Fix ensure_empty_dir leaving directory symlinks behind

src/pyproject_api/_util.py

@@ -11,7 +11,7 @@ def ensure_empty_dir(path: Path) -> None:
     if path.exists():
         if path.is_dir():
             for sub_path in path.iterdir():
-                if sub_path.is_dir():
+                if sub_path.is_dir() and not sub_path.is_symlink():
                     rmtree(sub_path, ignore_errors=True)
                 else:
                     sub_path.unlink()

tests/test_util_regression.py

@@ -0,0 +1,23 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from pyproject_api._util import ensure_empty_dir
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+
+def test_ensure_empty_dir_on_path_symlink_to_dir(tmp_path: Path) -> None:
+    """A symlink pointing to a directory must be removed, not followed."""
+    target = tmp_path / "target"
+    target.mkdir()
+    (target / "c").write_text("")
+    work = tmp_path / "work"
+    work.mkdir()
+    link = work / "link"
+    link.symlink_to(target, target_is_directory=True)
+    ensure_empty_dir(work)
+    assert list(work.iterdir()) == []
+    # the symlink target itself must not be traversed and deleted
+    assert list(target.iterdir()) == [target / "c"]