Run type checks only against packaged *.py files

- for tests/ and the noxfile.py, type annotations are not strictly
  enforced any more
  + this simplifies the way test cases and nox sessions are written
  + for many pytest fixtures, no types are available via a public API
- put fixtures inside the classes the corresponding test cases are
  grouped in

noxfile.py

@@ -3,7 +3,6 @@
 import contextlib
 import os
 import tempfile
-from typing import Any, Generator
 
 import nox
 from nox.sessions import Session
@@ -14,11 +13,14 @@ MAIN_PYTHON = '3.8'
 # Keep the project is forward compatible.
 NEXT_PYTHON = '3.9'
 
+# Path to the *.py files to be packaged.
+PACKAGE_SOURCE_LOCATION = 'src/'
+
 # Path to the test suite.
 PYTEST_LOCATION = 'tests/'
 
-# Paths with *.py files.
+# Paths with all *.py files.
-SRC_LOCATIONS = 'noxfile.py', 'src/', PYTEST_LOCATION
+SRC_LOCATIONS = 'noxfile.py', PACKAGE_SOURCE_LOCATION, PYTEST_LOCATION
 
 
 # Use a unified .cache/ folder for all tools.
@@ -38,7 +40,7 @@ nox.options.sessions = (
 
 
 @nox.session(name='format', python=MAIN_PYTHON)
-def format_(session: Session) -> None:
+def format_(session):
     """Format source files with autoflake, black, and isort.
 
     If no extra arguments are provided, all source files are formatted.
@@ -68,7 +70,7 @@ def format_(session: Session) -> None:
 
 
 @nox.session(python=MAIN_PYTHON)
-def lint(session: Session) -> None:
+def lint(session):
     """Lint source files with flake8, mypy, and pylint.
 
     If no extra arguments are provided, all source files are linted.
@@ -93,8 +95,15 @@ def lint(session: Session) -> None:
     with _isort_fix(session):  # TODO (isort): Remove after upgrading
         session.run('isort', '--version')
         session.run('isort', '--check-only', *locations)
+    # For mypy, only lint *.py files to be packaged.
+    mypy_locations = [
+        path for path in locations if path.startswith(PACKAGE_SOURCE_LOCATION)
+    ]
+    if mypy_locations:
         session.run('mypy', '--version')
-    session.run('mypy', *locations)
+        session.run('mypy', *mypy_locations)
+    else:
+        session.log('No paths to be checked with mypy')
     # Ignore errors where pylint cannot import a third-party package due its
     # being run in an isolated environment. For the same reason, pylint is
     # also not able to determine the correct order of imports.
@@ -109,7 +118,7 @@ def lint(session: Session) -> None:
 
 
 @nox.session(python=[MAIN_PYTHON, NEXT_PYTHON])
-def test(session: Session) -> None:
+def test(session):
     """Test the code base.
 
     Runs the unit and integration tests (written with pytest).
@@ -148,7 +157,7 @@ def test(session: Session) -> None:
 
 
 @nox.session(name='pre-commit', python=MAIN_PYTHON, venv_backend='none')
-def pre_commit(session: Session) -> None:
+def pre_commit(session):
     """Source files must be well-formed before they enter git.
 
     Intended to be run as a pre-commit hook.
@@ -165,7 +174,7 @@ def pre_commit(session: Session) -> None:
 
 
 @nox.session(name='pre-merge', python=MAIN_PYTHON)
-def pre_merge(session: Session) -> None:
+def pre_merge(session):
     """The test suite must pass before merges are made.
 
     Intended to be run either as a pre-merge or pre-push hook.
@@ -188,7 +197,7 @@ def pre_merge(session: Session) -> None:
     test(session)
 
 
-def _begin(session: Session) -> None:
+def _begin(session):
     """Show generic info about a session."""
     if session.posargs:
         # Part of the hack in pre_merge() to "drop" the extra arguments.
@@ -205,9 +214,7 @@ def _begin(session: Session) -> None:
     print(os.getcwd())  # noqa:WPS421
 
 
-def _install_packages(
+def _install_packages(session: Session, *packages_or_pip_args: str, **kwargs) -> None:
-    session: Session, *packages_or_pip_args: str, **kwargs: Any,
-) -> None:
     """Install packages respecting the poetry.lock file.
 
