Added Python2 compatible type hints

[Avasam]

Closes #151

Just like #161, but addresses @JohannesBuchner concerns #151 (comment)

I am wondering how to do this with the least amount of future maintenance effort. I am worried that the stub file may become outdated if not care is taken.

The refactor from a single file module to a package was necessary for the inclusion of py.typed, which lets type checkers know to not look for type stubs as types are inlined.
See: https://peps.python.org/pep-0561/#packaging-type-information

[Avasam]

One issue with this is that Pyright won't recognize that I can substract two ImageHash, might be a bug on their end, I'll raise an issue.

Edit: This was an issue on my side and unrelated to these changes.

[JohannesBuchner]

Thank you for looking into this, @Avasam

[JohannesBuchner]

Do we have to add something in the testing / CI to check whether the typing stuff works? For example, a test that the types are not faulty, and a test that a calling code with the wrong type can be identified by a typing checker.

[JohannesBuchner]

the python3.9 CI run is complaining that numpy is too new: error: numpy 1.23.1 is installed but numpy<1.23.0,>=1.16.5 is required by {'scipy'}. Odd that conda installs this combination.

[Avasam]

Do we have to add something in the testing / CI to check whether the typing stuff works? For example, a test that the types are not faulty, and a test that a calling code with the wrong type can be identified by a typing checker.

You could run type checkers to ensure that the returned and used types match the annotations. Popular ones are mypy and pyright. Typeshed also tests against pytyped.

I am quite familiar with pyright so I could add it and configure it. A bit less so with the other two, but I don't think it's anything too complicated. Would you like me to add them as part of this PR or separately?

the python3.9 CI run is complaining that numpy is too new: error: numpy 1.23.1 is installed but numpy<1.23.0,>=1.16.5 is required by {'scipy'}. Odd that conda installs this combination.

I've noticed that with my other PR as well. Conda doesn't support Environment markers (which would be an easy fix), but it has something called Preprocessing selectors instead that we can try to use.

[Avasam]

the python3.9 CI run is complaining that numpy is too new: error: numpy 1.23.1 is installed but numpy<1.23.0,>=1.16.5 is required by {'scipy'}. Odd that conda installs this combination.

Unrelated to conda. The step that tested the setup.py install (which conda doesn't care about the existence of setup.py) was using a deprecated and obsolete way of installing.

$ python setup.py install
running install
/usr/share/miniconda/envs/test/lib/python3.9/site-packages/setuptools/command/install.py:34: SetuptoolsDeprecationWarning: setup.py install is deprecated. Use build and pip and other standards-based tools.
/usr/share/miniconda/envs/test/lib/python3.9/site-packages/setuptools/command/easy_install.py:144: EasyInstallDeprecationWarning: easy_install command is deprecated. Use build and pip and other standards-based tools.

[coveralls]

Coverage decreased (-4.5%) to 85.0% when pulling af1b868 on Avasam:python2-typing into 0abd487 on JohannesBuchner:master.

[JohannesBuchner]

I am okay with merging this if it is ready from your side.

[JohannesBuchner]

Thank you for your work on this! I suppose I should make a release now.

[Avasam]

Thank you for your work on this! I suppose I should make a release now.

You're welcome! I learned a lot about typing since I opened the issue last year. So I decided to give it a go. And it's better to have it directly as part of the library rather than in typeshed.
I'm installing from github for now. git+https://github.com/JohannesBuchner/imagehash#egg=ImageHash

[JohannesBuchner]

release 4.3 is out, please test it and let me know whether it works for you.

I made some substantial changes in the code regarding python version checking, hope it did not break things. If it did, we need better CI checks.