bug#24962: 26.0.50; list-buffers doesn't show buffers w/ name " "... visiting a file

bug#24962: 26.0.50; list-buffers doesn't show buffers w/ name " "... visiting a file

[Tino Calancha]

emacs -Q -eval '(write-region "foo" nil (expand-file-name temporary-file-directory "foo"))'
  M-: (find-file (expand-file-name temporary-file-directory "foo")) RET
  M-: (rename-buffer " foo") RET
  C-x C-b
  ;; Buffer " foo" not listed.

From the Emacs manual:
doc/lispref/buffers.texi (Buffer Names):
Buffers that are ephemeral and generally uninteresting to the user
have names starting with a space, so that the @code{list-buffers} and
@code{buffer-menu} commands don't mention them (but if such a buffer
visits a file, it @strong{is} mentioned).

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
From 5f86fb83f6dcb65a3cbb03b3a09306f0375deb5a Mon Sep 17 00:00:00 2001
From: Tino Calancha <tino.calancha@gmail.com>
Date: Fri, 18 Nov 2016 20:07:15 +0900
Subject: [PATCH] List buffers with name starting with " " if they visit a file

* lisp/buff-menu.el (list-buffers--refresh)
---
  lisp/buff-menu.el | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lisp/buff-menu.el b/lisp/buff-menu.el
index 4742628..2949409 100644
--- a/lisp/buff-menu.el
+++ b/lisp/buff-menu.el
@@ -633,7 +633,8 @@ list-buffers--refresh
  	       (file buffer-file-name))
  	  (when (and (buffer-live-p buffer)
  		     (or buffer-list
-			 (and (not (string= (substring name 0 1) " "))
+			 (and (or (not (string= (substring name 0 1) " "))
+                                  file)
  			      (not (eq buffer buffer-menu-buffer))
  			      (or file show-non-file))))
  	    (push (list buffer
-- 
2.10.2

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
In GNU Emacs 26.0.50.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.3)
  of 2016-11-16
Repository revision: 6653bb45d3697c9372cc77773c49f52399740b51

bug#24962: 26.0.50; list-buffers doesn't show buffers w/ name " "... visiting a file

[Tino Calancha]

Tino Calancha <tino.calancha@gmail.com> writes:

> emacs -Q -eval '(write-region "foo" nil (expand-file-name temporary-file-directory "foo"))'
>  M-: (find-file (expand-file-name temporary-file-directory "foo")) RET
>  M-: (rename-buffer " foo") RET
>  C-x C-b
>  ;; Buffer " foo" not listed.
The order in expand-file-name arguments is inverted;  it should be:
(expand-file-name "foo" temporary-file-directory)

bug#24962: 26.0.50; list-buffers doesn't show buffers w/ name " "... visiting a file

[Eli Zaretskii]

> From: Tino Calancha <tino.calancha@gmail.com>
> Date: Fri, 18 Nov 2016 20:15:52 +0900 (JST)
> Cc: Tino Calancha <tino.calancha@gmail.com>
> 
> emacs -Q -eval '(write-region "foo" nil (expand-file-name temporary-file-directory "foo"))'
>   M-: (find-file (expand-file-name temporary-file-directory "foo")) RET
>   M-: (rename-buffer " foo") RET
>   C-x C-b
>   ;; Buffer " foo" not listed.
> 
> >From the Emacs manual:
> doc/lispref/buffers.texi (Buffer Names):
> Buffers that are ephemeral and generally uninteresting to the user
> have names starting with a space, so that the @code{list-buffers} and
> @code{buffer-menu} commands don't mention them (but if such a buffer
> visits a file, it @strong{is} mentioned).

Thank.  Please add a test for this to the test suite.

bug#24962: 26.0.50; list-buffers doesn't show buffers w/ name " "... visiting a file

[Clément Pit--Claudel]

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On 2016-11-18 09:31, Eli Zaretskii wrote:
>> From: Tino Calancha <tino.calancha@gmail.com>
>> Date: Fri, 18 Nov 2016 20:15:52 +0900 (JST)
>> Cc: Tino Calancha <tino.calancha@gmail.com>
>>
>> emacs -Q -eval '(write-region "foo" nil (expand-file-name temporary-file-directory "foo"))'
>>   M-: (find-file (expand-file-name temporary-file-directory "foo")) RET
>>   M-: (rename-buffer " foo") RET
>>   C-x C-b
>>   ;; Buffer " foo" not listed.
>>
>> >From the Emacs manual:
>> doc/lispref/buffers.texi (Buffer Names):
>> Buffers that are ephemeral and generally uninteresting to the user
>> have names starting with a space, so that the @code{list-buffers} and
>> @code{buffer-menu} commands don't mention them (but if such a buffer
>> visits a file, it @strong{is} mentioned).
> 
> Thank.  Please add a test for this to the test suite.