     This function wraps nox.sessions.Session.install() such that it installs
@@ -251,7 +258,7 @@ def _install_packages(
 # TODO (isort): Remove this fix after
 # upgrading to isort ^5.2.2 in pyproject.toml.
 @contextlib.contextmanager
-def _isort_fix(session: Session) -> Generator:
+def _isort_fix(session):
     """Temporarily upgrade to isort 5.2.2."""
     session.install('isort==5.2.2')
     try:

setup.cfg

@@ -96,6 +96,8 @@ extend-ignore =
 
 per-file-ignores =
     noxfile.py:
+        # Type annotations are not strictly enforced.
+        ANN0, ANN2,
         # TODO (isort): Check if still too many module members.
         WPS202,
         # TODO (isort): Remove after simplifying the nox session "lint".
@@ -103,6 +105,8 @@ per-file-ignores =
         # No overuse of string constants (e.g., '--version').
         WPS226,
     tests/*.py:
+        # Type annotations are not strictly enforced.
+        ANN0, ANN2,
         # `assert` statements are ok in the test suite.
         S101,
         # Shadowing outer scopes occurs naturally with mocks.
@@ -177,7 +181,7 @@ single_line_exclusions = typing
 [mypy]
 cache_dir = .cache/mypy
 
-[mypy-nox.*,packaging.*,pytest,_pytest.*]
+[mypy-nox.*,packaging,pytest]
 ignore_missing_imports = true
 
 

tests/test_console.py

@@ -2,19 +2,11 @@
 
 import click
 import pytest
-from _pytest.capture import CaptureFixture  # noqa:WPS436
-from _pytest.monkeypatch import MonkeyPatch  # noqa:WPS436
 from click import testing as click_testing
 
 from urban_meal_delivery import console
 
 
-@pytest.fixture
-def ctx() -> click.Context:
-    """Context around the console.main Command."""
-    return click.Context(console.main)
-
-
 class TestShowVersion:
     """Test console.show_version().
 
@@ -29,7 +21,12 @@ class TestShowVersion:
 
     # pylint:disable=no-self-use
 
-    def test_no_version(self, capsys: CaptureFixture, ctx: click.Context) -> None:
+    @pytest.fixture
+    def ctx(self) -> click.Context:
+        """Context around the console.main Command."""
+        return click.Context(console.main)
+
+    def test_no_version(self, capsys, ctx):
         """The the early exit branch without any output."""
         console.show_version(ctx, _param='discarded', value=False)
 
@@ -37,9 +34,7 @@ class TestShowVersion:
 
         assert captured.out == ''
 
-    def test_final_version(
+    def test_final_version(self, capsys, ctx, monkeypatch):
-        self, capsys: CaptureFixture, ctx: click.Context, monkeypatch: MonkeyPatch,
-    ) -> None:
         """For final versions, NO "development" warning is emitted."""
         version = '1.2.3'
         monkeypatch.setattr(console.urban_meal_delivery, '__version__', version)
@@ -51,9 +46,7 @@ class TestShowVersion:
 
         assert captured.out.endswith(f', version {version}\n')
 
-    def test_develop_version(
+    def test_develop_version(self, capsys, ctx, monkeypatch):
-        self, capsys: CaptureFixture, ctx: click.Context, monkeypatch: MonkeyPatch,
-    ) -> None:
         """For develop versions, a warning thereof is emitted."""
         version = '1.2.3.dev0'
         monkeypatch.setattr(console.urban_meal_delivery, '__version__', version)
@@ -66,12 +59,6 @@ class TestShowVersion:
         assert captured.out.strip().endswith(f', version {version} (development)')
 
 
-@pytest.fixture
-def cli() -> click_testing.CliRunner:
-    """Initialize Click's CLI Test Runner."""
-    return click_testing.CliRunner()
-
-
 class TestCLI:
     """Test the `umd` CLI utility.
 
