Conditional expression in "with" statement inferred as 'object', lacking __enter__ and __exit__ #5512
Description
from tempfile import TemporaryDirectory, TemporaryFile
import sys
use_file = 'directory' not in sys.argv
with (TemporaryFile() if use_file else TemporaryDirectory()) as thing:
print(thing)
Mypy infers the type of the conditional expression as object rather than Union[IO,TemporaryDirectory]
$ mypy multi_with.py
multi_with.py:6: error: "object" has no attribute "__enter__"
multi_with.py:6: error: "object" has no attribute "__exit__"
Explicitly typing the result of the conditional expression makes the error messages go away:
named_intermediate: Union[IO, TemporaryDirectory] = (TemporaryFile() if use_file else TemporaryDirectory())
with named_intermediate as thing:
print(thing)
I observe this in both mypy versions I tried: 0.600 and 0.620
These past issues and pull requests look relevant:
#3487 Type of conditional expression is join instead of union
#5041 Fix type of conditional statement to Union and not Join.
#5095 Don't always infer unions for conditional expressions