New submission from Finite State Machine :
The following Python script:
from dataclasses import dataclass
@dataclass
class A:
mro: object
x: object
Results in the following unexpected exception:
Traceback (most recent call last):
File "/Users/dsuffling/.pyenv/versions/3.10.0/lib/python3.10/runpy.py",
line 196, in _run_module_as_main
return _run_code(code, main_globals, None,
File "/Users/dsuffling/.pyenv/versions/3.10.0/lib/python3.10/runpy.py",
line 86, in _run_code
exec(code, run_globals)
File "/Users/dsuffling/names/junk.py", line 6, in
class A:
File
"/Users/dsuffling/.pyenv/versions/3.10.0/lib/python3.10/dataclasses.py", line
1178, in dataclass
return wrap(cls)
File
"/Users/dsuffling/.pyenv/versions/3.10.0/lib/python3.10/dataclasses.py", line
1169, in wrap
return _process_class(cls, init, repr, eq, order, unsafe_hash,
File
"/Users/dsuffling/.pyenv/versions/3.10.0/lib/python3.10/dataclasses.py", line
1019, in _process_class
_init_fn(all_init_fields,
File
"/Users/dsuffling/.pyenv/versions/3.10.0/lib/python3.10/dataclasses.py", line
540, in _init_fn
raise TypeError(f'non-default argument {f.name!r} '
TypeError: non-default argument 'x' follows default argument
The name of the first attribute ('mro') is critical; without it the problem
does not occur.
It appears that 'mro' is somehow interacting with the 'mro' attribute of the
'type' object.
This issue has been verified to occur with CPython 3.10.0.
--
components: Library (Lib)
messages: 404378
nosy: finite-state-machine
priority: normal
severity: normal
status: open
title: field "mro" behaves strangely in dataclass
type: behavior
versions: Python 3.10
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<https://bugs.python.org/issue45531>
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