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Too strict behavior with --ignore-missing-imports #5226
Description
I think the --ignore-missing-imports currently behaves a bit inconsistently. If I have an existing directory with only an empty __init__.py, then running mypy with --ignore-missing-imports gives this:
import whatever.works
import existing.nonexisting
x = whatever.works.f() # No errors, as expected
y = existing.nonexisting.g() # Module has no attribute "nonexisting"At the same time both these work (in the same program, otherwise the second fails):
from whatever import works # no errors
from existing import nonexisting # no errorsI think the first example should work as well, since all non-existing modules should be replaced with a dummy Any (and apparently it looks easy to fix, unless this is intentional behavior for some reasons).
EDIT: see #5226 (comment)
Reacted by Emma Smith
Activity
gvanrossum commentedon Jun 17, 2018
ilevkivskyi commentedon Jun 17, 2018
Maybe. But what is the value of that error "Module has no attribute ..."?
ilevkivskyi commentedon Jun 17, 2018
Correction:
from existing import nonexistingalso fails. It however doesn't fail, if there is animport existing.nonexistingelsewhere.gvanrossum commentedon Jun 18, 2018
For me the deciding difference is whether it could reference something other than a module.
import existing.nonexistinghas to refer to a module, so--ignore-missing-importsapplies. Butfrom existing import nonexistingcould refer to a class, function or variable defined inexistingand as such it is not covered by--ignore-missing-imports. The presence ofimport existing.nonexistingelsewhere implies that it refers to a submodule, so then the flag applies.So I don't necessarily believe that "fixing" this will make things better -- it will just trade false positives for false negatives.
ilevkivskyi commentedon Jun 18, 2018
So do you prefer false positives? I prefer false negatives. Also as Jukka mentioned in the PR some users may be surprised that refactoring
import a.bintofrom a import bturns it into an error.gvanrossum commentedon Jun 18, 2018
[-]Inconsistency in --ignore-missing-imports[/-][+]Too strict behavior with --ignore-missing-imports[/+]ilevkivskyi commentedon Jun 18, 2018
OK, I updated the title.
Make --ignore-missing-imports less strict (#5228)