fix(types): full strictness checking on mypy (#596)

* Add some missing generic arguments

* fix(types): add full strict checking

* fix(types): enable extra error checks

* Update .pre-commit-config.yaml

Co-authored-by: Robert Craigie <robert@craigie.dev>
Co-authored-by: Tom Fleet <tomfleet2018@gmail.com>

.pre-commit-config.yaml

@@ -63,11 +63,11 @@ repos:
         additional_dependencies: *flake8-dependencies
 
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v0.931
+    rev: v0.942
     hooks:
       - id: mypy
         files: ^nox/
-        args: [--show-error-codes]
+        args: []
         additional_dependencies:
           - types-jinja2
           - packaging

nox/_decorators.py

@@ -18,7 +18,7 @@
 import functools
 import inspect
 import types
-from typing import Any, Callable, Iterable
+from typing import Any, Callable, Iterable, TypeVar, cast
 
 from . import _typing
 
@@ -34,24 +34,27 @@ def __new__(
         return functools.wraps(func)(obj)
 
 
-def _copy_func(src: Callable, name: str | None = None) -> Callable:
+T = TypeVar("T", bound=Callable[..., Any])
+
+
+def _copy_func(src: T, name: str | None = None) -> T:
     dst = types.FunctionType(
         src.__code__,
-        src.__globals__,  # type: ignore[attr-defined]
+        src.__globals__,
         name=name or src.__name__,
-        argdefs=src.__defaults__,  # type: ignore[attr-defined]
-        closure=src.__closure__,  # type: ignore[attr-defined]
+        argdefs=src.__defaults__,
+        closure=src.__closure__,
     )
     dst.__dict__.update(copy.deepcopy(src.__dict__))
     dst = functools.update_wrapper(dst, src)
-    dst.__kwdefaults__ = src.__kwdefaults__  # type: ignore[attr-defined]
-    return dst
+    dst.__kwdefaults__ = src.__kwdefaults__
+    return cast(T, dst)
 
 
 class Func(FunctionDecorator):
     def __init__(
         self,
-        func: Callable,
+        func: Callable[..., Any],
         python: _typing.Python = None,
         reuse_venv: bool | None = None,
         name: str | None = None,

nox/_option_set.py

@@ -83,7 +83,11 @@ def __init__(
         noxfile: bool = False,
         merge_func: Callable[[Namespace, Namespace], Any] | None = None,
         finalizer_func: Callable[[Any, Namespace], Any] | None = None,
-        default: Any | Callable[[], Any] = None,
+        default: bool
+        | str
+        | None
+        | list[str]
+        | Callable[[], bool | str | None | list[str]] = None,
         hidden: bool = False,
         completer: Callable[..., list[str]] | None = None,
         **kwargs: Any,
@@ -101,7 +105,7 @@ def __init__(
         self._default = default
 
     @property
-    def default(self) -> bool | str | None:
+    def default(self) -> bool | str | None | list[str]:
         if callable(self._default):
             return self._default()
         return self._default

nox/_options.py

@@ -79,8 +79,8 @@ def _sessions_and_keywords_merge_func(
         noxfile_Args (_option_set.Namespace): The options specified in the
             Noxfile."""
     if not command_args.sessions and not command_args.keywords:
-        return getattr(noxfile_args, key)
-    return getattr(command_args, key)
+        return getattr(noxfile_args, key)  # type: ignore[no-any-return]
+    return getattr(command_args, key)  # type: ignore[no-any-return]
 
 
 def _default_venv_backend_merge_func(
@@ -123,7 +123,7 @@ def _force_venv_backend_merge_func(
         else:
             return "none"
     else:
-        return command_args.force_venv_backend or noxfile_args.force_venv_backend
+        return command_args.force_venv_backend or noxfile_args.force_venv_backend  # type: ignore[no-any-return]
 
 
 def _envdir_merge_func(

nox/_version.py

@@ -37,7 +37,7 @@ class InvalidVersionSpecifier(Exception):
 
 def get_nox_version() -> str:
     """Return the version of the installed Nox package."""
-    return metadata.version("nox")  # type: ignore[no-untyped-call]
+    return metadata.version("nox")  # type: ignore[no-untyped-call, no-any-return]
 
 
 def _parse_string_constant(node: ast.AST) -> str | None:  # pragma: no cover

nox/command.py

@@ -46,18 +46,18 @@ def which(program: str, paths: list[str] | None) -> str:
         full_path = py.path.local.sysfind(program, paths=paths)
 
     if full_path:
-        return full_path.strpath
+        return full_path.strpath  # type: ignore[no-any-return]
 
     full_path = py.path.local.sysfind(program)
 
     if full_path:
-        return full_path.strpath
+        return full_path.strpath  # type: ignore[no-any-return]
 
     logger.error(f"Program {program} not found.")
     raise CommandFailed(f"Program {program} not found")
 
