Fix unclosed scandir iterator in path_to_filesystem

Use os.scandir() as a context manager to ensure the iterator is
properly closed. This fixes ResourceWarning: unclosed scandir iterator
that occurs when the iterator is garbage collected without being closed.

Fixes #1972

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

radicale/tests/test_pathutils.py

@@ -0,0 +1,91 @@
+# This file is part of Radicale - CalDAV and CardDAV server
+# Copyright © 2025 Tobias Brox <tobias@tobix.eu>
+#
+# This library is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Radicale.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+Tests for pathutils module.
+
+"""
+
+import gc
+import os
+import tempfile
+
+import pytest
+
+from radicale import pathutils
+
+
+class TestPathToFilesystem:
+    """Tests for path_to_filesystem function."""
+
+    @pytest.mark.filterwarnings("error::ResourceWarning")
+    @pytest.mark.filterwarnings("error::pytest.PytestUnraisableExceptionWarning")
+    def test_scandir_iterator_closed(self) -> None:
+        """Verify that os.scandir iterator is properly closed.
+
+        This test catches ResourceWarning: unclosed scandir iterator
+        which occurs when os.scandir() is used without a context manager.
+        See: https://github.com/Kozea/Radicale/issues/1972
+
+        The ResourceWarning is emitted during garbage collection when an
+        unclosed scandir iterator is finalized. We use pytest.mark.filterwarnings
+        to convert both ResourceWarning and PytestUnraisableExceptionWarning
+        to errors.
+        """
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create a subdirectory so path_to_filesystem has something
+            # to scan (the scandir check is for case-insensitive filesystems)
+            subdir = os.path.join(tmpdir, "testdir")
+            os.makedirs(subdir)
+
+            # Call path_to_filesystem - if scandir iterator is not closed,
+            # a ResourceWarning will be emitted during garbage collection
+            result = pathutils.path_to_filesystem(tmpdir, "testdir")
+            assert result == subdir
+
+            # Force garbage collection to trigger any ResourceWarning
+            # from unclosed iterators
+            gc.collect()
+
+    def test_path_to_filesystem_basic(self) -> None:
+        """Test basic path_to_filesystem functionality."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Test empty path
+            result = pathutils.path_to_filesystem(tmpdir, "")
+            assert result == tmpdir
+
+            # Test single component
+            subdir = os.path.join(tmpdir, "test")
+            os.makedirs(subdir)
+            result = pathutils.path_to_filesystem(tmpdir, "test")
+            assert result == subdir
+
+            # Test nested path
+            nested = os.path.join(subdir, "nested")
+            os.makedirs(nested)
+            result = pathutils.path_to_filesystem(tmpdir, "test/nested")
+            assert result == nested
+
+    def test_unsafe_path_raises(self) -> None:
+        """Test that unsafe path components raise UnsafePathError."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Hidden files (starting with .) are not safe
+            with pytest.raises(pathutils.UnsafePathError):
+                pathutils.path_to_filesystem(tmpdir, ".hidden")
+
+            # Backup files (ending with ~) are not safe
+            with pytest.raises(pathutils.UnsafePathError):
+                pathutils.path_to_filesystem(tmpdir, "backup~")