feat: add python_dotted_filenames ini option

AUTHORS

@@ -527,3 +527,4 @@ Zachary OBrien
 Zhouxin Qiu
 Zoltán Máté
 Zsolt Cserna
+NIK-TIGER-BILL

changelog/14514.feature.rst

@@ -0,0 +1 @@
+Added ``python_dotted_filenames`` ini option to replace dots in test file names with underscores when computing module names, enabling pytest to collect tests from files like ``test.foo.py``.

src/_pytest/pathlib.py

@@ -505,6 +505,7 @@ def import_path(
     mode: str | ImportMode = ImportMode.prepend,
     root: Path,
     consider_namespace_packages: bool,
+    dotted_filenames: bool = False,
 ) -> ModuleType:
     """
     Import and return a module from the given path, which can be a file (a module) or
@@ -550,7 +551,9 @@ def import_path(
         # without touching sys.path.
         try:
             _, module_name = resolve_pkg_root_and_module_name(
-                path, consider_namespace_packages=consider_namespace_packages
+                path,
+                consider_namespace_packages=consider_namespace_packages,
+                dotted_filenames=dotted_filenames,
             )
         except CouldNotResolvePathError:
             pass
@@ -576,7 +579,9 @@ def import_path(
 
     try:
         pkg_root, module_name = resolve_pkg_root_and_module_name(
-            path, consider_namespace_packages=consider_namespace_packages
+            path,
+            consider_namespace_packages=consider_namespace_packages,
+            dotted_filenames=dotted_filenames,
         )
     except CouldNotResolvePathError:
         pkg_root, module_name = path.parent, path.stem
@@ -845,7 +850,10 @@ def resolve_package_path(path: Path) -> Path | None:
 
 
 def resolve_pkg_root_and_module_name(
-    path: Path, *, consider_namespace_packages: bool = False
+    path: Path,
+    *,
+    consider_namespace_packages: bool = False,
+    dotted_filenames: bool = False,
 ) -> tuple[Path, str]:
     """
     Return the path to the directory of the root package that contains the
@@ -874,14 +882,18 @@ def resolve_pkg_root_and_module_name(
     if consider_namespace_packages:
         start = pkg_root if pkg_root is not None else path.parent
         for candidate in (start, *start.parents):
-            module_name = compute_module_name(candidate, path)
+            module_name = compute_module_name(
+                candidate, path, dotted_filenames=dotted_filenames
+            )
             if module_name and is_importable(module_name, path):
                 # Point the pkg_root to the root of the namespace package.
                 pkg_root = candidate
                 break
 
     if pkg_root is not None:
-        module_name = compute_module_name(pkg_root, path)
+        module_name = compute_module_name(
+            pkg_root, path, dotted_filenames=dotted_filenames
+        )
         if module_name:
             return pkg_root, module_name
 
@@ -914,7 +926,9 @@ def is_importable(module_name: str, module_path: Path) -> bool:
         return spec_matches_module_path(spec, module_path)
 
 
-def compute_module_name(root: Path, module_path: Path) -> str | None:
+def compute_module_name(
+    root: Path, module_path: Path, *, dotted_filenames: bool = False
+) -> str | None:
     """Compute a module name based on a path and a root anchor."""
     try:
         path_without_suffix = module_path.with_suffix("")
@@ -931,6 +945,8 @@ def compute_module_name(root: Path, module_path: Path) -> str | None:
         return None
     if names[-1] == "__init__":
         names.pop()
+    if dotted_filenames:
+        names = [name.replace(".", "_") for name in names]
     return ".".join(names)
 
 

src/_pytest/python.py

@@ -117,6 +117,12 @@ def pytest_addoption(parser: Parser) -> None:
         default=None,
         help="Emit an error if non-unique parameter set IDs are detected",
     )
+    parser.addini(
+        "python_dotted_filenames",
+        type="bool",
+        default=False,
+        help="Replace dots in test file names with underscores when computing module names",
+    )
 
 
 def pytest_generate_tests(metafunc: Metafunc) -> None:
@@ -510,6 +516,7 @@ def importtestmodule(
             mode=importmode,
             root=config.rootpath,
             consider_namespace_packages=config.getini("consider_namespace_packages"),
+            dotted_filenames=config.getini("python_dotted_filenames"),
         )
     except SyntaxError as e:
         raise nodes.Collector.CollectError(

testing/test_pathlib.py

@@ -242,6 +242,45 @@ def test_messy_name(self, tmp_path: Path, ns_param: bool) -> None:
         module = import_path(path, root=tmp_path, consider_namespace_packages=ns_param)
         assert module.__name__ == "foo__init__"
 
+    def test_dotted_filename(self, tmp_path: Path, ns_param: bool) -> None:
+        """import_path handles dotted filenames when dotted_filenames=True."""
+        # Create a package so resolve_pkg_root_and_module_name works.
+        pkg = tmp_path / "pkg"
+        pkg.mkdir()
+        (pkg / "__init__.py").touch()
+        p = pkg / "test.bar.py"
+        p.touch()
+        mod = import_path(
+            p,
+            root=tmp_path,
+            mode=ImportMode.importlib,
+            consider_namespace_packages=ns_param,
+            dotted_filenames=True,
+        )
+        assert mod.__name__ == "pkg.test_bar"
+        # Without dotted_filenames, the dot is kept in the module name.
+        mod2 = import_path(
+            p,
+            root=tmp_path,
+            mode=ImportMode.importlib,
+            consider_namespace_packages=ns_param,
+            dotted_filenames=False,
+        )
+        assert mod2.__name__ == "pkg.test.bar"
+
+    def test_dotted_filename_ini(self, pytester: Pytester) -> None:
+        """python_dotted_filenames ini option replaces dots in test file names."""
+        pytester.makeini(
+            "[pytest]\npython_dotted_filenames = true\npython_files = test_*.py *.py\n"
+        )
+        pkg = pytester.path / "pkg"
+        pkg.mkdir()
+        (pkg / "__init__.py").write_text("")
+        (pkg / "test.bar.py").write_text("def test_foo(): pass\n")
+        result = pytester.runpytest("-v", "--import-mode=importlib")
+        result.assert_outcomes(passed=1)
+        result.stdout.fnmatch_lines(["*pkg/test.bar.py::test_foo PASSED*"])
+
     def test_dir(self, tmp_path: Path, ns_param: bool) -> None:
         p = tmp_path / "hello_123"
         p.mkdir()
@@ -1734,6 +1773,20 @@ def test_compute_module_name(tmp_path: Path) -> None:
         == "src.app.bar"
     )
 
+    # dotted_filenames replaces dots in file names with underscores.
+    assert (
+        compute_module_name(
+            tmp_path, tmp_path / "src/app/test.bar.py", dotted_filenames=True
+        )
+        == "src.app.test_bar"
+    )
+    assert (
+        compute_module_name(
+            tmp_path, tmp_path / "src/app/test.bar.py", dotted_filenames=False
+        )
+        == "src.app.test.bar"
+    )
+
 
 def validate_namespace_package(
     pytester: Pytester, paths: Sequence[Path], modules: Sequence[str]