Fix conftest fixture scoping when testpaths points outside rootdir

changelog/14004.bugfix.rst

@@ -0,0 +1,5 @@
+Fixed conftest.py fixture scoping when ``testpaths`` points outside ``rootdir``.
+
+Nodeids for paths outside ``rootdir`` are now computed more meaningfully:
+paths in site-packages use a ``site://`` prefix, nearby paths use relative
+paths with ``..`` components, and far-away paths use absolute paths.

src/_pytest/fixtures.py

@@ -1629,23 +1629,29 @@ def pytest_plugin_registered(self, plugin: _PluggyPlugin, plugin_name: str) -> N
             # case-insensitive systems (Windows) and other normalization issues
             # (issue #11816).
             conftestpath = absolutepath(plugin_name)
-            try:
-                nodeid = str(conftestpath.parent.relative_to(self.config.rootpath))
-            except ValueError:
-                nodeid = ""
-            if nodeid == ".":
-                nodeid = ""
-            if os.sep != nodes.SEP:
-                nodeid = nodeid.replace(os.sep, nodes.SEP)
+            # initial_paths not available yet at plugin registration time,
+            # so we skip that step and fall back to bestrelpath
+            nodeid = nodes.compute_nodeid_prefix_for_path(
+                path=conftestpath.parent,
+                rootpath=self.config.rootpath,
+                invocation_dir=self.config.invocation_params.dir,
+            )
         else:
             nodeid = None
 
         self.parsefactories(plugin, nodeid)
 
     def _getautousenames(self, node: nodes.Node) -> Iterator[str]:
         """Return the names of autouse fixtures applicable to node."""
+        seen_nodeids: set[str] = set()
         for parentnode in node.listchain():
-            basenames = self._nodeid_autousenames.get(parentnode.nodeid)
+            nodeid = parentnode.nodeid
+            # Avoid yielding duplicates when multiple nodes share the same nodeid
+            # (e.g., Session and root Directory both have nodeid "").
+            if nodeid in seen_nodeids:
+                continue
+            seen_nodeids.add(nodeid)
+            basenames = self._nodeid_autousenames.get(nodeid)
             if basenames:
                 yield from basenames
 

src/_pytest/nodes.py

@@ -38,6 +38,7 @@
 from _pytest.mark.structures import NodeKeywords
 from _pytest.outcomes import fail
 from _pytest.pathlib import absolutepath
+from _pytest.pathlib import bestrelpath
 from _pytest.stash import Stash
 from _pytest.warning_types import PytestWarning
 
