config: consider empty .pytest.ini as config file

Fix #13849.

Author: bluetech

changelog/13849.bugfix.rst

@@ -0,0 +1,2 @@
+Hidden ``.pytest.ini`` files are now picked up as the config file even if empty.
+This was an inconsistency with non-hidden ``pytest.ini``.

src/_pytest/config/findpaths.py

@@ -68,7 +68,7 @@ def load_config_dict_from_file(
             }
         else:
             # "pytest.ini" files are always the source of configuration, even if empty.
-            if filepath.name == "pytest.ini":
+            if filepath.name in {"pytest.ini", ".pytest.ini"}:
                 return {}
 
     # '.cfg' files are considered if they contain a "[tool:pytest]" section.

testing/test_config.py

@@ -1826,13 +1826,16 @@ def test_with_ini(self, tmp_path: Path, name: str, contents: str) -> None:
         assert parsed_inipath == inipath
         assert ini_config["x"] == ConfigValue("10", origin="file")
 
-    @pytest.mark.parametrize("name", ["setup.cfg", "tox.ini"])
-    def test_pytestini_overrides_empty_other(self, tmp_path: Path, name: str) -> None:
-        inipath = tmp_path / "pytest.ini"
+    @pytest.mark.parametrize("pytest_ini", ["pytest.ini", ".pytest.ini"])
+    @pytest.mark.parametrize("other", ["setup.cfg", "tox.ini"])
+    def test_pytestini_overrides_empty_other(
+        self, tmp_path: Path, pytest_ini: str, other: str
+    ) -> None:
+        inipath = tmp_path / pytest_ini
         inipath.touch()
         a = tmp_path / "a"
         a.mkdir()
-        (a / name).touch()
+        (a / other).touch()
         rootpath, parsed_inipath, *_ = determine_setup(
             inifile=None,
             override_ini=None,

testing/test_findpaths.py

@@ -15,9 +15,10 @@
 
 
 class TestLoadConfigDictFromFile:
-    def test_empty_pytest_ini(self, tmp_path: Path) -> None:
+    @pytest.mark.parametrize("filename", ["pytest.ini", ".pytest.ini"])
+    def test_empty_pytest_ini(self, tmp_path: Path, filename: str) -> None:
         """pytest.ini files are always considered for configuration, even if empty"""
-        fn = tmp_path / "pytest.ini"
+        fn = tmp_path / filename
         fn.write_text("", encoding="utf-8")
         assert load_config_dict_from_file(fn) == {}