usethis-python · nathanjmcdougall · Mar 13, 2026 · Mar 13, 2026 · Mar 13, 2026 · Mar 13, 2026
diff --git a/pyproject.toml b/pyproject.toml
@@ -224,14 +224,14 @@ reportUnannotatedClassAttribute = false
 reportUnknownArgumentType = false
 reportUnknownLambdaType = false
 reportUnknownMemberType = false
-reportUnknownParameterType = false
 reportUnknownVariableType = false
 reportUnnecessaryIsInstance = false
 reportUnusedCallResult = false
 reportUnusedParameter = false
 
 [[tool.basedpyright.executionEnvironments]]
 root = "tests"
+reportUnknownParameterType = false
 reportUnreachable = false
 reportUnusedFunction = false
 

diff --git a/src/usethis/_file/yaml/update.py b/src/usethis/_file/yaml/update.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from difflib import SequenceMatcher
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, TypeVar
 
 from ruamel.yaml.comments import (
     CommentedMap,
@@ -12,6 +12,8 @@
 
     from usethis._file.yaml.typing_ import YAMLLiteral
 
+_T = TypeVar("_T")
+
 
 def update_ruamel_yaml_map(
     cmap: YAMLLiteral | dict[str, Any],
@@ -64,7 +66,7 @@ def update_ruamel_yaml_map(
         cmap[key] = cmap_copy[key]
 
 
-def lcs_list_update(original: list, new: list) -> None:
+def lcs_list_update(original: list[_T], new: list[_T]) -> None:
     """Update in-place using a longest common subsequence solver.
 
     This makes `original` identical to `new`, but respects subtypes of list such as

diff --git a/src/usethis/_io.py b/src/usethis/_io.py
@@ -177,7 +177,7 @@ def unlock(self) -> None:
         self._content_by_path.pop(self.path, None)
 
 
-Key: TypeAlias = str | re.Pattern
+Key: TypeAlias = str | re.Pattern[str]
 
 
 class KeyValueFileManager(UsethisFileManager, Generic[DocumentT]):

diff --git a/src/usethis/_pipeweld/containers.py b/src/usethis/_pipeweld/containers.py
@@ -15,10 +15,10 @@ class Series(RootModel[list["Series | Parallel | DepGroup | str"]]):
     def __hash__(self):
         return hash((_HASH_SALT, tuple(self.root)))
 
-    def __getitem__(self, item):
+    def __getitem__(self, item: int) -> Series | Parallel | DepGroup | str:
         return self.root[item]
 
-    def __setitem__(self, item, value):
+    def __setitem__(self, item: int, value: Series | Parallel | DepGroup | str) -> None:
         self.root[item] = value
 
     def __eq__(self, other: Any):

diff --git a/src/usethis/_pipeweld/func.py b/src/usethis/_pipeweld/func.py
@@ -250,10 +250,11 @@ def _insert_before_postrequisites(
                 idx=-1,
                 predecessor=predecessor,
             )
-            if len(container) == 1 and container[0] == _union(
-                successor_component, self.step
-            ):
-                component[idx + 1] = _union(successor_component, self.step)
+            union = _union(successor_component, self.step)
+            if len(container) == 1 and container[0] == union:
+                if union is None:
+                    raise NotImplementedError
+                component[idx + 1] = union
 
             return instructions
         elif isinstance(successor_component, Parallel | DepGroup | str):

diff --git a/src/usethis/_tool/base.py b/src/usethis/_tool/base.py
@@ -235,7 +235,7 @@ def migrate_config_from_pre_commit(self) -> None:
             if pre_commit_config.inform_how_to_use_on_migrate:
                 self.print_how_to_use()
 
-    def get_active_config_file_managers(self) -> set[KeyValueFileManager]:
+    def get_active_config_file_managers(self) -> set[KeyValueFileManager[object]]:
         """Get file managers for all active configuration files.
 
         Active configuration files are just those that we expect to use based on our
@@ -257,8 +257,8 @@ def _get_active_config_file_managers_from_resolution(
         self,
         resolution: ResolutionT,
         *,
-        file_manager_by_relative_path: dict[Path, KeyValueFileManager],
-    ) -> set[KeyValueFileManager]:
+        file_manager_by_relative_path: dict[Path, KeyValueFileManager[object]],
+    ) -> set[KeyValueFileManager[object]]:
         if resolution == "first":
             # N.B. keep this roughly in sync with the bespoke logic for pytest
             # since that logic is based on this logic.
@@ -334,7 +334,10 @@ def add_configs(self) -> None:
                     already_added = True
 
     def _add_config_item(
-        self, config_item: ConfigItem, *, file_managers: set[KeyValueFileManager]
+        self,
+        config_item: ConfigItem,
+        *,
+        file_managers: set[KeyValueFileManager[object]],
     ) -> bool:
         """Add a specific configuration item using specified file managers.
 
