[RFC/WIP]: assert: use safeformat for display with -vv

[blueyed]

TODO:

• real plugin hook?
• should handle other places where safeformat is used also, via
  args/options to the hook then likely.
• test

Ref: #3962
Ref: #5933

[blueyed]

Keeping newlines can result in many lines:

testing/test_pdb.py:358: in test_meta_different_init_signture
    assert "set_trace" in sys._getframe().f_code.co_names
E   assert 'set_trace' in ('pdb',
E      'Pdb',
E      'PdbTest',
E      'sys',
E      '_getframe',
E      'f_code',
E      'co_names',
E      '_pytest.warning_types',
E      'PytestAssertRewriteWarning',
E      'warnings',
E      'warn_explicit',
E      '@pytest_ar',
E      '_call_reprcompare',
E      '_call_reprdisplay',
E      '@py_builtins',
E      'locals',
E      '_should_repr_global_name',
E      'AssertionError',
E      '_format_explanation',
E      'local',
E      'GLOBAL_PDB',
E      '_pdb2',
E      'stdout')
E    +  where ('pdb',
E        'Pdb',
E        'PdbTest',
E        'sys',
E        '_getframe',
E        'f_code',
E        'co_names',
E        '_pytest.warning_types',
E        'PytestAssertRewriteWarning',
E        'warnings',
E        'warn_explicit',
E        '@pytest_ar',
E        '_call_reprcompare',
E        '_call_reprdisplay',
E        '@py_builtins',
E        'locals',
E        '_should_repr_global_name',
E        'AssertionError',
E        '_format_explanation',
E        'local',
E        'GLOBAL_PDB',
E        '_pdb2',
E        'stdout') = <code object test_meta_different_init_signture at 0x7fcaa73a4b70, file "…/src/pdbpp/testing/test_pdb.py", line 328>.co_names
E    +    where <code object test_meta_different_init_signture at 0x7fcaa73a4b70, file "…/src/pdbpp/testing/test_pdb.py", line 328> = <frame at 0x562badb85620, file '…/src/pdbpp/testing/test_pdb.py', line 358, code test_meta_different_init_signture>.f_code
E    +      where <frame at 0x562badb85620, file '…/src/pdbpp/testing/test_pdb.py', line 358, code test_meta_different_init_signture> = <built-in function _getframe>()
E    +        where <built-in function _getframe> = sys._getframe

Alternatively we could bump the width to something very big, so that it wraps the automatically (hopefully), or replace newlines from pformat with spaces.

[blueyed]

Required to pass this test: https://github.com/pytest-dev/pytest/pull/2212/files#diff-14ad89cac128f1dd3aaa927c656035b3

[nicoddemus]

The change looks good, I would avoid adding a hook until we have real use cases for the hook other than the builtin implementation.

[blueyed]

The change looks good, I would avoid adding a hook until we have real use cases for the hook other than the builtin implementation.

Agreed.
could we have this now then already?
(given that no existing tests are failing we're kind of in the "good area" still)

[nicoddemus]

could we have this now then already?

Yep, just needs at least a test and CHANGELOG. 👍