@@ -557,6 +558,121 @@ def _check_initialpaths_for_relpath(
     return None
 
 
+def _get_site_packages_dirs() -> frozenset[Path]:
+    """Get all site-packages directories as resolved absolute paths."""
+    import site
+
+    dirs: set[Path] = set()
+    # Standard site-packages
+    for sp in site.getsitepackages():
+        try:
+            dirs.add(Path(sp).resolve())
+        except OSError:
+            pass
+    # User site-packages
+    user_site = site.getusersitepackages()
+    if user_site:
+        try:
+            dirs.add(Path(user_site).resolve())
+        except OSError:
+            pass
+    return frozenset(dirs)
+
+
+# Cache site-packages dirs since they don't change during a run.
+_SITE_PACKAGES_DIRS: frozenset[Path] | None = None
+
+
+def _get_cached_site_packages_dirs() -> frozenset[Path]:
+    """Get cached site-packages directories."""
+    global _SITE_PACKAGES_DIRS
+    if _SITE_PACKAGES_DIRS is None:
+        _SITE_PACKAGES_DIRS = _get_site_packages_dirs()
+    return _SITE_PACKAGES_DIRS
+
+
+def _path_in_site_packages(
+    path: Path,
+    site_packages: frozenset[Path] | None = None,
+) -> tuple[Path, Path] | None:
+    """Check if path is inside a site-packages directory.
+
+    :param path: The path to check.
+    :param site_packages: Optional set of site-packages directories to check against.
+        If None, uses the cached system site-packages directories.
+    Returns (site_packages_dir, relative_path) if found, None otherwise.
+    """
+    if site_packages is None:
+        site_packages = _get_cached_site_packages_dirs()
+    try:
+        resolved = path.resolve()
+    except OSError:
+        return None
+
+    for sp in site_packages:
+        try:
+            rel = resolved.relative_to(sp)
+            return (sp, rel)
+        except ValueError:
+            continue
+    return None
+
+
+def compute_nodeid_prefix_for_path(
+    path: Path,
+    rootpath: Path,
+    invocation_dir: Path,
+    site_packages: frozenset[Path] | None = None,
+) -> str:
+    """Compute a nodeid prefix for a filesystem path.
+
+    The nodeid prefix is computed based on the path's relationship to:
+    1. rootpath - if relative, use simple relative path
+    2. site-packages - use "site://<package>/<path>" prefix
+    3. invocation_dir - if close by, use relative path with ".." components
+    4. Otherwise, use absolute path
+
+    :param path: The path to compute a nodeid prefix for.
+    :param rootpath: The pytest root path.
+    :param invocation_dir: The directory from which pytest was invoked.
+    :param site_packages: Optional set of site-packages directories. If None,
+        uses the cached system site-packages directories.
+
+    The returned string uses forward slashes as separators regardless of OS.
+    """
+    # 1. Try relative to rootpath (simplest case)
+    try:
+        rel = path.relative_to(rootpath)
+        result = str(rel)
+        if result == ".":
+            return ""
+        return result.replace(os.sep, SEP)
+    except ValueError:
+        pass
+
+    # 2. Check if path is in site-packages
+    site_info = _path_in_site_packages(path, site_packages)
+    if site_info is not None:
+        _sp_dir, rel_path = site_info
+        result = f"site://{rel_path}"
+        return result.replace(os.sep, SEP)
+
+    # 3. Try relative to invocation_dir if "close by" (i.e., not too many ".." components)
+    rel_from_invocation = bestrelpath(invocation_dir, path)
+    # Count the number of ".." components - if it's reasonable, use the relative path
+    # Also check total path length to avoid overly long relative paths
+    parts = Path(rel_from_invocation).parts
+    up_count = sum(1 for p in parts if p == "..")
+    # Only use relative path if:
+    # - At most 2 ".." components (close to invocation dir)
+    # - bestrelpath actually produced a relative path (not the absolute path unchanged)
+    if up_count <= 2 and rel_from_invocation != str(path):
+        return rel_from_invocation.replace(os.sep, SEP)
+
+    # 4. Fall back to absolute path
+    return str(path).replace(os.sep, SEP)
+
+
 class FSCollector(Collector, abc.ABC):
     """Base class for filesystem collectors."""
 
@@ -597,13 +713,11 @@ def __init__(
             session = parent.session
 
         if nodeid is None:
-            try:
-                nodeid = str(self.path.relative_to(session.config.rootpath))
-            except ValueError:
-                nodeid = _check_initialpaths_for_relpath(session._initialpaths, path)
-
-            if nodeid and os.sep != SEP:
-                nodeid = nodeid.replace(os.sep, SEP)
+            nodeid = compute_nodeid_prefix_for_path(
+                path=path,
+                rootpath=session.config.rootpath,
+                invocation_dir=session.config.invocation_params.dir,
+            )
 
