Add type annotations to cairo_renderer.py

[fmuenkel]

Overview: What does this pull request change?

More work towards completing #3375.

Motivation and Explanation: Why and how do your changes improve the library?

This PR includes some type annotations to utils/hashing.py to complete typing for cairo_renderer.py. Typing for utils/hashing.py should be completed in another PR.

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested

[fmuenkel]

As far as I can tell setting self.duration = 0.0, will not cause any problems, but it avoids having to deal with it being None when calculating number of static frames or self.time.

[fmuenkel]

For consistency with other methods and variables self.static_image should ideally be renamed to self.static_frame, but that can be done in another PR.

[chopan050]

Thanks for the type annotations, especially those for manim.utils.hashing! That's a pretty difficult module to type properly.

I left some change requests:

[chopan050]

Despite the name, iterable can be either a Sequence or a dict, according to the code. Currently, iterable can't be really an Iterable, because _iter_check_list calculates its length, something which not all iterables have (like map, range or filter).

EDIT: it is actually pretty easy to rewrite _iter_check_list to accept any iterables. See my suggestion below.

The name of this parameter (and function) should probably be changed.

Now, we could simply type iterable as Sequence[Any] | dict[Any, Any], but may I suggest the following overloads to indicate that, if iterable is a Sequence, the function returns a list and, if it's a dict, it returns a dict:

Suggested change

	def _cleaned_iterable(self, iterable: Iterable[Any]) -> list[Any] | dict[Any, Any]:
	@overload
	def _cleaned_iterable(self, iterable: Sequence[Any]) -> list[Any]: ...
	@overload
	def _cleaned_iterable(self, iterable: dict[Any, Any]) -> dict[Any, Any]: ...
	def _cleaned_iterable(self, iterable):

[chopan050]

MyPy requires this line, because, in the hypothetical case that _cleaned_iterable() receives a different object that's neither an iterable or a dictionary, the function would implicitly return None.

Now, as you mention, this shouldn't be reached, because the object should always be an iterable or a dictionary. In this case, I suggest raising an exception instead of silently returning the same iterable. In this way, if _cleaned_iterable() is being passed something different, we can catch the bug instead of silently omitting it:

Suggested change

	# mypy requires this line, even though it should not be reached.
	return iterable
	raise TypeError("'iterable' is neither an iterable nor a dictionary.")

[chopan050]

Suggested change

	def _key_to_hash(key) -> int:
	def _key_to_hash(key: Any) -> int:

[chopan050]

Suggested change

	def _iter_check_list(lst: list[Any]) -> list[Any]:
	def _iter_check_list(lst: Sequence[Any]) -> list[Any]:

It's also technically pretty easy to rewrite this function to allow any iterables, but I'm not so sure about allowing potentially infinite iterables:

        def _iter_check_list(lst: Iterable[Any]) -> list[Any]:
            processed_list = []
            for el in lst:
                el = _Memoizer.check_already_processed(el)
                if isinstance(el, Iterable):
                    new_value = _iter_check_list(el)
                elif isinstance(el, dict):
                    new_value = _iter_check_dict(el)
                else:
                    new_value = el
                processed_list.append(new_value)
            return processed_list

[chopan050]

Suggested change

	def _iter_check_dict(dct: dict) -> dict:
	def _iter_check_dict(dct: dict[Any, Any]) -> dict[Any, Any]:

[chopan050]

Can you please replace

        if isinstance(iterable, (list, tuple)):

with

        if isinstance(iterable, Sequence):

?

Lists and tuples pass that check.

[chopan050]

An issue with this is that animations_list is expected to be an iterable inside the function. If it's None, it will crash.

I noticed that CairoRenderer.play(self, scene, *args, **kwargs) passes scene.animations which is typed as list[Animation] | None. However, since scene.compile_animation_data(*args, **kwargs) is called before that, scene.animations will always be a list[Animation] at that point.

Therefore, instead of typing animations_list as Iterable[Animation] | None, you have to make an assertion inside CairoRenderer.play() that scene.animations is not None before the call to get_hash_from_play_call().