Could we fix the manual instead? Or do we have evidence that all modes that use temporary buffers visiting files set buffer-file-name to nil to prevent these buffers from being listed?

Clément.


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bug#24962: 26.0.50; list-buffers doesn't show buffers w/ name " "... visiting a file

[Eli Zaretskii]

> From: Clément Pit--Claudel <clement.pit@gmail.com>
> Date: Fri, 18 Nov 2016 11:48:07 -0500
> 
> >> >From the Emacs manual:
> >> doc/lispref/buffers.texi (Buffer Names):
> >> Buffers that are ephemeral and generally uninteresting to the user
> >> have names starting with a space, so that the @code{list-buffers} and
> >> @code{buffer-menu} commands don't mention them (but if such a buffer
> >> visits a file, it @strong{is} mentioned).
> > 
> > Thank.  Please add a test for this to the test suite.
> 
> Could we fix the manual instead? Or do we have evidence that all modes that use temporary buffers visiting files set buffer-file-name to nil to prevent these buffers from being listed?

I'm not sure what use case you have in mind.  Usually, temporary
buffers don't visit files, those files are inserted into temporary
buffers without affecting buffer-file-name.  But maybe you are talking
about some scenario I'm missing.

bug#24962: 26.0.50; list-buffers doesn't show buffers w/ name " "... visiting a file

[Tino Calancha]

Clément Pit--Claudel <clement.pit@gmail.com> writes:

> Could we fix the manual instead? Or do we have evidence that all modes
> that use temporary buffers visiting files set buffer-file-name to nil
> to prevent these buffers from being listed?
They shouln't automatically set `buffer-file-name', that is up to the
user.  Indeed, as Eli said, temporary buffers has such variable set to nil.

Ibuffer doesn't show the buffer ' foo' visiting a file by default.
Well, that is customizable using `ibuffer-maybe-show-predicates'.
A prefix argument in `ibuffer-update' toggle this variable.

One user might intentionally or accidentaly change the name
of a buffer visiting a file.  If we don't show it in `list-buffers'
the user might believe that the file has being deleted.
IMO one buffer visiting a file is always relevant; it's better if
we show it.

bug#24962: 26.0.50; list-buffers doesn't show buffers w/ name " "... visiting a file

[Clément Pit--Claudel]

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On 2016-11-18 12:09, Eli Zaretskii wrote:
>> From: Clément Pit--Claudel <clement.pit@gmail.com>
>> Date: Fri, 18 Nov 2016 11:48:07 -0500
>>
>>>> >From the Emacs manual:
>>>> doc/lispref/buffers.texi (Buffer Names):
>>>> Buffers that are ephemeral and generally uninteresting to the user
>>>> have names starting with a space, so that the @code{list-buffers} and
>>>> @code{buffer-menu} commands don't mention them (but if such a buffer
>>>> visits a file, it @strong{is} mentioned).
>>>
>>> Thank.  Please add a test for this to the test suite.
>>
>> Could we fix the manual instead? Or do we have evidence that all modes that use temporary buffers visiting files set buffer-file-name to nil to prevent these buffers from being listed?
> 
> I'm not sure what use case you have in mind.  Usually, temporary
> buffers don't visit files, those files are inserted into temporary
> buffers without affecting buffer-file-name.  But maybe you are talking
> about some scenario I'm missing.

Just a vague worry; no special scenario.


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bug#24962: 26.0.50; list-buffers doesn't show buffers w/ name " "... visiting a file

[Tino Calancha]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Tino Calancha <tino.calancha@gmail.com>
>> Date: Fri, 18 Nov 2016 20:15:52 +0900 (JST)
>> Cc: Tino Calancha <tino.calancha@gmail.com>
>> 
>> emacs -Q -eval '(write-region "foo" nil (expand-file-name temporary-file-directory "foo"))'
>>   M-: (find-file (expand-file-name temporary-file-directory "foo")) RET
>>   M-: (rename-buffer " foo") RET
>>   C-x C-b
>>   ;; Buffer " foo" not listed.
>> 
>> >From the Emacs manual:
>> doc/lispref/buffers.texi (Buffer Names):
>> Buffers that are ephemeral and generally uninteresting to the user
>> have names starting with a space, so that the @code{list-buffers} and
>> @code{buffer-menu} commands don't mention them (but if such a buffer
>> visits a file, it @strong{is} mentioned).
>
> Thank.  Please add a test for this to the test suite.
I don't see further comments so i've pushed a fix to the
master branch as commit af96803.