python3.5.[01]: Union[Pattern, str] raises an error

[asottile]

Need to make sure this gets quoted instead of left unquoted:

>>> Union[AnyStr, str]
typing.Union[~AnyStr, str]
>>> Union[str, Pattern]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.5/typing.py", line 534, in __getitem__
    dict(self.__dict__), parameters, _root=True)
  File "/usr/local/lib/python3.5/typing.py", line 491, in __new__
    for t2 in all_params - {t1} if not isinstance(t2, TypeVar)):
  File "/usr/local/lib/python3.5/typing.py", line 491, in <genexpr>
    for t2 in all_params - {t1} if not isinstance(t2, TypeVar)):
TypeError: issubclass() arg 1 must be a class

[asottile]

The hint is to add a visit_Subscript to here:

flake8-typing-imports/flake8_typing_imports.py

Line 440 in 292b2d5

class Visitor(ast.NodeVisitor):

And then report the error in the flake8 plugin below

Probably need to check for Pattern exactly, there may be other types that have problems as well

The nice thing about suggesting quoting is it won't show up in the ast because they're just strings!

[atugushev]

Seems like only affects Pattern and Match.

Probably need to check for Pattern exactly, there may be other types that have problems as well

Should typing.Pattern (as ast.Attribute, not ast.Name) be checked as well? For cases like:

def foo(bar: typings.Union[typings.Pattern, str])

[asottile]

yeah probably handle both typing.Pattern and Pattern -- the visitor already records the from import. if you're looking for prior art, pyupgrade does similar things for six imports

[atugushev]

Thanks for the hint!

[atugushev]

@asottile

Could you help me with an error text? I came up with:

1. TYP003 Union[Pattern, ...] or Union[Match, ...] is broken in <3.5.2
2. TYP003 Union[Pattern, Match, ...] is broken in <3.5.2
3. TYP003 Union[Pattern, Match, ...] is broken in <3.5.2, consider quoting type annotation
4. TYP003 Union[Match, ...] or Union[Pattern, ...] must be quoted in <3.5.2

[asottile]

available in 1.5.0!