Consider quotes inside format-specs when choosing the quotes for an f-string

[MichaReiser]

Summary

Fixes #13935

Test Plan

Added test

[github-actions]

ruff-ecosystem results

Formatter (stable)

✅ ecosystem check detected no format changes.

Formatter (preview)

✅ ecosystem check detected no format changes.

[MichaReiser]

Hmm, this now leads to invalid syntax for "aaa " f'{1=: "abcd {'aa'}}'

[MichaReiser]

Okay, this is a pre-existing issue, but not one that gets fixed by this PR.

f'{1=: "abcd {'aa'} \'\'}'

We can't change the outer quotes because the format-spec quotes then become the "closing" quotes of the entire-fstring (which they shouldn't). That means we have to preserve the quotes if:

• an expression has a format spec that contains the current quote character
• the expression uses debug text

[MichaReiser]

I'll do another review myself of the code changes with a fresh mind tomorrow morning but I think this is mostly correct.

[dhruvmanila]

The only change here is the addition of this condition to return the quote that needs to be preserved? I'm curious to know why was this condition not present before this? It seems like it should've been present.

[MichaReiser]

Not 100%. I would have to remind myself of how the pre 312 fstring formatting works again. It might also just be that we were missing a test.