A small PR that just updates the various settings/configurations to
allow Python 3.14. At the moment selecting that target version will
have no impact compared to Python 3.13 - except that a warning
is emitted if the user does so with `preview` disabled.
This PR promotes the fix applicability of [readlines-in-for
(FURB129)](https://docs.astral.sh/ruff/rules/readlines-in-for/#readlines-in-for-furb129)
to always safe.
In the original PR (https://github.com/astral-sh/ruff/pull/9880), the
author marked the rule as unsafe because Ruff's type inference couldn't
quite guarantee that we had an `IOBase` object in hand. Some false
positives were recorded in the test fixture. However, before the PR was
merged, Charlie added the necessary type inference and the false
positives went away.
According to the [Python
documentation](https://docs.python.org/3/library/io.html#io.IOBase), I
believe this fix is safe for any proper implementation of `IOBase`:
>[IOBase](https://docs.python.org/3/library/io.html#io.IOBase) (and its
subclasses) supports the iterator protocol, meaning that an
[IOBase](https://docs.python.org/3/library/io.html#io.IOBase) object can
be iterated over yielding the lines in a stream. Lines are defined
slightly differently depending on whether the stream is a binary stream
(yielding bytes), or a text stream (yielding character strings). See
[readline()](https://docs.python.org/3/library/io.html#io.IOBase.readline)
below.
and then in the [documentation for
`readlines`](https://docs.python.org/3/library/io.html#io.IOBase.readlines):
>Read and return a list of lines from the stream. hint can be specified
to control the number of lines read: no more lines will be read if the
total size (in bytes/characters) of all lines so far exceeds hint. [...]
>Note that it’s already possible to iterate on file objects using for
line in file: ... without calling file.readlines().
I believe that a careful reading of our [versioning
policy](https://docs.astral.sh/ruff/versioning/#version-changes)
requires that this change be deferred to a minor release - but please
correct me if I'm wrong!
This PR collects all behavior gated under preview into a new module
`ruff_linter::preview` that exposes functions like
`is_my_new_feature_enabled` - just as is done in the formatter crate.
