Error on cyclic import from package hidden in a function

Open
#2,418 1 comment 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
compilers

Research direction

Start by running the reproducer linked in the issue with the shown mypy command, then inspect how package/a.py, package/b.py, and package/init.py are analyzed for cyclic imports and deferred function imports. Compare the package import with the direct package.b import; done means the valid package form no longer produces the reported attribute and undefined-name errors.

Written by the indexing model from the issue text.

Description

bug false-positive priority-1-normal topic-import-cycles

I think that mypy incorrectly reports an error. Full steps to reproduce are at https://github.com/lopuhin/mypy-lang-issue-1, but basically, the issue is this: say we have a package package:

package
├── __init__.py
├── a.py
├── b.py
└── test.py

package/a.py has a class that has an import hidden in a function:

class A(object):
    def do(self):
        from package import do_b      # this gives an error
        # from package.b import do_b  # this works
        return do_b(self)

package/b.py defines that do_b function and has an import from package.a in order to have a valid type declaration:

from package.a import A

def do_b(a):
    # type: (A) -> str
    return 'foo'

package/__init__.py exports do_b from b:

from .b import do_b

And package/test.py is just to check that there is no error on the python level:

from package.a import A

a = A()
print(a.do())

Now, the command mypy --silent-imports --check-untyped-defs package gives the following error:

package/a.py: note: In function "do":
package/a.py:3: error: Module 'package' has no attribute 'do_b'
package/a.py:5: error: Name 'do_b' is not defined

But if we import from package.b directly in package/a.py, the error goes away.

Dominant language
Python
Stars
20.6k
Forks
3.3k
Avg merge
1d 18h
Merged PRs (30d)
54

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from python/mypy

All issues in python/mypy

Similar issues

More Python issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.