Re: TAGS completion with (setq-local completion-ignore-case t)

[Eli Zaretskii <eliz@gnu.org>]

> From: Morgan Willcock <morgan@ice9.digital>
> Cc: emacs-devel@gnu.org
> Date: Sat, 09 Mar 2024 13:23:08 +0000
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Does the patch below give good results?
> >
> > diff --git a/lisp/progmodes/etags.el b/lisp/progmodes/etags.el
> > index 476037e..5976121 100644
> > --- a/lisp/progmodes/etags.el
> > +++ b/lisp/progmodes/etags.el
> > @@ -2065,7 +2065,8 @@ complete-tag
> >        (user-error "%s"
> >                    (substitute-command-keys
> >                     "No tags table loaded; try \\[visit-tags-table]")))
> > -  (let ((comp-data (tags-completion-at-point-function)))
> > +  (let ((comp-data (tags-completion-at-point-function))
> > +        (completion-ignore-case (find-tag--completion-ignore-case)))
> >      (if (null comp-data)
> >  	(user-error "Nothing to complete")
> >        (completion-in-region (car comp-data) (cadr comp-data)
> 
> I rebuilt from the latest commit on the master branch to incorporate the
> patch.  Unfortunately, I do not see any change in the result of the
> failing test case; the completion still appears to be case-sensitive.
> 
>   printf "Function IsSingle\nFunction IsString\n" > functions
>   etags --lang=none --regex='/^function[ \t]+\([0-9A-Za-z:_]+\)/\1/i' functions
>   emacs -Q --eval "(progn \
>                      (pop-to-buffer (get-buffer-create \"test\")) \
>                      (setq-local completion-ignore-case t) \
>                      (visit-tags-table \"TAGS\") \
>                      (insert \"is\") \
>                      (complete-tag) \
>                      (complete-tag))"
> 
>   # No completions.

You need to set tags-case-fold-search, not the buffer-local value of
completion-ignore-case.  That's because the commands in etags.el look
at tags-case-fold-search to decide whether they should ignore
letter-case.