Remove type comment in favor of PEP 526 for variable annotation

[merelcht]

Description

Addresses #2078

Development notes

The problem found in #2078 was caused by the following: PyCQA/pyflakes#747 (comment) Essentially, flake8 doesn't support type checking in comments anymore with the # type: ... syntax. Instead it now looks for the PEP 526 syntax for variable annotation: https://peps.python.org/pep-0526/

Checklist

• Read the contributing guidelines
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added a description of this change in the RELEASE.md file
• Added tests to cover my changes

[astrojuanlu]

Thanks @merelcht! I was always a fan of type: comments, I guess Python is solidly heading towards types as annotations...

Some questions:

• What's the role of flake8 in typing? Does it replace MyPy, or it only checks that the annotations are correct?
• May I suggest using import typing as t? (Silly personal preference, but I think it's nice to avoid polluting the global namespace with typing stuff, and instead I prefer to do t.Any, t.TypedDict and such)
• May I suggest adding from __future__ import annotations to leverage PEP 585 and hence be able to do list[str] instead of t.List[str]? (Available from Python 3.7)
• Where it makes sense for this PR (without having to overhaul the whole codebase) may I suggest adding from __future__ import annotations to leverage PEP 604 and hence use str | None instead of t.Optional[str] and str | bytes instead of t.Union[str, bytes]?

[merelcht]

Some questions:

• What's the role of flake8 in typing? Does it replace MyPy, or it only checks that the annotations are correct?

I think we've always had flake8 on Kedro, and never fully leveraged MyPy to its full abilities, see #2156. For this specific issue flake8 was checking if all imports are being used in the code and before this change it was failing any imports that were only used in type: comments.

• May I suggest using import typing as t? (Silly personal preference, but I think it's nice to avoid polluting the global namespace with typing stuff, and instead I prefer to do t.Any, t.TypedDict and such)

Is this common practice? I'm not sure I like it 😄 haha! Perhaps we can make a follow up task with several PEP update suggestions and just vote as a team?

• May I suggest adding from __future__ import annotations to leverage PEP 585 and hence be able to do list[str] instead of t.List[str]? (Available from Python 3.7)

This one I do like!

• Where it makes sense for this PR (without having to overhaul the whole codebase) may I suggest adding from __future__ import annotations to leverage PEP 604 and hence use str | None instead of t.Optional[str] and str | bytes instead of t.Union[str, bytes]?

Is this one also available from Python 3.7?

[astrojuanlu]

I see, thanks! Okay with keeping from typing import *, I had to try 😸

About PEP 604, I'm not sure, it's not clearly written in the PEP 🤔

[merelcht]

I'll create a new PR to leverage PEP 585.

[astrojuanlu]

LGTM!

[noklam]

Looks good to me!