bug#11338: 24.1.50; read-buffer-completion-ignore-case fails on one-character names

bug#11338: 24.1.50; read-buffer-completion-ignore-case fails on one-character names

[Stephen Berman]

0. emacs -Q
1. M-x customize-option RET read-buffer-completion-ignore-case RET.
   Toggle to "on", set for the current session.
2. Type `C-x b RET a', then `C-x b RET A', then `C-x b RET ahjk', then
   switch to buffer *scratch*.
3. C-x b a TAB => Emacs correctly reports: "[Complete, but not unique]"
4. TAB => *Completions* buffer contains, as expected: A a ahjk.
5. C-x k ahjk RET.
6. C-x b a TAB => Emacs incorrectly reports: "[Sole completion]".
7. C-x b A TAB => Emacs incorrectly reports: "[Sole completion]".

In contrast, if I have files named `a' and `A', set
read-file-name-completion-ignore-case to non-nil and type `C-x C-f a
TAB', the *Completions* buffer shows, as expected, both `a' and `A'.

In GNU Emacs 24.1.50.1 (i686-suse-linux-gnu, GTK+ Version 2.24.7)
 of 2012-04-18 on escher
Bzr revision: 107959 cyd@gnu.org-20120418070052-e6bm11h52qja62ue
Windowing system distributor `The X.Org Foundation', version 11.0.11004000
Configured using:
 `configure '--without-toolkit-scroll-bars' 'CFLAGS=-g''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=local
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

bug#11338: 24.1.50; read-buffer-completion-ignore-case fails on one-character names

[Lars Ingebrigtsen]

[-- Attachment #1: Type: text/plain, Size: 687 bytes --]

Stephen Berman <stephen.berman@gmx.net> writes:

> 0. emacs -Q
> 1. M-x customize-option RET read-buffer-completion-ignore-case RET.
>    Toggle to "on", set for the current session.
> 2. Type `C-x b RET a', then `C-x b RET A', then `C-x b RET ahjk', then
>    switch to buffer *scratch*.
> 3. C-x b a TAB => Emacs correctly reports: "[Complete, but not unique]"
> 4. TAB => *Completions* buffer contains, as expected: A a ahjk.
> 5. C-x k ahjk RET.
> 6. C-x b a TAB => Emacs incorrectly reports: "[Sole completion]".
> 7. C-x b A TAB => Emacs incorrectly reports: "[Sole completion]".

(This bug report unfortunately got no response at the time.)

I tried this in Emacs 28, and I got:


[-- Attachment #2: Type: image/png, Size: 30460 bytes --]

[-- Attachment #3: Type: text/plain, Size: 336 bytes --]


So I'm going to go ahead and guess that this has been fixed at some
point in the years since this was reported, and I'm closing this bug
report.  If this is still and issue, please respond to the debbugs
address, and we'll reopen.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#11338: 24.1.50; read-buffer-completion-ignore-case fails on one-character names

[Stephen Berman]

On Mon, 07 Dec 2020 18:20:48 +0100 Lars Ingebrigtsen <larsi@gnus.org> wrote:

> Stephen Berman <stephen.berman@gmx.net> writes:
>
>> 0. emacs -Q
>> 1. M-x customize-option RET read-buffer-completion-ignore-case RET.
>>    Toggle to "on", set for the current session.
>> 2. Type `C-x b RET a', then `C-x b RET A', then `C-x b RET ahjk', then
>>    switch to buffer *scratch*.
>> 3. C-x b a TAB => Emacs correctly reports: "[Complete, but not unique]"
>> 4. TAB => *Completions* buffer contains, as expected: A a ahjk.
>> 5. C-x k ahjk RET.
>> 6. C-x b a TAB => Emacs incorrectly reports: "[Sole completion]".
>> 7. C-x b A TAB => Emacs incorrectly reports: "[Sole completion]".
>
> (This bug report unfortunately got no response at the time.)
>
> I tried this in Emacs 28, and I got:

[*Completions* buffer showing both A and a]

> So I'm going to go ahead and guess that this has been fixed at some
> point in the years since this was reported, and I'm closing this bug
> report.  If this is still and issue, please respond to the debbugs
> address, and we'll reopen.