@@ -603,7 +606,7 @@ def _unconditional_update_bitbucket_steps(
             ):
                 remove_bitbucket_step_from_default(step)
 
-    def _get_select_keys(self, file_manager: KeyValueFileManager) -> list[str]:
+    def _get_select_keys(self, file_manager: KeyValueFileManager[object]) -> list[str]:
         """Get the configuration keys for selected rules.
 
         This is optional - tools that don't support rule selection can leave this
@@ -655,7 +658,7 @@ def select_rules(self, rules: list[Rule]) -> bool:
 
         return True
 
-    def _get_ignore_keys(self, file_manager: KeyValueFileManager) -> list[str]:
+    def _get_ignore_keys(self, file_manager: KeyValueFileManager[object]) -> list[str]:
         """Get the configuration keys for ignored rules.
 
         Args:

diff --git a/src/usethis/_tool/config.py b/src/usethis/_tool/config.py
@@ -47,7 +47,7 @@ class ConfigSpec(BaseModel):
     @classmethod
     def from_flat(
         cls,
-        file_managers: list[KeyValueFileManager],
+        file_managers: list[KeyValueFileManager[object]],
         resolution: ResolutionT,
         config_items: list[ConfigItem],
     ) -> Self:
@@ -146,7 +146,7 @@ def paths(self) -> set[Path]:
         return {(usethis_config.cpd() / path).resolve() for path in self.root}
 
 
-def ensure_managed_file_exists(file_manager: UsethisFileManager) -> None:
+def ensure_managed_file_exists(file_manager: UsethisFileManager[object]) -> None:
     """Ensure a file manager's managed file exists."""
     if isinstance(file_manager, PyprojectTOMLManager):
         ensure_pyproject_toml()

diff --git a/src/usethis/_tool/impl/base/deptry.py b/src/usethis/_tool/impl/base/deptry.py
@@ -69,7 +69,7 @@ def ignored_rules(self) -> list[Rule]:
 
         return rules
 
-    def _get_ignore_keys(self, file_manager: KeyValueFileManager) -> list[str]:
+    def _get_ignore_keys(self, file_manager: KeyValueFileManager[object]) -> list[str]:
         """Get the keys for the ignored rules in the given file manager."""
         if isinstance(file_manager, PyprojectTOMLManager):
             return ["tool", "deptry", "ignore"]

diff --git a/src/usethis/_tool/impl/base/pytest.py b/src/usethis/_tool/impl/base/pytest.py
@@ -134,7 +134,7 @@ def print_how_to_use(self) -> None:
         how_print("Add test functions with the format 'test_*()'.")
         how_print(f"Run '{self.how_to_use_cmd()}' to run the tests.")
 
-    def get_active_config_file_managers(self) -> set[KeyValueFileManager]:
+    def get_active_config_file_managers(self) -> set[KeyValueFileManager[object]]:
         # This is a variant of the "first" method
         config_spec = self.config_spec()
         if config_spec.resolution != "bespoke":

diff --git a/src/usethis/_tool/impl/base/ruff.py b/src/usethis/_tool/impl/base/ruff.py
@@ -445,7 +445,7 @@ def _are_pydocstyle_rules_selected(self) -> bool:
     def _is_pydocstyle_rule(rule: Rule) -> bool:
         return [d for d in rule if d.isalpha()] == ["D"]
 
-    def _get_select_keys(self, file_manager: KeyValueFileManager) -> list[str]:
+    def _get_select_keys(self, file_manager: KeyValueFileManager[object]) -> list[str]:
         """Get the keys for the selected rules in the given file manager."""
         if isinstance(file_manager, PyprojectTOMLManager):
             return ["tool", "ruff", "lint", "select"]
@@ -454,7 +454,7 @@ def _get_select_keys(self, file_manager: KeyValueFileManager) -> list[str]:
         else:
             return super()._get_select_keys(file_manager)
 
-    def _get_ignore_keys(self, file_manager: KeyValueFileManager) -> list[str]:
+    def _get_ignore_keys(self, file_manager: KeyValueFileManager[object]) -> list[str]:
         """Get the keys for the ignored rules in the given file manager."""
         if isinstance(file_manager, PyprojectTOMLManager):
             return ["tool", "ruff", "lint", "ignore"]
@@ -464,7 +464,7 @@ def _get_ignore_keys(self, file_manager: KeyValueFileManager) -> list[str]:
             return super()._get_ignore_keys(file_manager)
 
     def _get_per_file_ignore_keys(
-        self, file_manager: KeyValueFileManager, *, glob: str
+        self, file_manager: KeyValueFileManager[object], *, glob: str
     ) -> list[str]:
         """Get the keys for the per-file ignored rules in the given file manager."""
         if isinstance(file_manager, PyprojectTOMLManager):
@@ -478,7 +478,9 @@ def _get_per_file_ignore_keys(
             )
             raise NotImplementedError(msg)
 
