chore: stricter mypy (#2053)

* chore: improve mypy

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* chore(types): type functions in tests

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* chore(types): No partial types in tests

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

unit_test/linux_build_steps_test.py

@@ -4,12 +4,14 @@ import textwrap
 from pathlib import Path
 from pprint import pprint
 
+import pytest
+
 import cibuildwheel.linux
 from cibuildwheel.oci_container import OCIContainerEngineConfig
 from cibuildwheel.options import CommandLineArguments, Options
 
 
-def test_linux_container_split(tmp_path: Path, monkeypatch):
+def test_linux_container_split(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
     """
     Tests splitting linux builds by container image, container engine, and before_all
     """
@@ -53,13 +55,13 @@ def test_linux_container_split(tmp_path: Path, monkeypatch):
     build_steps = list(cibuildwheel.linux.get_build_steps(options, python_configurations))
 
     # helper functions to extract test info
-    def identifiers(step):
+    def identifiers(step: cibuildwheel.linux.BuildStep) -> list[str]:
         return [c.identifier for c in step.platform_configs]
 
-    def before_alls(step):
+    def before_alls(step: cibuildwheel.linux.BuildStep) -> list[str]:
         return [options.build_options(c.identifier).before_all for c in step.platform_configs]
 
-    def container_engines(step):
+    def container_engines(step: cibuildwheel.linux.BuildStep) -> list[OCIContainerEngineConfig]:
         return [options.build_options(c.identifier).container_engine for c in step.platform_configs]
 
     pprint(build_steps)