__path__ mangling in a non namespace package

[chaen]

Hi,

I have a use case which I am unsure whether it is covered by pylint or not.
I've been through quite a number of issues regarding namespace packages using pkgutil.extend_path, and I could verify that this works fine. Now, what I would like to do is to expose modules in a subdirectory as being part of an upper module. This works fine with python, but pylint gives me the no-name-in-module error.

Here is how to reproduce:

[chaen@notANamespace]$ ls -R
.:
__init__.py  module  useModule.py

./module:
impl  __init__.py

./module/impl:
__init__.py  myClass.py

The useModule.py just imports a class from module and instantiate it. The actual class is in the subdirectory impl, but I do not want this to be visible to the useModule script.

[chaen@notANamespace]$ cat useModule.py 
from module.myClass import MyClass
MyClass()
[chaen@notANamespace]$ cat module/__init__.py 
from pkgutil import extend_path
__path__ = extend_path(__path__, __name__ + '.impl')
[chaen@notANamespace]$ cat module/impl/myClass.py 
class MyClass(object):
  def __init__(self):
    print "Hello PyLint"

The __init__.py in the root and module/impl directories are empty

If I execute it in python, I get what I expect:

[chaen@notANamespace]$ python useModule.py 
Hello PyLint

Pylint however will complain

[chaen@notANamespace]$ pylint useModule.py 
No config file found, using default configuration
************* Module notANamespace.useModule
C:  1, 0: Module name "useModule" doesn't conform to snake_case naming style (invalid-name)
C:  1, 0: Missing module docstring (missing-docstring)
E:  1, 0: No name 'myClass' in module 'notANamespace.module' (no-name-in-module)
E:  1, 0: Unable to import 'module.myClass' (import-error)

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Your code has been rated at -50.00/10 (previous run: -50.00/10, +0.00)

So I am not sure what makes the namespace packages work and not that. Maybe this isn't the way to 'hide' a subdirectory in python anyway ?

In any case, this are the versions I am using:

[chaen@notANamespace]$ python --version
Python 2.7.15
[chaen@notANamespace]$ pylint --version
No config file found, using default configuration
pylint 1.9.3, 
astroid 1.6.5
Python 2.7.15 (default, May 16 2018, 17:50:09) 
[GCC 8.1.1 20180502 (Red Hat 8.1.1-1)]

Thanks for your help

[PCManticore]

Hi @chaen Thanks for reporting an issue. I think pylint is confused by the use of

from pkgutil import extend_path
__path__ = extend_path(__path__, __name__ + '.impl')

While we do have some support for namespace packages, unfortunately we cannot correctly infer what the second argument to extend_path is going to be, which is why you might see this error. I think this could be clearer with using explicit import in __init__ rather than this __path__ mangling.

[chaen]

Yes, it certainly would be clearer, but also less maintainable if I have to update the list of import in the __init__.py file everytime I add something in my submodule. Unless you have another idea in mind ? :)