fix: render gap.py invalid-AD debug log without raising TypeError (#220)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: bluetoothbot

src/bluetooth_data_tools/gap.py

@@ -203,9 +203,10 @@ def _uncached_parse_advertisement_bytes(
         offset += 1 + length
         if end > total_length or end - start <= 0:
             _LOGGER.debug(
-                "Invalid BLE GAP AD structure at offset %s: %s (%s)",
+                "Invalid BLE GAP AD structure at offset %s: %s (length=%s)",
                 offset,
                 gap_bytes,
+                length,
             )
             continue
         if gap_type_num == TYPE_SHORT_LOCAL_NAME and local_name is None:

tests/test_gap.py

@@ -563,6 +563,19 @@ def test_out_of_bounds_length():
     )
 
 
+def test_invalid_ad_debug_log_renders_without_error(caplog):
+    """Malformed AD must produce a renderable debug log (regression: format-string mismatch)."""
+    # length=5 (claims 4 payload bytes after the type byte) but only 2 follow.
+    # Unique payload so the lru_cache doesn't return a previous result.
+    data = b"\x05\x09\xab\xcd"
+    with caplog.at_level("DEBUG", logger="bluetooth_data_tools.gap"):
+        adv = parse_advertisement_data((data,))
+    assert adv.local_name is None
+    # Render every captured record — a format-string mismatch raises here.
+    messages = [r.getMessage() for r in caplog.records]
+    assert any("Invalid BLE GAP AD structure" in m for m in messages)
+
+
 def test_out_of_bounds_length_by_one():
     """Test out of bound length by one."""