@@ -81,8 +68,13 @@ class TestCLI:
 
     # pylint:disable=no-self-use
 
+    @pytest.fixture
+    def cli(self) -> click_testing.CliRunner:
+        """Initialize Click's CLI Test Runner."""
+        return click_testing.CliRunner()
+
     @pytest.mark.no_cover
-    def test_no_options(self, cli: click_testing.CliRunner) -> None:
+    def test_no_options(self, cli):
         """Exit with 0 status code and no output if run without options."""
         result = cli.invoke(console.main)
 
@@ -94,12 +86,8 @@ class TestCLI:
     version_options = ('--version', '-V')
 
     @pytest.mark.no_cover
-    @pytest.mark.parametrize(
+    @pytest.mark.parametrize('option', version_options)
-        'option', version_options,
+    def test_final_version(self, cli, monkeypatch, option):
-    )
-    def test_final_version(
-        self, cli: click_testing.CliRunner, monkeypatch: MonkeyPatch, option: str,
-    ) -> None:
         """For final versions, NO "development" warning is emitted."""
         version = '1.2.3'
         monkeypatch.setattr(console.urban_meal_delivery, '__version__', version)
@@ -110,12 +98,8 @@ class TestCLI:
         assert result.output.strip().endswith(f', version {version}')
 
     @pytest.mark.no_cover
-    @pytest.mark.parametrize(
+    @pytest.mark.parametrize('option', version_options)
-        'option', version_options,
+    def test_develop_version(self, cli, monkeypatch, option):
-    )
-    def test_develop_version(
-        self, cli: click_testing.CliRunner, monkeypatch: MonkeyPatch, option: str,
-    ) -> None:
         """For develop versions, a warning thereof is emitted."""
         version = '1.2.3.dev0'
         monkeypatch.setattr(console.urban_meal_delivery, '__version__', version)

tests/test_version.py

@@ -13,35 +13,33 @@ import re
 
 import pytest
 from packaging import version as pkg_version
-from packaging.version import Version
 
 import urban_meal_delivery
 
 
-@pytest.fixture
-def parsed_version() -> str:
-    """The packaged version."""
-    return pkg_version.Version(urban_meal_delivery.__version__)  # noqa:WPS609
-
-
 class TestPEP404Compliance:
     """Packaged version identifier is PEP440 compliant."""
 
     # pylint:disable=no-self-use
 
-    def test_parsed_version_has_no_epoch(self, parsed_version: Version) -> None:
+    @pytest.fixture
+    def parsed_version(self) -> str:
+        """The packaged version."""
+        return pkg_version.Version(urban_meal_delivery.__version__)  # noqa:WPS609
+
+    def test_parsed_version_has_no_epoch(self, parsed_version):
         """PEP440 compliant subset of semantic versioning: no epoch."""
         assert parsed_version.epoch == 0
 
-    def test_parsed_version_is_non_local(self, parsed_version: Version) -> None:
+    def test_parsed_version_is_non_local(self, parsed_version):
         """PEP440 compliant subset of semantic versioning: no local version."""
         assert parsed_version.local is None
 
-    def test_parsed_version_is_no_post_release(self, parsed_version: Version) -> None:
+    def test_parsed_version_is_no_post_release(self, parsed_version):
         """PEP440 compliant subset of semantic versioning: no post releases."""
         assert parsed_version.is_postrelease is False
 
-    def test_parsed_version_is_all_public(self, parsed_version: Version) -> None:
+    def test_parsed_version_is_all_public(self, parsed_version):
         """PEP440 compliant subset of semantic versioning: all public parts."""
         assert parsed_version.public == urban_meal_delivery.__version__  # noqa:WPS609
 
@@ -55,7 +53,7 @@ class TestSemanticVersioning:
         r'^(0|([1-9]\d*))\.(0|([1-9]\d*))\.(0|([1-9]\d*))(\.dev(0|([1-9]\d*)))?$',
     )
 
-    def test_version_is_semantic(self) -> None:
+    def test_version_is_semantic(self):
         """Packaged version follows semantic versioning."""
         result = self.version_pattern.fullmatch(
             urban_meal_delivery.__version__,  # noqa:WPS609
@@ -79,7 +77,7 @@ class TestSemanticVersioning:
             '1.2.3.dev10',
         ],
     )
-    def test_valid_semantic_versioning(self, version: str) -> None:
+    def test_valid_semantic_versioning(self, version):
         """Versions follow the x.y.z or x.y.z.devN format."""
         result = self.version_pattern.fullmatch(version)
 
@@ -109,7 +107,7 @@ class TestSemanticVersioning:
             '1.2..3',
         ],
     )
-    def test_invalid_semantic_versioning(self, version: str) -> None:
+    def test_invalid_semantic_versioning(self, version):
         """Versions follow the x.y.z or x.y.z.devN format."""
         result = self.version_pattern.fullmatch(version)