 
-def _clean_env(env: dict | None) -> dict | None:
+def _clean_env(env: dict[str, str] | None) -> dict[str, str] | None:
     if env is None:
         return None
 
@@ -78,7 +78,7 @@ def _shlex_join(args: Sequence[str]) -> str:
 def run(
     args: Sequence[str],
     *,
-    env: dict | None = None,
+    env: dict[str, str] | None = None,
     silent: bool = False,
     paths: list[str] | None = None,
     success_codes: Iterable[int] | None = None,

nox/logger.py

@@ -47,7 +47,7 @@ def format(self, record: Any) -> str:
         return super().format(record)
 
 
-class NoxColoredFormatter(ColoredFormatter):
+class NoxColoredFormatter(ColoredFormatter):  # type: ignore[misc]
     def __init__(
         self,
         datefmt: Any = None,
@@ -70,7 +70,7 @@ def __init__(
     def format(self, record: Any) -> str:
         if record.levelname == "OUTPUT":
             return self._simple_fmt.format(record)
-        return super().format(record)
+        return super().format(record)  # type: ignore[no-any-return]
 
 
 class LoggerWithSuccessAndOutput(logging.getLoggerClass()):  # type: ignore[misc]

nox/manifest.py

@@ -16,7 +16,6 @@
 
 import argparse
 import ast
-import collections.abc
 import itertools
 from collections import OrderedDict
 from typing import Any, Iterable, Iterator, Mapping, Sequence
@@ -310,7 +309,7 @@ def notify(
         raise ValueError(f"Session {session} not found.")
 
 
-class KeywordLocals(collections.abc.Mapping):
+class KeywordLocals(Mapping[str, bool]):
     """Eval locals using keywords.
 
     When looking up a local variable the variable name is compared against

nox/popen.py

@@ -22,7 +22,7 @@
 
 
 def shutdown_process(
-    proc: subprocess.Popen,
+    proc: subprocess.Popen[bytes],
     interrupt_timeout: float | None,
     terminate_timeout: float | None,
 ) -> tuple[bytes, bytes]:
@@ -61,8 +61,8 @@ def popen(
     args: Sequence[str],
     env: Mapping[str, str] | None = None,
     silent: bool = False,
-    stdout: int | IO | None = None,
-    stderr: int | IO = subprocess.STDOUT,
+    stdout: int | IO[str] | None = None,
+    stderr: int | IO[str] = subprocess.STDOUT,
     interrupt_timeout: float | None = 0.3,
     terminate_timeout: float | None = 0.2,
 ) -> tuple[int, str]:

nox/sessions.py

@@ -216,7 +216,7 @@ def invoked_from(self) -> str:
         to the Noxfile's directory before running any sessions. This gives
         you the original working directory that Nox was invoked form.
         """
-        return self._runner.global_config.invoked_from
+        return self._runner.global_config.invoked_from  # type: ignore[no-any-return]
 
     def chdir(self, dir: str | os.PathLike[str]) -> _WorkingDirContext:
         """Change the current working directory.

nox/virtualenv.py

@@ -112,7 +112,7 @@ def locate_via_py(version: str) -> str | None:
     py_exe = py.path.local.sysfind("py")
     if py_exe is not None:
         try:
-            return py_exe.sysexec("-" + version, "-c", script).strip()
+            return py_exe.sysexec("-" + version, "-c", script).strip()  # type: ignore[no-any-return]
         except py.process.cmdexec.Error:
             return None
     return None

nox/workflow.py

@@ -42,7 +42,7 @@ def execute(
     """
     try:
         # Iterate over each task and run it.
-        return_value = None
+        return_value: Any = None
         for function_ in workflow:
             # Send the previous task's return value if there was one.
             args: list[Any] = []

pyproject.toml

@@ -34,20 +34,10 @@ testpaths = [
 [tool.mypy]
 files = ["nox"]
 python_version = "3.7"
-warn_unused_configs = true
-disallow_any_generics = false
-disallow_subclassing_any = false
-disallow_untyped_calls = true
-disallow_untyped_defs = true
-disallow_incomplete_defs = true
-check_untyped_defs = true
-disallow_untyped_decorators = true
-no_implicit_optional = true
-warn_redundant_casts = true
-warn_unused_ignores = true
-warn_return_any = false
-no_implicit_reexport = true
-strict_equality = true
+show_error_codes = true
+strict = true
+warn_unreachable = true
+enable_error_code = ["ignore-without-code", "redundant-expr", "truthy-bool"]
 
 [[tool.mypy.overrides]]
 module = [ "argcomplete", "colorlog.*", "py", "tox.*" ]