bug#24305: 25.1; dired can't replace '\n' in file content (dired-do-find-regexp-and-replace)

bug#24305: 25.1; dired can't replace '\n' in file content (dired-do-find-regexp-and-replace)

[Max Canal]

In GNU Emacs 25.1.2 (x86_64-unknown-linux-gnu)
 of 2016-08-15 built on blackbox
Repository revision: 8d681476bd44a2f843030579a5bbf5a248488afb
System Description:	Trisquel GNU/Linux 7.0, Belenos

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  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

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Description:
Trying to replace '\n' (inserted with C-q C-j) in Dired mode with Q
(dired-do-find-regexp-and-replace) does not work anymore. 
This was tested in v25.1.2 (rc2) with -Q flag

Good luck with that, let me know if you need more infos! :)

bug#24305: 25.1; dired can't replace '\n' in file content (dired-do-find-regexp-and-replace)

[Tino Calancha]

Thank you for the report.

As reported in NEWS file, since Emas 25.1 the key 'Q' is bound
to a new command 'dired-do-find-regexp-and-replace'.  The key 'A'
is also bound to a new command: dired-do-find-regexp.

The old commands use Emacs regexp engine, while the new commands
use grep: this may cause that regexps which previously
matched results, with the new commands don't match anymore.

That seems the case in your example: the old command matches '\n', but
the new one cannot:
;; old command
(let ((file "/tmp/bug24305/file"))
   (with-temp-file file
     (insert "\n"))
   (dired-other-window (file-name-directory file))
   (dired-goto-file file)
   (when (null (dired-do-search "\n"))
     (message "Found new line!")))

;; new command
(let ((file "/tmp/bug24305/file"))
   (with-temp-file file
     (insert "\n"))
   (dired-other-window (file-name-directory file))
   (dired-goto-file file)
   (save-excursion (dired-mark 1))
   (dired-do-find-regexp "\n"))

In your example, 'dired-do-find-regexp-and-replace' internally builds
the following `find' command (using `xref--rgrep-command'):
find /tmp/bug24305  -type f \( -iname file \) -exec grep --color -i -nH -e 
'\n' {} +

As you have noticed, this command fails.
Following commands would work:
find /tmp/bug24305  -type f \( -iname file \) -exec grep --color -i -nH -e 
'^$' {} +
find /tmp/bug24305  -type f \( -iname file \) -exec  grep --color -i -nH 
-e '
' {} +

Maybe `xref--rgrep-command' might be updated to account for this?

In the meantime, as a temporary solution, you might wish to restore the
previous bindings.  For instance, adding following in your .emacs file:
(require 'dired-aux)
(define-key dired-mode-map "A" 'dired-do-search)
(define-key dired-mode-map "Q" 'dired-do-query-replace-regexp)

Tino

bug#24305: 25.1; dired can't replace '\n' in file content (dired-do-find-regexp-and-replace)

[Eli Zaretskii]

> From: Tino Calancha <tino.calancha@gmail.com>
> Date: Thu, 25 Aug 2016 14:35:52 +0900 (JST)
> Cc: mc.maxcanal@gmail.com, dgutov@yandex.ru, tino.calancha@gmail.com
> 
> As reported in NEWS file, since Emas 25.1 the key 'Q' is bound
> to a new command 'dired-do-find-regexp-and-replace'.  The key 'A'
> is also bound to a new command: dired-do-find-regexp.
> 
> The old commands use Emacs regexp engine, while the new commands
> use grep: this may cause that regexps which previously
> matched results, with the new commands don't match anymore.
> 
> That seems the case in your example: the old command matches '\n', but
> the new one cannot:

The doc string says:

  REGEXP should use constructs supported by your local ‘grep’ command.

IOW, the '\n' should be replaced by something Grep supports, like $ or
some such (I don't think I understand the exact use case to give a
100% accurate advice).

In any case, this is a duplicate of bug#23426, which see (well, the
beginning, before the discussion went haywire).