borg2 create crashes if there are a lot of unchanged files

[ThomasWaldmann]

As reported by ender on IRC, borg 2.0.0b15:

AttributeError: 'NoneType' object has no attribute 'iteritems'

If reporting bugs, please include the following:

Traceback (most recent call last):
  File "borg/archiver/__init__.py", line 647, in main
  File "borg/archiver/__init__.py", line 541, in run
  File "borg/archiver/_common.py", line 169, in wrapper
  File "borg/archiver/create_cmd.py", line 268, in do_create
  File "borg/archiver/create_cmd.py", line 169, in create_inner
  File "borg/archiver/create_cmd.py", line 527, in _rec_walk
  File "borg/archiver/create_cmd.py", line 527, in _rec_walk
  File "borg/archiver/create_cmd.py", line 467, in _rec_walk
  File "borg/archiver/create_cmd.py", line 284, in _process_any
  File "borg/archive.py", line 1419, in process_file
  File "borg/archive.py", line 1180, in process_file_chunks
  File "borg/archive.py", line 1174, in chunk_processor
  File "borg/cache.py", line 884, in add_chunk
  File "borg/cache.py", line 902, in _maybe_write_chunks_cache
  File "borg/cache.py", line 715, in write_chunkindex_to_repo_cache
AttributeError: 'NoneType' object has no attribute 'iteritems'

Platform: Linux deepthought 6.14.0-rc6-20250411-00279-gc79cf4111930 #1 SMP PREEMPT_DYNAMIC Thu Apr 10 19:45:08 CEST 2025 x86_64
Linux: Unknown Linux
Borg: 2.0.0b15  Python: CPython 3.12.10 msgpack: 1.1.0 fuse: llfuse 1.5.1 [pyfuse3,llfuse]
PID: 11533  CWD: /root/scripts/backup
sys.argv: ['/opt/borg-dir/borg-linux-glibc236', '-v', '--iec', 'create', '--progress', '-s', '--compression=zstd,22', 'deepthought-NextCloud', '/pub/web/webapps/nextcloud', '/mnt/share/Misc/nextcloud_data', '/pub/backup/mysql.dump', '/mnt/share/Backup/pg']
SSH_ORIGINAL_COMMAND: None

[ThomasWaldmann]

This happens if borg create processes ONLY unchanged files for more than 10 minutes and thus does not need to demand-load the chunks index. Then it tries to save the not-yet-loaded chunks index to the repo and crashes.

Workaround

Guess a workaround could be to give it one changed file that it finds at beginning of borg create.

[ThomasWaldmann]

I fixed this in master branch, but reopening it for a while for better visibility to 2.0.0b15 users.