[chaley]

Originally Posted by kjdavies

@chaley, I just downloaded and installed 6.28 (Windows 10).

I tried to merge two titles via the GUI and I get an error message:

calibre, version 6.28.0
ERROR: Unhandled exception: <b>AttributeError</b>:'tuple' object has no attribute 'extend'

calibre 6.28  embedded-python: True
Windows-10-10.0.19045-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.19045')
Python 3.10.1
Windows: ('10', '10.0.19045', 'SP0', 'Multiprocessor Free')
Interface language: None
Successfully initialized third party plugins: Action Chains (1, 18, 12) && Babelio_db (0, 8, 3) && Baen (1, 1, 0) && Barnes & Noble (1, 5, 2) && CalibreSpy (1, 0, 92) && Category Tags (0, 2, 8) && Comicvine (0, 14, 1) && Consolidate All Library Metadata (2, 0, 46) && Count Pages (1, 13, 2) && Embed Comic Metadata (1, 6, 6) && Entities Manager (1, 0, 19) && Extract ISBN (1, 6, 0) && FanFicFare (4, 28, 0) && Fantastic Fiction (1, 6, 4) && Fantastic Fiction Adults (1, 3, 0) && FictionDB (1, 4, 1) && Find Duplicates (1, 10, 8) && Generate Cover (2, 3, 3) && Goodreads (1, 7, 9) && Highlights to Obsidian (1, 4, 0) && Job Spy (1, 0, 239) && Manage Series (1, 5, 1) && Mass Search-Replace (1, 7, 4) && Open With (1, 8, 1) && Quality Check (1, 13, 6) && Reading List (1, 15, 1) && Recipe Reader (1, 0, 1) && Smashwords Metadata (1, 0, 2) && View Manager (1, 10, 2) && all recipes Recipe Reader (1, 0, 2)
Traceback (most recent call last):
  File "calibre\gui2\actions\edit_metadata.py", line 676, in merge_books
  File "calibre\gui2\actions\edit_metadata.py", line 734, in merge_metadata
  File "calibre\db\cache.py", line 85, in call_func_with_lock
  File "calibre\db\cache.py", line 3260, in merge_book_metadata
AttributeError: 'tuple' object has no attribute 'extend'

This is a regression introduced when merge books became a calibre db API method. The exception happens when both the source and the destination of a multiple-value custom column (like tags) have values.

It is fixed in source.