bug#47050: 28.0.50; [PATCH] `next-error-find-buffer' does things in the wrong order

bug#47050: 28.0.50; [PATCH] `next-error-find-buffer' does things in the wrong order

[Nick Dokos]

The doc for `next-error' says:

<quote>
C-x ` normally uses the most recently started
compilation, grep, or occur buffer.  It can also operate on any
buffer with output from the M-x compile, M-x grep commands, or,
more generally, on any buffer in Compilation mode or with
Compilation Minor mode enabled, or any buffer in which
‘next-error-function’ is bound to an appropriate function.
To specify use of a particular buffer for error messages, type
C-x ` in that buffer.  You can also use the command
‘next-error-select-buffer’ to select the buffer to use for the subsequent
invocation of ‘next-error’.
</quote>

I interpreted that to mean that if I create e.g. two `grep' buffers and
rename them uniquely to `*grep*<2>' and `*grep<3>', then switching
to one or the other of them and calling `next-error' would use the hits
from that buffer. However it always uses the hits from the last-used grep
buffer and I have to change that explicitly, by calling
`next-error-select-buffer', instead of letting the current buffer
determine it.

The problem is caused by `next-error-find-buffer' which does things in
the (IMO) wrong order: it first checks for next-error-last-buffer and
then it checks for the current buffer.

Here is a patch to reverse the order:

--8<---------------cut here---------------start------------->8---
diff --git a/lisp/simple.el b/lisp/simple.el
index f8050091d5..8796b612cc 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -298,15 +298,15 @@ next-error-find-buffer
    (funcall next-error-find-buffer-function avoid-current
                                             extra-test-inclusive
                                             extra-test-exclusive)
-   ;; 2. If next-error-last-buffer is an acceptable buffer, use that.
+   ;; 2. If the current buffer is acceptable, choose it.
+   (if (next-error-buffer-p (current-buffer) avoid-current
+			    extra-test-inclusive extra-test-exclusive)
+       (current-buffer))
+   ;; 3. If next-error-last-buffer is an acceptable buffer, use that.
    (if (and next-error-last-buffer
             (next-error-buffer-p next-error-last-buffer avoid-current
                                  extra-test-inclusive extra-test-exclusive))
        next-error-last-buffer)
-   ;; 3. If the current buffer is acceptable, choose it.
-   (if (next-error-buffer-p (current-buffer) avoid-current
-			    extra-test-inclusive extra-test-exclusive)
-       (current-buffer))
    ;; 4. Look for any acceptable buffer.
    (let ((buffers (buffer-list)))
      (while (and buffers
--8<---------------cut here---------------end--------------->8---


This arose in a question on the Emacs SE:

https://emacs.stackexchange.com/questions/63807/is-there-a-way-to-get-two-separate-next-error-lists-so-i-can-bind-them-to-two-di

---------------------------------------------------------------------------


In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.25, cairo version 1.16.0)
 of 2021-03-07 built on pierrot.dokosmarshall.org
Repository revision: 997142a4ddc98158cb71bdcef58df5a24f9a9a5c
Repository branch: comint-send-input-timeout
Windowing system distributor 'Fedora Project', version 11.0.12010000
System Description: Fedora 33 (Thirty Three)

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY
INOTIFY PDUMPER PNG RSVG SOUND THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE
XIM XPM GTK3 ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
rfc822 mml mml-sec epa derived epg epg-config gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map text-property-search seq byte-opt
gv bytecomp byte-compile cconv mm-decode mm-bodies mm-encode mail-parse
rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045
ietf-drums mm-util mail-prsvr mail-utils time-date subr-x thingatpt
cl-loaddefs cl-lib iso-transl tooltip eldoc electric uniquify ediff-hook
vc-hooks lisp-float-type mwheel term/x-win x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
newcomment text-mode elisp-mode lisp-mode prog-mode register page
tab-bar menu-bar rfn-eshadow isearch easymenu timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core term/tty-colors frame
minibuffer cl-generic cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
composite charscript charprop case-table epa-hook jka-cmpr-hook help
simple abbrev obarray cl-preloaded nadvice button loaddefs faces
cus-face macroexp files window text-properties overlay sha1 md5 base64
format env code-pages mule custom widget hashtable-print-readable
backquote threads dbusbind inotify lcms2 dynamic-setting
system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit
x multi-tty make-network-process emacs)

Memory information:
((conses 16 54100 9914)
 (symbols 48 6694 1)
 (strings 32 18784 1955)
 (string-bytes 1 617945)
 (vectors 16 13356)
 (vector-slots 8 176023 12810)
 (floats 8 21 50)
 (intervals 56 235 0)
 (buffers 992 12))

-- 
Nick



-- 
Nick

bug#47050: 28.0.50; [PATCH] `next-error-find-buffer' does things in the wrong order

[Juri Linkov]

> The doc for `next-error' says:
> ...
> I interpreted that to mean that if I create e.g. two `grep' buffers and
> rename them uniquely to `*grep*<2>' and `*grep<3>', then switching
> to one or the other of them and calling `next-error' would use the hits
> from that buffer. However it always uses the hits from the last-used grep
> buffer and I have to change that explicitly, by calling
> `next-error-select-buffer', instead of letting the current buffer
> determine it.
>
> The problem is caused by `next-error-find-buffer' which does things in
> the (IMO) wrong order: it first checks for next-error-last-buffer and
> then it checks for the current buffer.

Please try the following use case:

0. emacs -Q
1. call `grep' (anywhere) that displays the *grep* buffer
2. switch to the the *grep* buffer
3. in the *grep* buffer call `occur' that displays the *Occur* buffer
   with matches from the *grep* buffer
4. switch to the *Occur* buffer
5. type C-x ` (`next-error') in the *Occur* buffer
6. type C-x ` again - it continues visiting hits from the *Occur* buffer

But with your patch the second C-x ` will stop visiting hits
from the *Occur* buffer.

bug#47050: 28.0.50; [PATCH] `next-error-find-buffer' does things in the wrong order

[Juri Linkov]

> The doc for `next-error' says:
> ...
> I interpreted that to mean that if I create e.g. two `grep' buffers and
> rename them uniquely to `*grep*<2>' and `*grep<3>', then switching
> to one or the other of them and calling `next-error' would use the hits
> from that buffer. However it always uses the hits from the last-used grep
> buffer and I have to change that explicitly, by calling
> `next-error-select-buffer', instead of letting the current buffer
> determine it.

Please try to customize 'next-error-find-buffer-function' to this value:

  (const :tag "Current buffer if next-error capable and outside navigation"
         next-error-buffer-unnavigated-current)

It provides the behavior that you described.

bug#47050: 28.0.50; [PATCH] `next-error-find-buffer' does things in the wrong order

[Lars Ingebrigtsen]

Juri Linkov <juri@linkov.net> writes:

> Please try to customize 'next-error-find-buffer-function' to this value:
>
>   (const :tag "Current buffer if next-error capable and outside navigation"
>          next-error-buffer-unnavigated-current)
>
> It provides the behavior that you described.

More information was requested, but no response was given within a
month, so I'm closing this bug report.  If the problem still exists,
please respond to this email and we'll reopen the bug report.

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