id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
28241	module_has_submodule()  doesn't work correctly if the module_name argument is a dotted path	tkhyn	tkhyn	"Hello,

Porting a django project from python 2.7 to 3.6, I noticed an issue with `utils.module_loading.module_has_submodule`. At some stage my project makes use of `autodiscover_modules('module.submodule')` to try and discover modules that are nested in my app.

I'm using django 1.11.1, but this bug probably also affects 1.8 as the code of `module_has_submodule` is the same.

So here we go, with python 2.7 we have the expected behavior (taking contenttypes as an example app):

{{{
python2.7
>>> from django.utils.module_loading import module_has_submodule
>>> from django.contrib import contenttypes
>>> module_has_submodule(contenttypes, 'invalid_module.submodule')
False
>>> module_has_submodule(contenttypes, 'checks')
True
>>> module_has_submodule(contenttypes, 'checks.submodule')
False
}}}

But, with python 3.6

{{{
python3.6
>>> from django.utils.module_loading import module_has_submodule
>>> from django.contrib import contenttypes
>>> module_has_submodule(contenttypes, 'invalid_module.submodule')
  File ""<console>"", line 1, in <module>
  File ""d:\dev\.env\buildout\eggs\django-1.11.1-py3.6.egg\django\utils\module_loading.py"", line 79, in module_has_submodule
    return importlib_find(full_module_name, package_path) is not None
  File ""D:\dev\.env\venv\buildout\lib\importlib\util.py"", line 88, in find_spec
    parent = __import__(parent_name, fromlist=['__path__'])
ModuleNotFoundError: No module named 'django.contrib.contenttypes.invalid_module'
>>> module_has_submodule(contenttypes, 'checks')
True
>>> module_has_submodule(contenttypes, 'checks.submodule')
  File ""<console>"", line 1, in <module>
  File ""d:\dev\.env\buildout\eggs\django-1.11.1-py3.6.egg\django\utils\module_loading.py"", line 79, in module_has_submodule
    return importlib_find(full_module_name, package_path) is not None
  File ""D:\dev\.env\venv\buildout\lib\importlib\util.py"", line 89, in find_spec
    return _find_spec(fullname, parent.__path__)
AttributeError: module 'django.contrib.contenttypes.checks' has no attribute '__path__'
}}}

From the replies I got on the python bug tracker (http://bugs.python.org/issue30436) the `AttributeError` will be converted to `ModuleNotFoundError` only in Python 3.7, but that behavior is apparently not expected to be fixed in previous versions.

We'll definitely need to catch `ModuleNotFoundError`, and to have a proper fix for python < 3.7 we'll need to:
- either catch `AttributeError` as well. The problem I see is ``AttributeError`` is too broad and may result in 'false catches'
- or convert a dotted path to [package, name] (basically do what ``find_spec`` actually does) but detect if the  module has a `__path__` attribute  before calling `find_spec` so that it can not raise exceptions

What are your thoughts ?"	Bug	closed	Utilities	1.11	Normal	fixed	module_loading python3		Accepted	1	0	0	0	0	0