Fix collection of short paths on Windows (#11936)

Passing a short path in the command line was causing the matchparts check to fail, because ``Path(short_path) != Path(long_path)``.

Using ``os.path.samefile`` as fallback ensures the comparsion works on Windows when comparing short/long paths.

Fix #11895

changelog/11895.bugfix.rst

@@ -0,0 +1 @@
+Fix collection on Windows where initial paths contain the short version of a path (for example ``c:\PROGRA~1\tests``).

src/_pytest/main.py

@@ -906,6 +906,10 @@ class Session(nodes.Collector):
                     # Path part e.g. `/a/b/` in `/a/b/test_file.py::TestIt::test_it`.
                     if isinstance(matchparts[0], Path):
                         is_match = node.path == matchparts[0]
+                        if sys.platform == "win32" and not is_match:
+                            # In case the file paths do not match, fallback to samefile() to
+                            # account for short-paths on Windows (#11895).
+                            is_match = os.path.samefile(node.path, matchparts[0])
                     # Name part e.g. `TestIt` in `/a/b/test_file.py::TestIt::test_it`.
                     else:
                         # TODO: Remove parametrized workaround once collection structure contains

testing/test_collection.py

@@ -4,9 +4,11 @@ from pathlib import Path
 import pprint
 import shutil
 import sys
+import tempfile
 import textwrap
 from typing import List
 
+from _pytest.assertion.util import running_on_ci
 from _pytest.config import ExitCode
 from _pytest.fixtures import FixtureRequest
 from _pytest.main import _in_venv
@@ -1759,3 +1761,29 @@ def test_does_not_crash_on_recursive_symlink(pytester: Pytester) -> None:
 
     assert result.ret == ExitCode.OK
     assert result.parseoutcomes() == {"passed": 1}
+
+
+@pytest.mark.skipif(not sys.platform.startswith("win"), reason="Windows only")
+def test_collect_short_file_windows(pytester: Pytester) -> None:
+    """Reproducer for #11895: short paths not colleced on Windows."""
+    short_path = tempfile.mkdtemp()
+    if "~" not in short_path:  # pragma: no cover
+        if running_on_ci():
+            # On CI, we are expecting that under the current GitHub actions configuration,
+            # tempfile.mkdtemp() is producing short paths, so we want to fail to prevent
+            # this from silently changing without us noticing.
+            pytest.fail(
+                f"tempfile.mkdtemp() failed to produce a short path on CI: {short_path}"
+            )
+        else:
+            # We want to skip failing this test locally in this situation because
+            # depending on the local configuration tempfile.mkdtemp() might not produce a short path:
+            # For example, user might have configured %TEMP% exactly to avoid generating short paths.
+            pytest.skip(
+                f"tempfile.mkdtemp() failed to produce a short path: {short_path}, skipping"
+            )
+
+    test_file = Path(short_path).joinpath("test_collect_short_file_windows.py")
+    test_file.write_text("def test(): pass", encoding="UTF-8")
+    result = pytester.runpytest(short_path)
+    assert result.parseoutcomes() == {"passed": 1}