Error on cyclic import from package hidden in a function

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Issue 类型
缺陷
描述清晰度
基本清楚
活跃度
停滞
技术栈
python
领域
compilers

调研方向

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.

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描述

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.

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