[Bug]: Type of Axes is unknown pyright #28022

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1. timhoffm commented on Apr 4, 2024

   

   timhoffm

   on Apr 4, 2024

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   The technical location of the class is matplotlib.axes._axes.Axes but it's re-imported in matplotlib.axes, which is our canonical public point of contact. Maybe pyright is stumbling over that?
2. haarisr commented on Apr 4, 2024

   

   haarisr

   on Apr 4, 2024

   Last edited by haarisr

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   Pyright understands matplotlib and goes under __init__.py but cannot find any source of axes there.

   Why not use Axes as the return type instead? It is imported in pyplot.py too. The same is used for functions returning Figure. I can make a PR if this is the intended direction.
3. timhoffm commented on Apr 4, 2024

   

   timhoffm

   on Apr 4, 2024

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   Yes, changing matplotlib.axes.Axes to Axes in type annotations in pyplot seems the right thing to do. ping @ksunden do you agree? A PR is welcome!
4. ksunden commented on Apr 4, 2024

   

   ksunden

   on Apr 4, 2024

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   See full explanations here:

   • Initial implementation of type stubs (mypy/PEP484) #24976 (comment)
   • https://github.com/matplotlib/matplotlib/pull/24976/files#r1152766000

   Short version is that sphinx had trouble resolving some things, so I resorted to the fully specified names in some cases. I think this particular example should be fine to be shortened, but the other places in pyplot.py where Axes was referred to as a union type broke sphinx in ways that I could not at the time figure out how to resolve.

   It is possible sphinx has changed how it resolves links in type hints since then, I have not checked.

   That said, this reference should work for type checkers, I'm pretty sure (and does work for mypy for instance, which is what we use for our CI).

   It is true that matplotlib.axes is not imported by default:

   >>> import matplotlib
   >>> matplotlib.axes
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/home/kyle/src/scipy/matplotlib/lib/matplotlib/_api/__init__.py", line 217, in __getattr__
       raise AttributeError(
   AttributeError: module 'matplotlib' has no attribute 'axes'

   Adding the explicit imports (I just did it in the if TYPE_CHECKING: block since its working around type checker limitations) appears to fix the problems (for some reason did not fix one of the backend_bases flags, not sure why):

   diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
   index 2376c62439..426892afca 100644
   --- a/lib/matplotlib/pyplot.py
   +++ b/lib/matplotlib/pyplot.py
   @@ -90,6 +90,9 @@ if TYPE_CHECKING:
        import PIL.Image
        from numpy.typing import ArrayLike
    
   +    import matplotlib.axes
   +    import matplotlib.artist
   +    import matplotlib.backend_bases
        from matplotlib.axis import Tick
        from matplotlib.axes._base import _AxesBase
        from matplotlib.backend_bases import RendererBase, Event

   The remaining flags I see from pyright in pyplot.py are largely due to either:

   a) types are narrowed in ways pyright doesn't (or can't) know e.g.:

   • we looked up an rcParam, so we know the type narrowed
   • we do a hasattr check before accessing an optional attribute

   b) a small handful of artist functions that do not get type hints because of the complexity of doing so (its not impossible, just never got around to it and didn't hold the rest of the work on it)

   • https://github.com/ksunden/matplotlib/blob/bd4469d1e4eebaa3d21f5e80aac4d76267a6a2d4/tools/boilerplate.py#L419

   I have no issue with paring down the number of flags we get with pyright, though mypy remains my preference for CI purposes for now (not totally opposed to both, but did not optimize for pyright). There were ~3000 flags from pyright that mypy did not flag when we first added type hints (10k if you include tests), so not trivial.

   I do use a pyright-based LSP/editor integration, but it doesn't play well with editable meson installs, so mostly don't get mpl flags unless I go looking for them.
5. haarisr commented on Apr 5, 2024

   

   haarisr

   on Apr 5, 2024

   Last edited by haarisr

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   I like the if TYPE_CHECKING solution better. It works for now and would not bother sphinx as well.

   Let me know if you want a PR for that.

   Off topic: I prefer pyright for now as it does not hang up once an error is encountered unlike pyright. Also it seems to have support for PEP 695 generics, and it has some strong arguments in its comparison to mypy. I would prefer mypy but it automatically skips if a type cannot be inferred and that to me is a big bummer. Pyright on the other hand does not need to append None on functions that do not return anything which is a bit less clutter imo.
6. oscargus

   added

   topic: typing

   on Apr 15, 2024
7. timhoffm

   closed this as completedin #28230on May 17, 2024
8. QuLogic

   added this to the v3.9.1 milestone on May 17, 2024