False positive import-error

[sam-s]

Steps to reproduce

in an empty directory:

1. file a.py:

def a():
    print("a")

2. file b.py

import a
print(a.a())

3. empty file __init__.py

Current behavior

pylint b.py
b.py:1: [E0401(import-error), ] Unable to import 'a'

Expected behavior

no diagnostics

Important note

if you remove __init__.py, the import-error disappears.

pylint --version output

pylint 2.6.0
astroid 2.4.2
Python 3.9.1 (default, Dec 10 2020, 10:36:35)
[Clang 12.0.0 (clang-1200.0.32.27)]

[bvobart]

Love how minimal this example is, I've been able to reproduce this behaviour exactly, including that the false positive import-error disappears after removing __init__.py

I'm doing research on static code analysis in machine learning code, where I run Pylint on a number of Python ML projects (after installing their requirements in a virtualenv). While this currently only includes 8 projects so far, Pylint reports each one of those as having several import-errors. I've noticed that most of those are imports from local files not being resolved correctly, even though they do indeed exist on the filesystem.

$ pylint --version
pylint 2.6.0
astroid 2.4.2
Python 3.8.6 (default, Sep 30 2020, 04:00:38) 
[GCC 10.2.0]

[hippo91]

@sam-s thanks for your report. I can reproduce it.

[jacobtylerwalls]

I'm seeing this fixed in astroid 2.12. Let's add this test case to pylint.

[DanielNoord]

@jacobtylerwalls Is this still the case? 🚀

[jacobtylerwalls]

No, I was probably testing in a directory on sys.path, and we now know that's been polluting our test results.

Failing test for unittest_lint.py:

def test_import_sibling_module_from_explicit_package(initialized_linter: PyLinter) -> None:
    linter = initialized_linter
    with tempdir() as tmpdir:
        create_files(["siblingone.py", "siblingtwo.py", "__init__.py"], tmpdir)
        with open("siblingone.py", "w", encoding="utf-8") as f:
            f.write(
                """\"\"\"This module contains siblingone().\"\"\"
def siblingone():
    print("siblingone")
"""
            )
        with open("siblingtwo.py", "w", encoding="utf-8") as f:
            f.write(
                """\"\"\"This module imports siblingone().\"\"\"
import siblingone
print(siblingone.siblingone())
"""
            )
        linter.check(["siblingtwo"])
        assert not linter.stats.by_msg