Add support for type aliases introduced in Python 3.12 via PEP 695

[Stausssi]

Hi,

I've started updating my codebases to Python 3.12, including adding type aliases via type CustomType = dict[str, int] | list[int] and sharing them across files via from src.module import CustomType. The code itself works fine, but building the documentation does not:
Cannot resolve import of src.module.CustomType in src.other_module
Since I use warnings-as-errors by default, this currently breaks all my documentation builds. Setting suppress_warnings = ["autoapi"] does get rid of the warning.
There might be a correlated issue in sphinx-doc/sphinx#11561.

I'm also not quite sure how these type aliases are supposed to be documented and opened a discussion on python.org, but this does not resolve the import issues.

[etienneschalk]

Hello,

I do not have exactly the same issue, as luckily my code base only use types declared with the type keyword inside of the module where they were declared.

However, such declared types are rendered as plain text: no "unwrapping" of the nested types like done before, nor a link to a potential type definition

I am not sure if this is a problem on sphinx-autoapi itself, or upstream on autodoc and other tools.

A suggestion: add a "Types" section that summarizes the type definitions. In function signatures, add links to the type definition. We can even push further and imagine having a tooltip like in IDEs displaying information about the type

Example of code using type keyword:

type PuzzleInput = list[tuple[list[str], int]]
type HandAndBid = tuple[list[int], int]
type PuzzleMappedInput = list[HandAndBid]
type SortedByHandType = dict[Any, list[HandAndBid]]

@dataclass(kw_only=True)
class AdventOfCodeProblem202307(AdventOfCodeProblem[PuzzleInput]):
    year: int = 2023
    day: int = 7

    def solve_part_1(self, puzzle_input: PuzzleInput): ...

When hovering PuzzleInput the mouse over the solve_part_1 method in VSCode, the full unwrapped type is shown in a tooltip:

(type alias) PuzzleInput: type[list[tuple[list[str], int]]]

When hovering SortedByHandType, the unwrapped definition also shows up in a tooltip

(type alias) SortedByHandType: type[dict[Any, list[tuple[list[int], int]]]]

[AWhetter]

Just noting that this is currently blocked due to the lack of a way to document type aliases in Sphinx (sphinx-doc/sphinx#7896). astroid already has support for parsing type aliases.

[AWhetter]

It seems that implementing type aliases in Sphinx is going to take some time. In the meantime, I've pushed a commit that will workaround the limitation by rendering PEP-695 type usage as an assignment to a variable that's annotated with typing.TypeAlias.
Once we have proper PEP-695 support on Sphinx we can change AutoAPI to render these properly.

[AWhetter]

Sphinx 7.4.0 introduced this feature so we should now be able to proceed with proper type alias support.