Implement type checking with github actions

[roberto-arista]

Hey @benkiel and @knutnergaard,

I took a quick look into this and have a couple of questions:

• Should I continue working on the v1 branch?
• Should the checks be implemented using tox?
• @knutnergaard, did you use mypy or pyright when updating the code? I ran a quick scan of the v1 codebase with mypy error highlighting and noticed several issues.

Looking forward to your input! 👋

[knutnergaard]

@roberto-arista

I used mypy when updating the code and reported the issues which I was unable to solve in #739, but these are, at least for the most part, related to conflicts with the base.py module.

[roberto-arista]

If these can't be solved and we want to implement type checking in CI, we need to flag each of them with # type: ignore. Do you see other options?

[knutnergaard]

No, I agree, but I think these errors can be solved. I'm just not comfortable making adjustments to the base module logic without a second opinion from someone with more intimate knowledge of the codebase.

We could make a list of all unique errors in the annotated modules, and make a PR to solve them.

[benkiel]

@roberto-arista Yes, keep to the v1 branch, and yes have tox run the checking

[knutnergaard]

These mypy errors are currently unresolved:

1. [resolved in https://github.com/Resolve mypy errors. #807] Incompatibility in signature of _reprContents between BaseObject and it's subclasses, e.g.,

   glyph.py:85: error: Signature of "_reprContents" incompatible with supertype "BaseObject"  [override]
   glyph.py:85: note:      Superclass:
   glyph.py:85: note:          @classmethod
   glyph.py:85: note:          def _reprContents(cls) -> List[str]
   glyph.py:85: note:      Subclass:
   glyph.py:85: note:          def _reprContents(self) -> List[str]

2. [resolved in https://github.com/Resolve mypy errors. #807] Incompatibility in signature of isCompatible between InterpolationMixin and it's subclasses, e.g.,

   glyph.py:2790: error: Signature of "isCompatible" incompatible with supertype "InterpolationMixin"  [override]
   glyph.py:2790: note:      Superclass:
   glyph.py:2790: note:          def isCompatible(self, other: Any, cls: Type[Any]) -> Tuple[bool, Any]
   glyph.py:2790: note:      Subclass:
   glyph.py:2790: note:          def isCompatible(self, other: BaseGlyph) -> Tuple[bool, str]

3. [resolved in https://github.com/Resolve more mypy errors. #808] base.reference returning a wrapper rather than the actual object , e.g.,

   contour.py:125: error: Incompatible types in assignment (expression has type "Callable[[], Any]", variable has type "Optional[BaseGlyph]")  [assignment]

4. [resolved in https://github.com/Resolve mypy errors. #794] The annotated return type of isCompatible being str rather than BaseCopatibilityReporter in InterpolationMixin subclasses, e.g.,

   contour.py:534: error: "str" has no attribute "fatal"  [attr-defined]
   contour.py:534: error: "str" has no attribute "warning"  [attr-defined]
   contour.py:535: error: "str" has no attribute "fatal"  [attr-defined]
   contour.py:537: error: "str" has no attribute "warning"  [attr-defined]

   This annotation is based on original documentation, but probably should be the appropriate BaseCompatibilityReporter subclass.

5. [resolved in https://github.com/Add abstract members. #803] References to attributes not defined in class or base class, e.g.,

   contour.py:657: error: "BaseContour" has no attribute "_reverseContour"
   layer.py:52: error: "_BaseGlyphVendor" has no attribute "defaultLayer"  [attr-defined]
   

6. [resolved in https://github.com/Resolve more mypy errors. #808] Former weakrefs still being called in getters or setters of parent objects, e.g.,

   lib.py:112: error: "BaseFont" not callable  [operator]

7. [resolved in https://github.com/Add abstract members. #803] SelectionMixin. _getSelectedSubObjects passing _BaseGlyphVendor while expecting CollectionType[Any]:

   ayer.py:477: error: Argument 1 to "_getSelectedSubObjects" of "SelectionMixin" has incompatible type "_BaseGlyphVendor"; expected "Union[List[Any], Tuple[Any, ...]]"  [arg-type]
   layer.py:498: error: Argument 1 to "_setSelectedSubObjects" of "SelectionMixin" has incompatible type "_BaseGlyphVendor"; expected "Union[List[Any], Tuple[Any, ...]]"  [arg-type]
   

@roberto-arista @benkiel This is what I have so far. Any suggestions on how to fix these, preferably without the use of type: ignore?

[roberto-arista]

Hey @knutnergaard!

1. they return the same type, is it because of the superclass method being a classmethod?

To be honest, I don't know the code base well enough to provide a solution for any of these issues, sorry.

[knutnergaard]

@roberto-arista Yes, that's correct. Though I see no reason why it should be a classmethod in the BaseObject class.

[benkiel]

For 4: yes, should be BaseCompatibilityReporter

[knutnergaard]

Error 4 resolved in #794