Shadow Import Issue

This repo includes a reproduction of an import issue when using setuptools>=64.0.0 and Cython when installed in editable mode.

This issue occurs when importing a module from a parent module which has the same name as a sibling module.

For example:

├── shadow_import_issue
│   ├── __init__.py
│   ├── c_exts
│   │   ├── __init__.py
│   │   ├── _child.pyx
│   │   └── shadow.py
│   ├── shadow.py
│   └── sub
│       ├── __init__.py
│       ├── child.py
└──     └── shadow.py

When trying to import shadow_import_issue.shadow from shadow_import_issue.c_exts._child it will import shadow_import_issue.c_exts.shadow instead.

This issue is not present when importing shadow_import_issue.shadow from shadow_import_issue.sub.child (pure-python version).

Running

git clone https://github.com/brettlangdon/shadow-import-issue.git
cd ./shadow-import-issue/
docker build -t shadow-import-issue .
docker run --rm shadow-import-issue

Expected output is to fail with:

<module 'shadow_import_issue.shadow' from '/src/shadow_import_issue/shadow.py'>
VAR
<module 'shadow_import_issue.c_exts.shadow_import_issue.shadow' from '/src/shadow_import_issue/c_exts/shadow.py'>
Traceback (most recent call last):
  File "/src/test.py", line 1, in <module>
    import shadow_import_issue
  File "/src/shadow_import_issue/__init__.py", line 3, in <module>
    import shadow_import_issue.c_exts._child  # isort:skip
  File "shadow_import_issue/c_exts/_child.pyx", line 4, in init shadow_import_issue.c_exts._child
    print(shadow_import_issue.shadow.VAR)
AttributeError: module 'shadow_import_issue.c_exts.shadow_import_issue.shadow' has no attribute 'VAR'

The module and variable will import fine with Python, but will fail the import from the Cython module.

Analysis

• This only happens with editable install
• This only occurs with setuptools>=64.0.0
  • setuptools>=64.0.0 changed from using .egg-link to .pth + editable loader
• The module loaded by Cython has the name shadow_import_issue.c_exts.shadow_import_issue.shadow and is loaded from shadow_import_issue/c_exts/shadow.py
• The issue does not happen with Cython==3.0.0a11
  • diff of ImportExport.c
• Changing to a relative import resolves the issue
  • from .. import shadow will load the correct module