bpo-39659: Route calls from pathlib.Path to os.getcwd() via the path accessor

[barneygale]

(from the bug description:) Whereas most calls to os functions from pathlib.Path methods happen via pathlib._Accessor methods, retrieving the current working directory does not. This problem occurs when calling the pathlib.Path.cwd(), ~resolve() and ~absolute() methods.

https://bugs.python.org/issue39659

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[barneygale]

This change should have no functional effect beyond the addition of pathlib._NormalAccessor.getcwd(). which is an internal API anyway. The idea is to make the "accessor" abstraction less leaky and perhaps work our way towards a more extensible pathlib (see here)

[pitrou]

This is a quirky way to implement it. If the accessor becomes tied to the class rather than specific instances, perhaps it should become a class-level attribute?

[barneygale]

It's very similar to how home() is implemented immediately below.

Agree generally that the accessor should be a class attribute and not an instance attribute.

[barneygale]

I've replaced cls() with cls in this method, and home() for consistency.

[barneygale]

Well, that didn't work at all! Looks like:

• _accessor is set in _init(), at least until bpo-40038: pathlib: remove partial support for preserving accessor when modifying a path #19342 lands
• _flavour is set in __new__().

Reverting to previous patch (the one you reviewed).

[zooba]

@barneygale This one looks like the conflict is meaningful? (And it's new because I merged one of your other changes, I think)

[barneygale]

Thank you! Rebased :-)