fix: handle Unicode normalization in save_dict for umlauts (#728) (#729)

tests/unit/test_dicts.py

@@ -0,0 +1,40 @@
+# SPDX-FileCopyrightText: © Sebastian Thomschke and contributors
+# SPDX-License-Identifier: AGPL-3.0-or-later
+# SPDX-ArtifactOfProjectHomePage: https://github.com/Second-Hand-Friends/kleinanzeigen-bot/
+"""Tests for the dicts utility module."""
+import unicodedata
+from pathlib import Path
+
+
+def test_save_dict_normalizes_unicode_paths(tmp_path:Path) -> None:
+    """Test that save_dict normalizes paths to NFC for cross-platform consistency (issue #728).
+
+    Directories are created with NFC normalization (via sanitize_folder_name).
+    This test verifies save_dict's defensive normalization handles edge cases where
+    an NFD path is passed (e.g., "ä" as "a" + combining diacritic vs single character).
+    It should normalize to NFC and use the existing NFC directory.
+    """
+    from kleinanzeigen_bot.utils import dicts  # noqa: PLC0415
+
+    # Create directory with NFC normalization (as sanitize_folder_name does)
+    title_nfc = unicodedata.normalize("NFC", "KitchenAid Zuhälter - nie benutzt")
+    nfc_dir = tmp_path / f"ad_12345_{title_nfc}"
+    nfc_dir.mkdir(parents = True)
+
+    # Call save_dict with NFD path (different normalization)
+    title_nfd = unicodedata.normalize("NFD", title_nfc)
+    assert title_nfc != title_nfd, "NFC and NFD should be different strings"
+
+    nfd_path = tmp_path / f"ad_12345_{title_nfd}" / "ad_12345.yaml"
+    dicts.save_dict(str(nfd_path), {"test": "data", "title": title_nfc})
+
+    # Verify file was saved successfully
+    nfc_files = list(nfc_dir.glob("*.yaml"))
+    assert len(nfc_files) == 1, "Should have exactly one file in NFC directory"
+    assert nfc_files[0].name == "ad_12345.yaml"
+
+    # On macOS/APFS, the filesystem normalizes both NFC and NFD to the same directory
+    # On Linux ext4, NFC normalization in save_dict ensures it uses the existing directory
+    # Either way, we should have exactly one YAML file total (no duplicates)
+    all_yaml_files = list(tmp_path.rglob("*.yaml"))
+    assert len(all_yaml_files) == 1, f"Expected exactly 1 YAML file total, found {len(all_yaml_files)}: {all_yaml_files}"