bug#28439: suggestion: support case-independent xref-find-definitions prompt TAB

[Dmitry Gutov <dgutov@yandex.ru>]

On 9/14/17 8:01 PM, Eli Zaretskii wrote:

>> Sorry, what don't we want to follow the value of completion-ignore-case?
> 
> Because it has a much broader effect. 

I guessed so. But do you have a particular problem in mind?

> And because the issue here is
> inconsistency between completion and actual matching in
> xref-find-definitions.  They should be consistent, IMO.

I think I agree, because xref--read-identifier calls completing-read 
with nil require-match argument (so we can't rely on the completion 
table to correct the input), but your patch doesn't fix the 
inconsistency. It only moves the identifier read toward the 
case-fold-search default.

>> The fact that we have the option tags-case-fold-search (used in
>> find-tag-tag, among other places) probably means that some users prefer
>> not to ignore case.
> 
> Then maybe an alternative is to make tags-case-fold-search nil by
> default? Or make xref--read-identifier be case-insensitive if
> case-fold-search is non-nil?

The other way around: etags--xref-find-definitions can bind 
tags-case-fold-search to the value of completion-ignore-case. Or 
whichever xref-specific variable we add.

We'd also need to add case-insensitive search support to 
elisp--xref-find-definitions, I suppose. So far, 
find-function-search-for-symbol always performs case-sensitive search. 
It's rarely a problem, though, because Elisp uses capital letters very 
infrequently.

>> Maybe we could add a similar xref-specific option on top, but I'm not
>> sure why completion-ignore-case is not good enough.
>>
>> We could change its default to t, though.
> 
> Emacs-wide?  Or just when completing on identifiers?

Either is fine, as far as I'm concerned.