Make yaml file writes safer (#59384)

tests/util/test_file.py

@@ -0,0 +1,65 @@
+"""Test Home Assistant file utility functions."""
+import os
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+from homeassistant.util.file import WriteError, write_utf8_file
+
+
+def test_write_utf8_file_private(tmpdir):
+    """Test files can be written as 0o600 or 0o644."""
+    test_dir = tmpdir.mkdir("files")
+    test_file = Path(test_dir / "test.json")
+
+    write_utf8_file(test_file, '{"some":"data"}', False)
+    with open(test_file) as fh:
+        assert fh.read() == '{"some":"data"}'
+    assert os.stat(test_file).st_mode & 0o777 == 0o644
+
+    write_utf8_file(test_file, '{"some":"data"}', True)
+    with open(test_file) as fh:
+        assert fh.read() == '{"some":"data"}'
+    assert os.stat(test_file).st_mode & 0o777 == 0o600
+
+
+def test_write_utf8_file_fails_at_creation(tmpdir):
+    """Test that failed creation of the temp file does not create an empty file."""
+    test_dir = tmpdir.mkdir("files")
+    test_file = Path(test_dir / "test.json")
+
+    with pytest.raises(WriteError), patch(
+        "homeassistant.util.file.tempfile.NamedTemporaryFile", side_effect=OSError
+    ):
+        write_utf8_file(test_file, '{"some":"data"}', False)
+
+    assert not os.path.exists(test_file)
+
+
+def test_write_utf8_file_fails_at_rename(tmpdir, caplog):
+    """Test that if rename fails not not remove, we do not log the failed cleanup."""
+    test_dir = tmpdir.mkdir("files")
+    test_file = Path(test_dir / "test.json")
+
+    with pytest.raises(WriteError), patch(
+        "homeassistant.util.file.os.replace", side_effect=OSError
+    ):
+        write_utf8_file(test_file, '{"some":"data"}', False)
+
+    assert not os.path.exists(test_file)
+
+    assert "File replacement cleanup failed" not in caplog.text
+
+
+def test_write_utf8_file_fails_at_rename_and_remove(tmpdir, caplog):
+    """Test that if rename and remove both fail, we log the failed cleanup."""
+    test_dir = tmpdir.mkdir("files")
+    test_file = Path(test_dir / "test.json")
+
+    with pytest.raises(WriteError), patch(
+        "homeassistant.util.file.os.remove", side_effect=OSError
+    ), patch("homeassistant.util.file.os.replace", side_effect=OSError):
+        write_utf8_file(test_file, '{"some":"data"}', False)
+
+    assert "File replacement cleanup failed" in caplog.text