💚 Add mypy in CI

[tkoyama010]

Let's add mypy in CI. We need type hint for this.

[Codecov]

Codecov Report

Merging #47 into master will decrease coverage by 0.10%.
The diff coverage is 98.82%.

@@            Coverage Diff             @@
##           master      #47      +/-   ##
==========================================
- Coverage   98.06%   97.95%   -0.11%     
==========================================
  Files           6        6              
  Lines         516      539      +23     
==========================================
+ Hits          506      528      +22     
- Misses         10       11       +1     

[GuillaumeFavelier]

As described in mypy documentation, by default mypy will assume the functions to be dynamically typed and only check the imported modules. I went ahead and ignored those imports in favor of --disallow-untyped-defs. I think it suits better your intention @tkoyama010 ?

[tkoyama010]

Thanks for @GuillaumeFavelier 's work.

[tkoyama010]

☝️ This error is the Type Annotation problem of Python3.5. I think we should finish support of Python3.5.
See #60 and pyvista/pyvista#905 .

[tkoyama010]

This is ready for reviews @akaszynski @GuillaumeFavelier @banesullivan @larsoner

[akaszynski]

I'm all for static type checking, especially since it's optional. While this won't replace unit testing, it can help us identify errors (and help the IDE). I'd like to hear the opinions of the other contributors as well.

[banesullivan]

I haven't always been a fan of type annotations but lately, they have been growing on me. Thanks for taking this on to move pyvistaqt in a good direction, @tkoyama010!

This works well here because it is a smaller codebase, but I think it would be tough to do in pyvista core

[akaszynski]

This works well here because it is a smaller codebase, but I think it would be tough to do in pyvista core

Agreed. We can just do it in chunks since mypy is optional.