Python 3.11 is pickier about mutable dataclass fields

[jamesjer]

The Fedora project is building all of its python packages with an alpha version of python 3.11, to try to identify problems and fix them prior to the actual 3.11 release. The sphinxcontrib-bibtex package is failing to build, as can be seen in this bug report. The issue seems to be that python has gotten pickier about ensuring that dataclass fields are not initialized with a mutable value. A sample error:

WARNING: autodoc: failed to import module 'bibtex.bibfile' from module 'sphinxcontrib'; the following exception was raised:
Traceback (most recent call last):
  File "/usr/lib64/python3.11/contextlib.py", line 155, in __exit__
    self.gen.throw(typ, value, traceback)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/sphinx/util/logging.py", line 276, in skip_warningiserror
    yield
    ^^^^^
  File "/usr/lib/python3.11/site-packages/sphinx/ext/autodoc/importer.py", line 70, in import_module
    return importlib.import_module(modname)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen importlib._bootstrap>", line 1206, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1178, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1149, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 690, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 915, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/builddir/build/BUILDROOT/python-sphinxcontrib-bibtex-2.4.1-2.fc36.x86_64/usr/lib/python3.11/site-packages/sphinxcontrib/bibtex/__init__.py", line 9, in <module>
    from .domain import BibtexDomain
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/builddir/build/BUILDROOT/python-sphinxcontrib-bibtex-2.4.1-2.fc36.x86_64/usr/lib/python3.11/site-packages/sphinxcontrib/bibtex/domain.py", line 44, in <module>
    from .style.referencing import (
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/builddir/build/BUILDROOT/python-sphinxcontrib-bibtex-2.4.1-2.fc36.x86_64/usr/lib/python3.11/site-packages/sphinxcontrib/bibtex/style/referencing/__init__.py", line 121, in <module>
    @dataclasses.dataclass
     ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/dataclasses.py", line 1187, in dataclass
    return wrap(cls)
           ^^^^^^^^^
  File "/usr/lib64/python3.11/dataclasses.py", line 1178, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/dataclasses.py", line 958, in _process_class
    cls_fields.append(_get_field(cls, name, type, kw_only))
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.11/dataclasses.py", line 815, in _get_field
    raise ValueError(f'mutable default {type(f.default)} for field '
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: mutable default <class 'pybtex.richtext.Text'> for field other is not allowed: use default_factory

This affects dataclass field initializations in the following files:

• doc/usage.rst
• src/sphinxcontrib/bibtex/style/referencing/init.py
• src/sphinxcontrib/bibtex/style/referencing/author_year.py
• src/sphinxcontrib/bibtex/style/referencing/basic_author_year.py
• src/sphinxcontrib/bibtex/style/referencing/basic_foot.py
• src/sphinxcontrib/bibtex/style/referencing/basic_label.py
• src/sphinxcontrib/bibtex/style/referencing/basic_super.py
• src/sphinxcontrib/bibtex/style/referencing/extra_author.py
• src/sphinxcontrib/bibtex/style/referencing/extra_label.py
• src/sphinxcontrib/bibtex/style/referencing/extra_year.py
• src/sphinxcontrib/bibtex/style/referencing/foot.py
• src/sphinxcontrib/bibtex/style/referencing/label.py
• src/sphinxcontrib/bibtex/style/referencing/super_.py
• test/roots/test-citation_style_round_brackets/conf.py
• test/test_citation.py
• test/test_footcite.py

[jamesjer]

I have taken a stab at addressing this:

https://src.fedoraproject.org/rpms/python-sphinxcontrib-bibtex/blob/rawhide/f/python-sphinxcontrib-bibtex-default-factory.patch

I don't know if that is an acceptable approach for you. If so, I can open a PR.

[mcmtroffaes]

Many thanks for reporting and for the base work on this. Patch looks ok besides some small issues; I'll push a similar patch shortly.

[kloczek]

Is it possible to make new release with those ffixes?

[mcmtroffaes]

Sure.

[kloczek]

Tahnk you 😃

[mcmtroffaes]

With pleasure!