationSettingsDict(TypedDict):
     NOTIFICATION_ADAPTERS: list[tuple[str, str]]
@@ -132,7 +134,7 @@ def get_config(setting_name: str, config: Any = None):
         return {}
 
 
-class NotificationSettings:
+class NotificationSettings(metaclass=SingletonMeta):
     NOTIFICATION_ADAPTERS: list[tuple[str, str]]
     NOTIFICATION_BACKEND: str
     NOTIFICATION_MODEL: str | None

vintasend/services/helpers.py

@@ -57,10 +57,11 @@ def get_notification_adapters(
     config: Any = None,
 ) -> list[BaseNotificationAdapter]:
     default_adapters = []
+    app_settings = NotificationSettings(config)
     adapters_imports_strs_with_default = (
         adapters_imports_strs
         if adapters_imports_strs is not None
-        else NotificationSettings(config).NOTIFICATION_ADAPTERS
+        else app_settings.NOTIFICATION_ADAPTERS
     )
     for adapter_import_str, template_renderer_import_str in adapters_imports_strs_with_default:
         adapter_kwargs: dict = {}
@@ -77,7 +78,7 @@ def get_notification_adapters(
         try:
             adapter = adapter_cls(
                 template_renderer_import_str,
-                backend if backend else NotificationSettings().NOTIFICATION_BACKEND,
+                backend if backend else app_settings.NOTIFICATION_BACKEND,
                 backend_kwargs,
                 config,
                 **adapter_kwargs,
@@ -106,10 +107,11 @@ def get_asyncio_notification_adapters(
     config: Any = None,
 ) -> list[AsyncIOBaseNotificationAdapter]:
     default_adapters = []
+    app_settings = NotificationSettings(config)
     adapters_imports_strs_with_default = (
         adapters_imports_strs
         if adapters_imports_strs is not None
-        else NotificationSettings(config).NOTIFICATION_ADAPTERS
+        else app_settings.NOTIFICATION_ADAPTERS
     )
     for adapter_import_str, template_renderer_import_str in adapters_imports_strs_with_default:
         adapter_kwargs: dict = {}
@@ -125,7 +127,7 @@ def get_asyncio_notification_adapters(
         try:
             adapter = adapter_cls(
                 template_renderer_import_str,
-                backend if backend else NotificationSettings().NOTIFICATION_BACKEND,
+                backend if backend else app_settings.NOTIFICATION_BACKEND,
                 backend_kwargs,
                 config,
                 **adapter_kwargs,
@@ -147,10 +149,11 @@ def get_asyncio_notification_adapters(
 def get_notification_backend(
     backend_import_str: str | None, backend_kwargs: dict | None = None, config: Any = None
 ) -> BaseNotificationBackend:
+    app_settings = NotificationSettings(config)
     backend_import_str_with_fallback = (
         backend_import_str
         if backend_import_str is not None
-        else NotificationSettings(config).NOTIFICATION_BACKEND
+        else app_settings.NOTIFICATION_BACKEND
     )
 
     try:
@@ -177,10 +180,11 @@ def get_notification_backend(
 def get_asyncio_notification_backend(
     backend_import_str: str | None, backend_kwargs: dict | None = None, config: Any = None
 ) -> AsyncIOBaseNotificationBackend:
+    app_settings = NotificationSettings(config)
     backend_import_str_with_fallback = (
         backend_import_str
         if backend_import_str is not None
-        else NotificationSettings(config).NOTIFICATION_BACKEND
+        else app_settings.NOTIFICATION_BACKEND
     )
 
     try:

vintasend/services/notification_service.py

@@ -5,6 +5,7 @@
 from collections.abc import Callable, Iterable
 from typing import Any, ClassVar, Generic, TypeGuard, TypeVar, cast
 
+from vintasend.app_settings import NotificationSettings
 from vintasend.services.notification_backends.asyncio_base import AsyncIOBaseNotificationBackend
 
 
@@ -81,6 +82,10 @@ def __init__(
         notification_backend_kwargs: dict | None = None,
         config: Any = None,
     ):
+        # initialize the notification settings singleton for the first time
+        # to ensure all components have access to the same settings
+        NotificationSettings(config)
+
         if isinstance(notification_backend, BaseNotificationBackend):
             self.notification_backend = cast(B, notification_backend)
         else:

vintasend/utils/singleton_utils.py

@@ -1,13 +1,20 @@
 from types import MappingProxyType
-from typing import Any
+from typing import Any, Generic, TypeVar, cast
 
 
-class SingletonMeta(type):
-    _instances: MappingProxyType[str, Any] = MappingProxyType({})
+class BaseSingletonMeta(type):
+    _instances: MappingProxyType[Any, Any]
 
-    def __call__(cls, *args, **kwargs):
+
+T = TypeVar('T', bound=BaseSingletonMeta)
+
+
+class SingletonMeta(Generic[T], BaseSingletonMeta):
+    _instances: MappingProxyType["SingletonMeta[T]", T] = MappingProxyType({})
+
+    def __call__(cls, *args: Any, **kwargs: Any) -> T:
         if cls not in cls._instances:
-            cls._instances = dict(cls._instances)
-            cls._instances[cls] = super().__call__(*args, **kwargs)
-            cls._instances = MappingProxyType(cls._instances)
+            _instances: dict["SingletonMeta[T]", T] = dict(cls._instances)
+            _instances[cls] = cast(T, super().__call__(*args, **kwargs))
+            cls._instances = MappingProxyType(_instances)
         return cls._instances[cls]