usethis-python · nathanjmcdougall · Mar 21, 2026 · Mar 21, 2026
diff --git a/pyproject.toml b/pyproject.toml
@@ -213,7 +213,6 @@ reportCallInDefaultInitializer = false
 reportExplicitAny = false
 reportImplicitOverride = false
 reportImplicitStringConcatenation = false
-reportInvalidAbstractMethod = false
 reportMissingParameterType = false
 reportMissingTypeArgument = false
 reportMissingTypeStubs = false

diff --git a/src/usethis/_file/ini/io_.py b/src/usethis/_file/ini/io_.py
@@ -2,6 +2,7 @@
 
 import configparser
 import re
+from abc import ABCMeta
 from typing import TYPE_CHECKING
 
 from configupdater import ConfigUpdater as INIDocument
@@ -38,7 +39,7 @@
     )
 
 
-class INIFileManager(KeyValueFileManager):
+class INIFileManager(KeyValueFileManager, metaclass=ABCMeta):
     _content_by_path: ClassVar[dict[Path, INIDocument | None]] = {}
 
     def __enter__(self) -> Self:

diff --git a/src/usethis/_file/toml/io_.py b/src/usethis/_file/toml/io_.py
@@ -2,6 +2,7 @@
 
 import copy
 import re
+from abc import ABCMeta
 from typing import TYPE_CHECKING, Any
 
 import tomlkit.api
@@ -42,7 +43,7 @@
     from usethis._io import Key
 
 
-class TOMLFileManager(KeyValueFileManager):
+class TOMLFileManager(KeyValueFileManager, metaclass=ABCMeta):
     """An abstract class for managing TOML files."""
 
     _content_by_path: ClassVar[dict[Path, TOMLDocument | None]] = {}

diff --git a/src/usethis/_file/yaml/io_.py b/src/usethis/_file/yaml/io_.py
@@ -2,6 +2,7 @@
 
 import copy
 import re
+from abc import ABCMeta
 from contextlib import contextmanager
 from dataclasses import dataclass
 from io import StringIO
@@ -44,7 +45,7 @@
     from usethis._io import Key
 
 
-class YAMLFileManager(KeyValueFileManager):
+class YAMLFileManager(KeyValueFileManager, metaclass=ABCMeta):
     """An abstract class for managing YAML files."""
 
     _content_by_path: ClassVar[dict[Path, YAMLDocument | None]] = {}

diff --git a/src/usethis/_io.py b/src/usethis/_io.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import re
-from abc import abstractmethod
+from abc import ABCMeta, abstractmethod
 from typing import TYPE_CHECKING, Generic, TypeAlias, TypeVar
 
 from typing_extensions import assert_never
@@ -29,7 +29,7 @@ class UnexpectedFileIOError(UsethisError, IOError):
     """Raised when an unexpected attempt is made to read or write the pyproject.toml file."""
 
 
-class UsethisFileManager(Generic[DocumentT]):
+class UsethisFileManager(Generic[DocumentT], metaclass=ABCMeta):
     """Manages file access with deferred writes using a context manager.
 
     This class implements the Command Pattern, encapsulating file operations. It defers
@@ -180,7 +180,7 @@ def unlock(self) -> None:
 Key: TypeAlias = str | re.Pattern[str]
 
 
-class KeyValueFileManager(UsethisFileManager, Generic[DocumentT]):
+class KeyValueFileManager(UsethisFileManager, Generic[DocumentT], metaclass=ABCMeta):
     """A manager for files which store (at least some) values in key-value mappings."""
 
     @abstractmethod

diff --git a/src/usethis/_tool/spec.py b/src/usethis/_tool/spec.py
@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from abc import abstractmethod
+from abc import ABCMeta, abstractmethod
 from dataclasses import dataclass, field
 from typing import TYPE_CHECKING, Protocol
 
@@ -42,7 +42,7 @@ class ToolMeta:
     url: str | None = None  # For documentation purposes
 
 
-class ToolSpec(Protocol):
+class ToolSpec(Protocol, metaclass=ABCMeta):
     @property
     @abstractmethod
     def meta(self) -> ToolMeta: ...

diff --git a/tests/usethis/test_io.py b/tests/usethis/test_io.py
@@ -13,6 +13,12 @@ class MyUsethisFileManager(UsethisFileManager):
                 def relative_path(self) -> Path:
                     return Path("pyproject.toml")
 
+                def _dump_content(self) -> str:
+                    raise NotImplementedError
+
+                def _parse_content(self, content: str) -> None:
+                    raise NotImplementedError
+
             with change_cwd(tmp_path):
                 manager = MyUsethisFileManager()
 
@@ -30,6 +36,12 @@ class MyUsethisFileManager(UsethisFileManager):
                 def relative_path(self) -> Path:
                     return Path("pyproject.toml")
 
+                def _dump_content(self) -> str:
+                    raise NotImplementedError
+
+                def _parse_content(self, content: str) -> None:
+                    raise NotImplementedError
+
             manager = MyUsethisFileManager()
             other_manager = MyUsethisFileManager()
 
@@ -46,6 +58,12 @@ class MyUsethisFileManager(UsethisFileManager):
                 def relative_path(self) -> Path:
                     return Path("pyproject.toml")
 
+                def _dump_content(self) -> str:
+                    raise NotImplementedError
+
+                def _parse_content(self, content: str) -> None:
+                    raise NotImplementedError
+
             manager = MyUsethisFileManager()
             other_manager = object()
 
@@ -63,6 +81,12 @@ class MyUsethisFileManager(UsethisFileManager):
                 def relative_path(self) -> Path:
                     return Path("pyproject.toml")
 
+                def _dump_content(self) -> str:
+                    raise NotImplementedError
+
+                def _parse_content(self, content: str) -> None:
+                    raise NotImplementedError
+
             with change_cwd(tmp_path):
                 manager = MyUsethisFileManager()