-    def _get_docstyle_keys(self, file_manager: KeyValueFileManager) -> list[str]:
+    def _get_docstyle_keys(
+        self, file_manager: KeyValueFileManager[object]
+    ) -> list[str]:
         """Get the keys for the docstyle rules in the given file manager."""
         if isinstance(file_manager, PyprojectTOMLManager):
             return ["tool", "ruff", "lint", "pydocstyle", "convention"]

diff --git a/src/usethis/_tool/impl/spec/codespell.py b/src/usethis/_tool/impl/spec/codespell.py
@@ -32,7 +32,7 @@ def meta(self) -> ToolMeta:
             managed_files=[Path(".codespellrc")],
         )
 
-    def preferred_file_manager(self) -> KeyValueFileManager:
+    def preferred_file_manager(self) -> KeyValueFileManager[object]:
         if (usethis_config.cpd() / "pyproject.toml").exists():
             return PyprojectTOMLManager()
         return DotCodespellRCManager()

diff --git a/src/usethis/_tool/impl/spec/coverage_py.py b/src/usethis/_tool/impl/spec/coverage_py.py
@@ -21,7 +21,7 @@ def meta(self) -> ToolMeta:
             managed_files=[Path(".coveragerc"), Path(".coveragerc.toml")],
         )
 
-    def preferred_file_manager(self) -> KeyValueFileManager:
+    def preferred_file_manager(self) -> KeyValueFileManager[object]:
         if (usethis_config.cpd() / "pyproject.toml").exists():
             return PyprojectTOMLManager()
         return DotCoverageRCManager()
diff --git a/src/usethis/_tool/impl/spec/import_linter.py b/src/usethis/_tool/impl/spec/import_linter.py
@@ -50,7 +50,7 @@ def raw_cmd(self) -> str:
     def dev_deps(self, *, unconditional: bool = False) -> list[Dependency]:
         return [Dependency(name="import-linter")]
 
-    def preferred_file_manager(self) -> KeyValueFileManager:
+    def preferred_file_manager(self) -> KeyValueFileManager[object]:
         if (usethis_config.cpd() / "pyproject.toml").exists():
             return PyprojectTOMLManager()
         return DotImportLinterManager()
@@ -94,7 +94,9 @@ def _get_layered_architecture_by_module_by_root_package(
     def _get_resolution(self) -> ResolutionT:
         return "first"
 
-    def _get_file_manager_by_relative_path(self) -> dict[Path, KeyValueFileManager]:
+    def _get_file_manager_by_relative_path(
+        self,
+    ) -> dict[Path, KeyValueFileManager[object]]:
         return {
             Path("setup.cfg"): SetupCFGManager(),
             Path(".importlinter"): DotImportLinterManager(),

diff --git a/src/usethis/_tool/impl/spec/mkdocs.py b/src/usethis/_tool/impl/spec/mkdocs.py
@@ -28,7 +28,7 @@ def doc_deps(self, *, unconditional: bool = False) -> list[Dependency]:
 
         return deps
 
-    def preferred_file_manager(self) -> KeyValueFileManager:
+    def preferred_file_manager(self) -> KeyValueFileManager[object]:
         """If there is no currently active config file, this is the preferred one."""
         # Should set the mkdocs.yml file manager as the preferred one
         return MkDocsYMLManager()
diff --git a/src/usethis/_tool/impl/spec/pytest.py b/src/usethis/_tool/impl/spec/pytest.py
@@ -30,7 +30,7 @@ def meta(self) -> ToolMeta:
     def raw_cmd(self) -> str:
         return "pytest"
 
-    def preferred_file_manager(self) -> KeyValueFileManager:
+    def preferred_file_manager(self) -> KeyValueFileManager[object]:
         if (usethis_config.cpd() / "pyproject.toml").exists():
             return PyprojectTOMLManager()
         return PytestINIManager()
diff --git a/src/usethis/_tool/impl/spec/ruff.py b/src/usethis/_tool/impl/spec/ruff.py
@@ -25,7 +25,7 @@ def meta(self) -> ToolMeta:
     def dev_deps(self, *, unconditional: bool = False) -> list[Dependency]:
         return [Dependency(name="ruff")]
 
-    def preferred_file_manager(self) -> KeyValueFileManager:
+    def preferred_file_manager(self) -> KeyValueFileManager[object]:
         if (usethis_config.cpd() / "pyproject.toml").exists():
             return PyprojectTOMLManager()
         return RuffTOMLManager()
diff --git a/src/usethis/_tool/spec.py b/src/usethis/_tool/spec.py
@@ -71,7 +71,7 @@ def rule_config(self) -> RuleConfig:
         """
         return self.meta.rule_config
 
-    def preferred_file_manager(self) -> KeyValueFileManager:
+    def preferred_file_manager(self) -> KeyValueFileManager[object]:
         """If there is no currently active config file, this is the preferred one.
 
         This can vary dynamically, since often we will prefer to respect an existing