fix: closes #11343's [attr-defined] type errors

src/_pytest/compat.py

@@ -313,16 +313,26 @@ def safe_isclass(obj: object) -> bool:
         return False
 
 
-def get_user_id() -> int | None:
-    """Return the current user id, or None if we cannot get it reliably on the current platform."""
-    # win32 does not have a getuid() function.
-    # On Emscripten, getuid() is a stub that always returns 0.
-    if sys.platform in ("win32", "emscripten"):
+def get_user_id(*, UNRELIABLE: int = -1) -> int | None:
+    """Return the current user id, or None if we cannot get it reliably on
+    the current platform.
+
+    :param UNRELIABLE:
+        The platform-specific constant which indicates that the retrieved uid
+        is unreliable. The default value, -1, is a common unreliability
+        indicator on UNIX-like systems.
+    :return: The user id or None
+    """
+    # mypy follows the version and platform checking expectation of PEP 484:
+    # https://mypy.readthedocs.io/en/stable/common_issues.html?highlight=platform#python-version-and-system-platform-checks
+    # Containment checks are too complex for mypy v1.5.0 and cause failure.
+    if sys.platform == "win32" or sys.platform == "emscripten":
+        # win32 does not have a getuid() function.
+        # Emscripten has a return 0 stub.
         return None
-    # getuid shouldn't fail, but cpython defines such a case.
-    # Let's hope for the best.
-    uid = os.getuid()
-    return uid if uid != -1 else None
+    else:
+        uid = os.getuid()
+        return uid if uid != UNRELIABLE else None
 
 
 # Perform exhaustiveness checking.

testing/test_parseopt.py

@@ -291,7 +291,8 @@ def test_multiple_metavar_help(self, parser: parseopt.Parser) -> None:
 
 def test_argcomplete(pytester: Pytester, monkeypatch: MonkeyPatch) -> None:
     try:
-        encoding = locale.getencoding()  # New in Python 3.11, ignores utf-8 mode
+        # New in Python 3.11, ignores utf-8 mode
+        encoding = locale.getencoding()  # type: ignore[attr-defined]
     except AttributeError:
         encoding = locale.getpreferredencoding(False)
     try: