Reliance on dataclasses throws errors in pip for Python3.9 #30
Description
Hello. I have used this library a handful of times over the years and it has been helpful to me.
Recently, however, on Python 3.9 I have seen failing builds due to the dependence on dataclasses. After installing ecological, all further pip commands throw errors like this:
Traceback (most recent call last):
File "/install/bin/pip", line 5, in <module>
from pip._internal.cli.main import main
File "/install/lib/python3.9/site-packages/pip/_internal/cli/main.py", line 9, in <module>
from pip._internal.cli.autocompletion import autocomplete
File "/install/lib/python3.9/site-packages/pip/_internal/cli/autocompletion.py", line 10, in <module>
from pip._internal.cli.main_parser import create_main_parser
File "/install/lib/python3.9/site-packages/pip/_internal/cli/main_parser.py", line 8, in <module>
from pip._internal.cli import cmdoptions
File "/install/lib/python3.9/site-packages/pip/_internal/cli/cmdoptions.py", line 23, in <module>
from pip._internal.cli.parser import ConfigOptionParser
File "/install/lib/python3.9/site-packages/pip/_internal/cli/parser.py", line 12, in <module>
from pip._internal.configuration import Configuration, ConfigurationError
File "/install/lib/python3.9/site-packages/pip/_internal/configuration.py", line 20, in <module>
from pip._internal.exceptions import (
File "/install/lib/python3.9/site-packages/pip/_internal/exceptions.py", line 14, in <module>
from pip._vendor.rich.console import Console, ConsoleOptions, RenderResult
File "/install/lib/python3.9/site-packages/pip/_vendor/rich/console.py", line 55, in <module>
from .pretty import Pretty, is_expandable
File "/install/lib/python3.9/site-packages/pip/_vendor/rich/pretty.py", line 366, in <module>
class Node:
File "/install/lib/python3.9/site-packages/dataclasses.py", line 958, in dataclass
return wrap(_cls)
File "/install/lib/python3.9/site-packages/dataclasses.py", line 950, in wrap
return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
File "/install/lib/python3.9/site-packages/dataclasses.py", line 800, in _process_class
cls_fields = [_get_field(cls, name, type)
File "/install/lib/python3.9/site-packages/dataclasses.py", line 800, in <listcomp>
cls_fields = [_get_field(cls, name, type)
File "/install/lib/python3.9/site-packages/dataclasses.py", line 659, in _get_field
if (_is_classvar(a_type, typing)
File "/install/lib/python3.9/site-packages/dataclasses.py", line 550, in _is_classvar
return type(a_type) is typing._ClassVar
AttributeError: module 'typing' has no attribute '_ClassVar'When ecological is removed as a dependency (or copied and built without dataclasses) the error goes away.
My request is to change the pyproject.toml for this project to stop supporting python 3.6 and remove the dependency on dataclasses:
[tool.poetry.dependencies]
python = "^3.7"There is a precedent for other Python libraries recently dropping support for Python3.6.
Alternatively, I know that with a setup.py, it's possible to specify a dependency like dataclasses only if using an earlier Python version. For instance, in a setup.py, the following would work:
install_requires=["dataclasses>=0.7;python_version<'3.7'"]I believe that the pyproject.toml for this project may be modified in the following way to achieve this:
dataclasses = {version = "0.6", markers = "python_version < '3.7'"}