Renamed the AbstractUserUtils class to UserUtilityInterface, and added the can_view and can_edit functions to the UserUtilityInterface interface. There is no need to separately supply two additional can_view and can_edit callbacks.

src/accounting/__init__.py

@@ -23,7 +23,7 @@ from pathlib import Path
 from flask import Flask, Blueprint
 from flask_sqlalchemy import SQLAlchemy
 
-from accounting.utils.user import AbstractUserUtils
+from accounting.utils.user import UserUtilityInterface
 
 db: SQLAlchemy = SQLAlchemy()
 """The database instance."""
@@ -31,19 +31,13 @@ data_dir: Path = Path(__file__).parent / "data"
 """The data directory."""
 
 
-def init_app(app: Flask, user_utils: AbstractUserUtils,
+def init_app(app: Flask, user_utils: UserUtilityInterface,
-             url_prefix: str = "/accounting",
+             url_prefix: str = "/accounting") -> None:
-             can_view_func: t.Callable[[], bool] | None = None,
-             can_edit_func: t.Callable[[], bool] | None = None) -> None:
     """Initialize the application.
 
     :param app: The Flask application.
     :param user_utils: The user utilities.
     :param url_prefix: The URL prefix of the accounting application.
-    :param can_view_func: A callback that returns whether the current user can
-        view the accounting data.
-    :param can_edit_func: A callback that returns whether the current user can
-        edit the accounting data.
     :return: None.
     """
     # The database instance must be set before loading everything
@@ -73,7 +67,7 @@ def init_app(app: Flask, user_utils: AbstractUserUtils,
     locale.init_app(app, bp)
 
     from .utils import permission
-    permission.init_app(bp, can_view_func, can_edit_func)
+    permission.init_app(bp, user_utils)
 
     from .utils import next_uri
     next_uri.init_app(bp)

src/accounting/utils/permission.py

@@ -23,7 +23,7 @@ import typing as t
 
 from flask import abort, Blueprint
 
-from accounting.utils.user import get_current_user
+from accounting.utils.user import get_current_user, UserUtilityInterface
 
 
 def has_permission(rule: t.Callable[[], bool]) -> t.Callable:
@@ -87,22 +87,15 @@ def can_edit() -> bool:
     return __can_edit_func()
 
 
-def init_app(bp: Blueprint,
+def init_app(bp: Blueprint, user_utils: UserUtilityInterface) -> None:
-             can_view_func: t.Callable[[], bool] | None = None,
-             can_edit_func: t.Callable[[], bool] | None = None) -> None:
     """Initializes the application.
 
     :param bp: The blueprint of the accounting application.
-    :param can_view_func: A callback that returns whether the current user can
+    :param user_utils: The user utilities.
-        view the accounting data.
-    :param can_edit_func: A callback that returns whether the current user can
-        edit the accounting data.
     :return: None.
     """
     global __can_view_func, __can_edit_func
-    if can_view_func is not None:
+    __can_view_func = user_utils.can_view
-        __can_view_func = can_view_func
+    __can_edit_func = user_utils.can_edit
-    if can_edit_func is not None:
+    bp.add_app_template_global(user_utils.can_view, "accounting_can_view")
-        __can_edit_func = can_edit_func
+    bp.add_app_template_global(user_utils.can_edit, "accounting_can_edit")
-    bp.add_app_template_global(can_view, "accounting_can_view")
-    bp.add_app_template_global(can_edit, "accounting_can_edit")

src/accounting/utils/user.py

@@ -29,8 +29,26 @@ from flask_sqlalchemy.model import Model
 T = t.TypeVar("T", bound=Model)
 
 
-class AbstractUserUtils(t.Generic[T], ABC):
+class UserUtilityInterface(t.Generic[T], ABC):
-    """The abstract user utilities."""
+    """The interface for the user utilities."""
+
+    @abstractmethod
+    def can_view(self) -> bool:
+        """Returns whether the currently logged-in user can view the accounting
+        data.
+
+        :return: True if the currently logged-in user can view the accounting
+            data, or False otherwise.
+        """
+
+    @abstractmethod
+    def can_edit(self) -> bool:
+        """Returns whether the currently logged-in user can edit the accounting
+        data.
+
+        :return: True if the currently logged-in user can edit the accounting
+            data, or False otherwise.
+        """
 
     @property
     @abstractmethod
@@ -72,7 +90,7 @@ class AbstractUserUtils(t.Generic[T], ABC):
         """
 
 
-__user_utils: AbstractUserUtils
+__user_utils: UserUtilityInterface
 """The user utilities."""
 user_cls: t.Type[Model] = Model
 """The user class."""
@@ -80,7 +98,7 @@ user_pk_column: sa.Column = sa.Column(sa.Integer)
 """The primary key column of the user class."""
 
 
-def init_user_utils(utils: AbstractUserUtils) -> None:
+def init_user_utils(utils: UserUtilityInterface) -> None:
     """Initializes the user utilities.
 
     :param utils: The user utilities.

tests/test_site/__init__.py

@@ -29,8 +29,6 @@ from flask_sqlalchemy import SQLAlchemy
 from flask_wtf import CSRFProtect
 from sqlalchemy import Column
 
-import accounting.utils.user
-
 bp: Blueprint = Blueprint("home", __name__)
 babel_js: BabelJS = BabelJS()
 csrf: CSRFProtect = CSRFProtect()
@@ -69,7 +67,16 @@ def create_app(is_testing: bool = False) -> Flask:
     from . import auth
     auth.init_app(app)
 
-    class UserUtils(accounting.utils.user.AbstractUserUtils[auth.User]):
+    class UserUtilities(accounting.UserUtilityInterface[auth.User]):
+
+        def can_view(self) -> bool:
+            return auth.current_user() is not None \
+                and auth.current_user().username in ["viewer", "editor",
+                                                     "editor2"]
+
+        def can_edit(self) -> bool:
+            return auth.current_user() is not None \
+                and auth.current_user().username in ["editor", "editor2"]
 
         @property
         def cls(self) -> t.Type[auth.User]:
@@ -90,12 +97,7 @@ def create_app(is_testing: bool = False) -> Flask:
         def get_pk(self, user: auth.User) -> int:
             return user.id
 
-    can_view: t.Callable[[], bool] = lambda: auth.current_user() is not None \
+    accounting.init_app(app, user_utils=UserUtilities())
-        and auth.current_user().username in ["viewer", "editor", "editor2"]
-    can_edit: t.Callable[[], bool] = lambda: auth.current_user() is not None \
-        and auth.current_user().username in ["editor", "editor2"]
-    accounting.init_app(app, user_utils=UserUtils(),
-                        can_view_func=can_view, can_edit_func=can_edit)
 
     return app