xen, guest_tools: add type hints

[glehmann]

This allows more validation both in the CI and when writing the tests in our IDEs.

This work was mostly done with AI, validated by the code checkers, and manually cleaned up by me.

[TSnake41]

What is this import ?

[olivierh-pro]

According to documentation (PEP 563), this import allows to declare type annotation that can be evaluated even if it is not in the scope yet.

[fallen]

What is this import ?

This https://docs.python.org/3/library/__future__.html#future__.annotations ?

[fallen]

After reading a bit it seems this line will turn into a SyntaxError in 1 or 2 Python releases, right?

[fallen]

According to documentation (PEP 563), this import allows to declare type annotation that can be evaluated even if it is not in the scope yet.

But it seems PEP 563 is now replaced by PEP 649 itself supplemented by PEP 749.
And PEP 749 says:

from __future__ import annotations (PEP 563) will continue to exist with its current behavior at least until Python 3.13 reaches its end-of-life. Subsequently, it will be deprecated and eventually removed.

See https://peps.python.org/pep-0749/

[glehmann]

We use from __future__ import annotations as a way to ease imports when using the type annotations.
It's already often used in this project:

$ rg 'from __future__ import annotations' | wc -l
28

It will eventually be deprecated, but it isn't yet in the last python (3.14.3). It is the way to go for the targeted python version (3.11) by this project.

[olivierh-pro]

According to documentation (PEP 563), this import allows to declare type annotation that can be evaluated even if it is not in the scope yet.