Case insensitive when importing modules on Mac

[DionysusG]

It seems that mypy fails to deal with the case sensitive imports; it behaves abnormally when importing a object from a module if the object's name is case-incentively the same as the module's name.

Clarify this issue with a example. Suppose we have such a directory structure

├── b
│   ├── \__init__.py
│   └── a.py
└── test.py

in b/a, we define class A and in b/init.py we put from a import A; in test.py we put from b import A. In this situation, python test.py normally emits no error while mypy test.py gives

b/__init__.py:1: error: Name 'A' already defined

This behavior seems to be due to the case insensitivity of mac's file system.

[gvanrossum]

This doesn't look like it's related to the case insensitive filesystem -- mypy is careful not to be confused by that. I have tried to reconstruct the situation you described but I don't get an error from mypy. I had to change b/__init__.py to

from .a import A

to deal with the relative imports.

If you still want to pursue this, please show the exact contents of your files. If not, please close the issue.

(Also, I fixed up your post slightly -- hope I didn't destroy any information.)

[DionysusG]

Sorry for my inaccuracy and carelessness about describing the file contents. In b/init.py, it is indeed

from .a import A

Also, there is a crucial thing I forgot to mention. In b/a, there is

class A():
    pass

so that import A from a in b/init.py would make sense.

Hope you can reconstruct the situation now.

[gvanrossum]

No, I still don't see it. Can you zip up the files you are using (the tree b/ and the file test.py) and attach them here? (Or upload somewhere and link from here, or create a gist with all of them? Also, what is the exact mypy invocation you are using, what mypy version are you using, and what platform? (Is it OS X? What version?)

I have tested a variety of case-sensitivity issues and each time mypy does the right thing.

[DionysusG]

I was using mypy 0.4.1, and mypy 0.4.3 worked perfectly on the constructed situation. By virtualenving different versions, I think this issue was solved in mypy 0.4.2.

Thank you for the patience.