Fix test for pip 26.1 uninstall behavior

pip 26.1 (pypa/pip#13725) tracks the entire __pycache__ directory for
removal instead of individual .pyc files, which breaks pip's empty
parent directory cleanup. Empty leftover dirs (pip/, _distutils_hack/)
now remain after uninstall. Filter empty directory trees out of the
post-uninstall assertion.

Author: gaborbernat

docs/changelog/u.bugfix.rst docs/changelog/3132.bugfix.rstdocs/changelog/u.bugfix.rst renamed to docs/changelog/3132.bugfix.rst

@@ -122,7 +122,12 @@ def test_seed_link_via_app_data(tmp_path, coverage_env, current_fastest, copies,
         purelib = result.creator.purelib
         patch_files = {purelib / f"{'_virtualenv'}.{i}" for i in ("py", "pyc", "pth")}
         patch_files.add(purelib / "__pycache__")
-        post_run = set(site_package.iterdir()) - patch_files
+
+        # pip 26.1+ leaves empty parent directories on uninstall (pypa/pip#13725)
+        def _has_files(path: Path) -> bool:
+            return path.is_file() or (path.is_dir() and any(_has_files(child) for child in path.iterdir()))
+
+        post_run = {p for p in set(site_package.iterdir()) - patch_files if _has_files(p)}
         assert not post_run, "\n".join(str(i) for i in post_run)