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## Summary
<!-- What's the purpose of the change? What does it do, and why? -->
This PR fixes#7172 by suppressing the fixes for
[docstring-missing-returns
(DOC201)](https://docs.astral.sh/ruff/rules/docstring-missing-returns/#docstring-missing-returns-doc201)
/ [docstring-extraneous-returns
(DOC202)](https://docs.astral.sh/ruff/rules/docstring-extraneous-returns/#docstring-extraneous-returns-doc202)
if there is a surrounding line continuation character `\` that would
make the fix cause a syntax error.
To do this, the lints are changed from `AlwaysFixableViolation` to
`Violation` with `FixAvailability::Sometimes`.
In the case of `DOC201`, the fix is not given if the non-break line ends
in a line continuation character `\`. Note that lines are iterated in
reverse from the docstring to the function definition.
In the case of `DOC202`, the fix is not given if the docstring ends with
a line continuation character `\`.
## Test Plan
<!-- How was it tested? -->
Added a test case.
Fix#9080
Example, where `[]` is a 2 byte non-breaking space:
```
def f():
""" Docstring header
^^^^ Real indentation is 4 chars
docstring body, over-indented
^^^^^^ Over-indentation is 6 - 4 = 2 chars due to this line
[] [] docstring body 2, further indented
^^^^^ We take these 4 chars/5 bytes to match the docstring ...
^^^ ... and these 2 chars/3 bytes to remove the `over_indented_size` ...
^^ ... but preserve this real indent
```
Closes https://github.com/astral-sh/ruff/issues/8695
We track the smallest offset seen for overindented lines then only
reduce the indentation of the lines that far to preserve indentation in
other lines. This rule's behavior now matches our formatter, which is
nice.
We may want to gate this with preview.
GiGaGon
konsti
Zanie Blue
Charlie Marsh