[CI] Fix typecheck in GHA (#22)

Use Python 3.10 in Cirrus CI for typecheck

.cirrus.yml

@@ -61,7 +61,7 @@ typecheck_task:
   name: typecheck (Linux - 3.10)
   only_if: $TYPE_CHECKING == 'true'
   clone_script: *clone
-  container: {image: "python:3.9-bullseye"}  # most recent => better type support
+  container: {image: "python:3.10-bullseye"}  # most recent => better type support
   pip_cache: *pip-cache
   mypy_cache:
     folder: .mypy_cache

setup.cfg

@@ -70,6 +70,10 @@ testing =
     pytest
     pytest-cov
 
+typecheck =
+    mypy
+    importlib-resources
+
 [options.entry_points]
 # Add here console scripts like:
 console_scripts =

src/validate_pyproject/api.py

@@ -36,10 +36,10 @@
 
 
 try:  # pragma: no cover
-    if sys.version_info[:2] < (3, 7):
+    if sys.version_info[:2] < (3, 7) or TYPE_CHECKING:  # See #22
         from importlib_resources import files
     else:
-        from importlib.resources import files  # type: ignore[attr-defined]
+        from importlib.resources import files
 
     def read_text(package: Union[str, ModuleType], resource) -> str:
         return files(package).joinpath(resource).read_text(encoding="utf-8")

tox.ini

@@ -40,8 +40,7 @@ passenv =
     # ^ ensure colors
 extras =
     all
-deps =
-    mypy
+    typecheck
 commands =
     python -m mypy {posargs:src}