Bug report

Bug description:

Calling repr() on a ModuleType instance can fail with AttributeError on py312+, due to changes made in #98870. This is because the implementation of importlib._bootstrap._module_repr_from_spec assumes that all loaders will have a _path attribute. But if the module had a custom loader, that won't necessarily hold true: _path is an undocumented, internal, private attribute that CPython's import loaders have, but custom third-party loaders won't necessarily have.

An easy way to see this is the following (in a py312 venv with setuptools installed):

Python 3.12.0 (tags/v3.12.0:0fb18b0, Oct  2 2023, 13:03:39) [MSC v.1935 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from setuptools._vendor import packaging
>>> repr(packaging)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<frozen importlib._bootstrap>", line 545, in _module_repr
  File "<frozen importlib._bootstrap>", line 830, in _module_repr_from_spec
AttributeError: 'VendorImporter' object has no attribute '_path'

setuptools implements the custom VendorImporter loader here: https://github.com/pypa/setuptools/blob/b1bf87be7869df40872e947e27296ef87e3125ae/setuptools/extern/__init__.py#L5-L70. Instances of VendorImporter do not have a _path attribute.

This kind of thing trips up external tools such as mypy's stubtest.py script, which calls repr() on arbitrary instances of types.ModuleType on certain code paths and (reasonably) expects that to always succeed: https://github.com/python/mypy/blob/1200d1d956e589a0a33c86ef8a7cb3f5a9b64f1f/mypy/stubtest.py#L224

Cc. @FFY00 and @jaraco, as participants in #98139 (the issue #98870 was linked to)

CPython versions tested on:

3.12

Operating systems tested on:

Windows

Linked PRs

• gh-112414: Fix AttributeError when calling repr() on a namespace package imported with a custom loader #112425
• gh-112414: Fix repr for custom loader #112436
• [3.12] gh-112414: Fix AttributeError when calling repr() on a namespace package imported with a custom loader (GH-112425) #112440
• gh-112414: Add additional unit tests for calling repr() on a namespace package #112475
• [3.12] gh-112414: Add additional unit tests for calling repr() on a namespace package (GH-112475) #112480