False-positive E1101 (no-member) for writable file-like object

[tucked]

Steps to reproduce

"""sscce.py"""

class Context:
    def __enter__(self):
        return self
    def __exit__(self, type_, exc, traceback):
        return False

class Iterable(Context):
    def __iter__(self):
        return self
    def __next__(self):
        return self
    def write(self, x):
        print(x)

class Foo(Iterable):
    pass

with Foo() as foo:
    foo.write('something')

Note: Like #3233, this was found while using paramiko:

        with self._sftp.open(local_path, mode) as local_file:
            local_file.write(contents)  # triggers on write

local_file is a paramiko.SFTPFile which inherits from paramiko.BufferedFile which inherits paramiko.util.ClosingContextManager.

Current behavior

sscce.py:21:4: E1101: Instance of 'Context' has no 'write' member (no-member)

Expected behavior

(no error)

pylint --version output

pylint 2.4.3
astroid 2.3.3
Python 3.6.8 (default, Oct  7 2019, 12:59:55)
[GCC 8.3.0]

[simonvanderveldt]

Can confirm, just ran into this as well in our case we're using paramiko.Transport like this

with paramiko.Transport(...) as transport:
        transport.connect(...)

And we get this linting error

app/lambda_function.py:98:8: E1101: Instance of 'ClosingContextManager' has no 'connect' member (no-member)

I'm not even sure how it gets to the ClosingContextManager since the Transport class itself has a connect() member
https://github.com/paramiko/paramiko/blob/2.6.0/paramiko/transport.py#L1222

[PCManticore]

Thanks for the example, folks, I can confirm the bug.

[actionless]

i wonder, if it's the same issue or not:

from typing import Any, List, Optional


NOT_FOUND_ATOM = object()


class AnnotatedDataType():

    def _key_not_exists(self, key):
        return getattr(self, key, NOT_FOUND_ATOM) is NOT_FOUND_ATOM

    def __init__(self, **kwargs) -> None:
        for key, value in kwargs.items():
            setattr(self, key, value)
        for key in self.__annotations__:  # pylint: disable=no-member
            if self._key_not_exists(key):
                raise TypeError(
                    f"'{self.__class__.__name__}' does "
                    f"not have required attribute '{key}' set"
                )

    def __setattr__(self, key: str, value: Any) -> None:
        if (
                not getattr(self, "__annotations__", None) or
                self.__annotations__.get(key, NOT_FOUND_ATOM) is NOT_FOUND_ATOM  # pylint: disable=no-member
        ) and self._key_not_exists(key):
            raise TypeError(
                f"'{self.__class__.__name__}' does "
                f"not have attribute '{key}'"
            )
        super().__setattr__(key, value)




class PackagesNotFound(AnnotatedDataType, Exception):
    packages: List[str]
    wanted_by: Optional[List[str]] = None

    def __init__(self, packages: List[str], wanted_by: Optional[List[str]] = None) -> None:
        AnnotatedDataType.__init__(self, packages=packages, wanted_by=wanted_by)
        message = ', '.join(packages)
        if wanted_by:
            message += f" wanted by {', '.join(wanted_by)}"
        Exception.__init__(self, message)


class PackagesNotFoundInRepo(PackagesNotFound):
    pass


def main():
    try:
        raise PackagesNotFoundInRepo(packages=['a', 'b', 'c'])
    except PackagesNotFound as exc:
        print(exc.packages)
        #      ^ here pylint is NOT complaining
    try:
        raise PackagesNotFoundInRepo(packages=['a', 'b', 'c'])
    except PackagesNotFoundInRepo as exc:
        print(exc.packages)
        #     ^ [pylint] no-member: Instance of 'PackagesNotFoundInRepo' has no 'packages' member


if __name__ == "__main__":
    main()

[oshotton]

I think there is the same issue with .__annotations__. The example below is with a TypedDict but I imagine it is the same for all uses of .__annotations__.

from typing import TypedDict


class Example(TypedDict):
    string: str
    integer: int
    boolean: bool


print(Example.__annotations__)

Outputs:
{'string': <class 'str'>, 'integer': <class 'int'>, 'boolean': <class 'bool'>}

But pylint complains:
scratch.py:10:6: E1101: Class 'Example' has no '__annotations__' member (no-member)

[actionless]

i slightly updated my previous message, because the main point was not the annotations (which also indeed are not working there)

[fenuks]

As for __annotations__, no-member warning is indeed also issued for other kind of typed things in typing module, e.g. NamedTuple:

from typing import NamedTuple


class Foo(NamedTuple):
    foobar: str

print(Foo.__annotations__)

test.py:7:6: E1101: Class 'Foo' has no '__annotations__' member (no-member)

$ pylint --version
pylint 2.10.2
astroid 2.7.2
Python 3.9.6 (default, Aug 23 2021, 11:20:01) 

[cdce8p]

This issues seems to be fixed when testing with the latest pylint version.
If you still encounter issues, please report back and I'll reopen it.

[fenuks]

Latest tagged version? With

$ pylint --version
pylint 2.11.1
astroid 2.8.2
Python 3.9.7 (default, Oct 10 2021, 15:13:22) 
[GCC 11.1.0]

for the example I posted above problem still persists.

[cdce8p]

@fenuks I'd tested it with Python 3.10 which works.
However, you're right at least __annotations__ is still broken for Python < 3.10

I can't reproduce the original issue with Context.write though. Even not with Python 3.8

[tucked]

Just like #3233, the original issue (not sure exactly where __annotations__ ties in) appears to have been fixed in 2.5.0, likely because astroid was upgraded:

python3.6 -m venv venv
venv/bin/python -m pip install pylint==2.4.4
venv/bin/pylint sscce.py  # repro
venv/bin/python -m pip install astroid~=2.4.0
venv/bin/pylint sscce.py  # NO repro

[Pierre-Sassoulas]

Closing as the main issue was fixed, and I opened #7126 for the one that appeared along the way.