Did you follow the above recipe exactly in order?  When I do that in
master, emacs-27 and emacs-26 (all with -Q), when at step 2 I type `C-x
b RET A' buffer `a' remains the current buffer and `C-x C-b' shows no
buffer `A'.  Only if I move step 1 of the recipe to after step 2 do I
get the same thing as in your screenshot.  So I agree that the bug I
reported seems to have been fixed, but there appears to be a new bug
which wasn't present in 24.1.50 (which I don't have readily available to
test now): that it's apparently not possible with
read-buffer-completion-ignore-case non-nil to switch to a non-existing
buffer whose name differs from an existing buffer only in case.  If you
confirm, I'll report a new bug.  Or is this considered expected behavior
(and if so, why)?

Steve Berman

bug#11338: 24.1.50; read-buffer-completion-ignore-case fails on one-character names

[Lars Ingebrigtsen]

Stephen Berman <stephen.berman@gmx.net> writes:

> Did you follow the above recipe exactly in order?

No, it's impossible to create the "A" buffer in Emacs now, apparently.

> So I agree that the bug I reported seems to have been fixed, but there
> appears to be a new bug which wasn't present in 24.1.50 (which I don't
> have readily available to test now): that it's apparently not possible
> with read-buffer-completion-ignore-case non-nil to switch to a
> non-existing buffer whose name differs from an existing buffer only in
> case.  If you confirm, I'll report a new bug.

Yup, that's how Emacs behaves now.

> Or is this considered expected behavior (and if so, why)?

I've never used that variable before, and the behaviour was unexpected
to me, but I don't know what people who do use it expect.  It's pretty
odd, though -- the variable is about completion, but Emacs now seems to
interpret it as "Emacs should ignore all case differences in buffer
names (interactively)", which is something slightly different.

So I think opening a new bug report here would make sense, and we can
gather feedback on whether this makes sense or not.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#11338: 24.1.50; read-buffer-completion-ignore-case fails on one-character names

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Tue, 08 Dec 2020 14:57:34 +0100
> Cc: 11338@debbugs.gnu.org
> 
> I've never used that variable before, and the behaviour was unexpected
> to me, but I don't know what people who do use it expect.  It's pretty
> odd, though -- the variable is about completion, but Emacs now seems to
> interpret it as "Emacs should ignore all case differences in buffer
> names (interactively)", which is something slightly different.

RET in the minibuffer invokes completion, doesn't it?

bug#11338: 24.1.50; read-buffer-completion-ignore-case fails on one-character names

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

>> I've never used that variable before, and the behaviour was unexpected
>> to me, but I don't know what people who do use it expect.  It's pretty
>> odd, though -- the variable is about completion, but Emacs now seems to
>> interpret it as "Emacs should ignore all case differences in buffer
>> names (interactively)", which is something slightly different.
>
> RET in the minibuffer invokes completion, doesn't it?

Not usually.  Try

emacs -Q
C-x b *Me RET

You'll get a buffer called "*Me" without that being completed to
"*Messages*".

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#11338: 24.1.50; read-buffer-completion-ignore-case fails on one-character names

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: stephen.berman@gmx.net,  11338@debbugs.gnu.org
> Date: Tue, 08 Dec 2020 17:21:20 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > RET in the minibuffer invokes completion, doesn't it?
> 
> Not usually.  Try
> 
> emacs -Q
> C-x b *Me RET
> 
> You'll get a buffer called "*Me" without that being completed to
> "*Messages*".

But if I do

  emacs -Q
  C-x b
  C-h c RET

Emacs says that RET runs the command minibuffer-complete-and-exit.

bug#11338: 24.1.50; read-buffer-completion-ignore-case fails on one-character names

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

>> emacs -Q
>> C-x b *Me RET
>> 
>> You'll get a buffer called "*Me" without that being completed to
>> "*Messages*".
>
> But if I do
>
>   emacs -Q
>   C-x b
>   C-h c RET
>
> Emacs says that RET runs the command minibuffer-complete-and-exit.

It does, but...  it doesn't.  :-)  RET is different from TAB RET, at
least in the *Messages* case.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no