bug#73234: 30.0.91; completion-preview-mode doesn't trigger for case-insensitive capf

[Eshel Yaron via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eshel Yaron <me@eshelyaron.com> writes:

[...]

>>> If case is not important, and you're fine with completing "tes" in your
>>> example to "testSymbol", then setting completion-ignore-case to non-nil
>>> should get you there, IIUC.
>>
>> I found out the hard way that completion-ignore-case isn't something
>> that can be set as buffer-local:
>>
>> https://lists.gnu.org/archive/html/emacs-devel/2024-03/msg00302.html
>>
>> I wouldn't want to set case-insensitivity globally.
>
> I'll take a closer look at that discussion, but I'm pretty sure you can
> in fact set completion-ignore-case buffer-locally.  It works as expected
> in my quick tests, and it's done in other places in Emacs already :|

FYI, I've added a new user option completion-preview-ignore-case on the
master branch (commit f1794a17b62), which controls case sensitivity for
Completion Preview mode specifically.  This is definitely safe to set
buffer-locally.  The docstring of this new variable should hopefully
also explain exactly what's the expected behavior in this regard.


Cheers,

Eshel