         super().__init__(
             name=name,

testing/test_nodes.py

@@ -138,3 +138,137 @@ def test_show_wrong_path(private_dir):
     )
     result = pytester.runpytest()
     result.stdout.fnmatch_lines([str(p) + ":*: AssertionError", "*1 failed in *"])
+
+
+class TestNodeidPrefixComputation:
+    """Tests for nodeid prefix computation for paths outside rootdir."""
+
+    def test_path_in_site_packages_found(self, tmp_path: Path) -> None:
+        """Test _path_in_site_packages finds paths inside site-packages."""
+        fake_site_packages = tmp_path / "site-packages"
+        fake_site_packages.mkdir()
+        pkg_path = fake_site_packages / "mypackage" / "tests" / "test_foo.py"
+        pkg_path.parent.mkdir(parents=True)
+        pkg_path.touch()
+
+        site_packages = frozenset([fake_site_packages])
+        result = nodes._path_in_site_packages(pkg_path, site_packages)
+
+        assert result is not None
+        sp_dir, rel_path = result
+        assert sp_dir == fake_site_packages
+        assert rel_path == Path("mypackage/tests/test_foo.py")
+
+    def test_path_in_site_packages_not_found(self, tmp_path: Path) -> None:
+        """Test _path_in_site_packages returns None for paths outside site-packages."""
+        fake_site_packages = tmp_path / "site-packages"
+        fake_site_packages.mkdir()
+        other_path = tmp_path / "other" / "test_foo.py"
+        other_path.parent.mkdir(parents=True)
+        other_path.touch()
+
+        site_packages = frozenset([fake_site_packages])
+        result = nodes._path_in_site_packages(other_path, site_packages)
+
+        assert result is None
+
+    def test_compute_nodeid_inside_rootpath(self, tmp_path: Path) -> None:
+        """Test nodeid computation for paths inside rootpath."""
+        rootpath = tmp_path / "project"
+        rootpath.mkdir()
+        test_file = rootpath / "tests" / "test_foo.py"
+        test_file.parent.mkdir(parents=True)
+        test_file.touch()
+
+        result = nodes.compute_nodeid_prefix_for_path(
+            path=test_file,
+            rootpath=rootpath,
+            invocation_dir=rootpath,
+            site_packages=frozenset(),
+        )
+
+        assert result == "tests/test_foo.py"
+
+    def test_compute_nodeid_outside_rootpath(self, tmp_path: Path) -> None:
+        """Test nodeid computation for paths outside rootpath uses bestrelpath."""
+        rootpath = tmp_path / "project"
+        rootpath.mkdir()
+        tests_dir = tmp_path / "tests"
+        tests_dir.mkdir()
+        test_file = tests_dir / "test_foo.py"
+        test_file.touch()
+
+        result = nodes.compute_nodeid_prefix_for_path(
+            path=test_file,
+            rootpath=rootpath,
+            invocation_dir=rootpath,
+            site_packages=frozenset(),
+        )
+
+        # Uses bestrelpath since outside rootpath
+        assert result == "../tests/test_foo.py"
+
+    def test_compute_nodeid_in_site_packages(self, tmp_path: Path) -> None:
+        """Test nodeid computation for paths in site-packages uses site:// prefix."""
+        rootpath = tmp_path / "project"
+        rootpath.mkdir()
+        fake_site_packages = tmp_path / "site-packages"
+        fake_site_packages.mkdir()
+        pkg_test = fake_site_packages / "mypackage" / "tests" / "test_foo.py"
+        pkg_test.parent.mkdir(parents=True)
+        pkg_test.touch()
+
+        result = nodes.compute_nodeid_prefix_for_path(
+            path=pkg_test,
+            rootpath=rootpath,
+            invocation_dir=rootpath,
+            site_packages=frozenset([fake_site_packages]),
+        )
+
+        assert result == "site://mypackage/tests/test_foo.py"
+
+    def test_compute_nodeid_nearby_relative(self, tmp_path: Path) -> None:
+        """Test nodeid computation for nearby paths uses relative path."""
+        rootpath = tmp_path / "project"
+        rootpath.mkdir()
+        sibling = tmp_path / "sibling" / "tests" / "test_foo.py"
+        sibling.parent.mkdir(parents=True)
+        sibling.touch()
+
+        result = nodes.compute_nodeid_prefix_for_path(
+            path=sibling,
+            rootpath=rootpath,
+            invocation_dir=rootpath,
+        )
+
+        assert result == "../sibling/tests/test_foo.py"
+
+    def test_compute_nodeid_far_away_absolute(self, tmp_path: Path) -> None:
+        """Test nodeid computation for far-away paths uses absolute path."""
+        rootpath = tmp_path / "deep" / "nested" / "project"
+        rootpath.mkdir(parents=True)
+        far_away = tmp_path / "other" / "location" / "tests" / "test_foo.py"
+        far_away.parent.mkdir(parents=True)
+        far_away.touch()
+
+        result = nodes.compute_nodeid_prefix_for_path(
+            path=far_away,
+            rootpath=rootpath,
+            invocation_dir=rootpath,
+        )
+
+        # Should use absolute path since it's more than 2 levels up
+        assert result == str(far_away)
+
+    def test_compute_nodeid_rootpath_itself(self, tmp_path: Path) -> None:
+        """Test nodeid computation for rootpath itself returns empty string."""
+        rootpath = tmp_path / "project"
+        rootpath.mkdir()
+
+        result = nodes.compute_nodeid_prefix_for_path(
+            path=rootpath,
+            rootpath=rootpath,
+            invocation_dir=rootpath,
+        )
+
+        assert result == ""