GNU bug report logs - #9678
24.0.50; ediff-inferior-compare-regions ignores user response for ediff buffer selection

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Brent Goodrick <bgoodr <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.0.50;
	ediff-inferior-compare-regions ignores user response for ediff buffer
	selection
Date: Wed, 5 Oct 2011 17:32:05 -0700

This bug report will be sent to the Free Software Foundation,
not to your local site managers!
Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your report will be posted to the bug-gnu-emacs <at> gnu.org mailing list
and the gnu.emacs.bug news group, and at http://debbugs.gnu.org.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug.  If you can, give
a recipe starting from `emacs -Q':

How to reproduce:

1. Open up three separate buffers.

2. Add the same content into all three buffers, except arrange for the
content to be different on all three buffers on one of the lines (This
is just to get a difference to run through
`ediff-inferior-compare-regions').

3. Run `ediff-buffers3' and select each of the three buffers

4. Type 'n' to go to the first difference.

5. Type '=' t run `ediff-inferior-compare-regions'

6. When prompted for "Enter the 1st buffer you want to compare",
answer with 'a'.

7. When prompted for "Enter the 2nd buffer you want to compare" ,
answer with 'c'. 

8. When prompted for "Compare currently highlighted difference
regions?" answer with 'y'.

9. Notice that the new ediff session has the region for the B buffer
and not the C buffer.

My analysis: I believe the bug is the hardcoding of 'A and 'B
buf-types in both calls to
`ediff-clone-buffer-for-current-diff-comparison' made inside the
`ediff-inferior-compare-regions' function here:

		   (ediff-clone-buffer-for-current-diff-comparison
		    bufA 'A "-Region.A-")

And here:

		   (ediff-clone-buffer-for-current-diff-comparison
		    bufB 'B "-Region.B-")

Here is a possible fixed version of the function where I introduced
the buf-type-A and buf-type-B local variables to store the 'A, 'B, or
'C symbols corresponding to the users selection, and used those values
in the calls to `ediff-clone-buffer-for-current-diff-comparison':

(defun ediff-inferior-compare-regions ()
  "Compare regions in an active Ediff session.
Like ediff-regions-linewise but is called from under an active Ediff session on
the files that belong to that session.

After quitting the session invoked via this function, type C-l to the parent
Ediff Control Panel to restore highlighting."
  (interactive)
  (let ((answer "")
	(possibilities (list ?A ?B ?C))
	(zmacs-regions t)
	use-current-diff-p
	begA begB endA endB bufA bufB buf-type-A buf-type-B)
    (if (ediff-valid-difference-p ediff-current-difference)
	(progn
	  (ediff-set-fine-diff-properties ediff-current-difference 'default)
	  (ediff-unhighlight-diff)))
    (ediff-paint-background-regions 'unhighlight)
    (flet ((char-to-buf-type (char)
			     (cond ((eq char ?A) 'A)
				   ((eq char ?B) 'B)
				   ((eq char ?C) 'C)
				   (t
				    (error "Assertion failed: invalid character %S" char)))))
      (cond ((ediff-merge-job)
	     (setq bufB ediff-buffer-C)
	     ;; ask which buffer to compare to the merge buffer
	     (while (cond ((eq answer ?A)
			   (setq bufA ediff-buffer-A
				 possibilities '(?B)
				 buf-type-B (char-to-buf-type answer))
			   nil)
			  ((eq answer ?B)
			   (setq bufA ediff-buffer-B
				 possibilities '(?A)
				 buf-type-B (char-to-buf-type answer))
			   nil)
			  ((equal answer ""))
			  (t (beep 1)
			     (message "Valid values are A or B")
			     (sit-for 2)
			     t))
	       (let ((cursor-in-echo-area t))
		 (message
		  "Which buffer to compare to the merge buffer (A or B)? ")
		 (setq answer (capitalize (read-char-exclusive))))))
	    ((ediff-3way-comparison-job)
	     ;; ask which two buffers to compare
	     (while (cond ((memq answer possibilities)
			   (setq possibilities (delq answer possibilities))
			   (setq bufA
				 (eval
				  (ediff-get-symbol-from-alist
				   answer ediff-buffer-alist)))
			   (setq buf-type-A (char-to-buf-type answer))
			   nil)
			  ((equal answer ""))
			  (t (beep 1)
			     (message
			      "Valid values are %s"
			      (mapconcat 'char-to-string possibilities " or "))
			     (sit-for 2)
			     t))
	       (let ((cursor-in-echo-area t))
		 (message "Enter the 1st buffer you want to compare (%s): "
			  (mapconcat 'char-to-string possibilities " or "))
		 (setq answer (capitalize (read-char-exclusive)))))
	     (setq answer "") ; silence error msg
	     (while (cond ((memq answer possibilities)
			   (setq possibilities (delq answer possibilities))
			   (setq bufB
				 (eval
				  (ediff-get-symbol-from-alist
				   answer ediff-buffer-alist)))
			   (setq buf-type-B (char-to-buf-type answer))
			   nil)
			  ((equal answer ""))
			  (t (beep 1)
			     (message
			      "Valid values are %s"
			      (mapconcat 'char-to-string possibilities " or "))
			     (sit-for 2)
			     t))
	       (let ((cursor-in-echo-area t))
		 (message "Enter the 2nd buffer you want to compare (%s): "
			  (mapconcat 'char-to-string possibilities "/"))
		 (setq answer (capitalize (read-char-exclusive))))))
	    (t ; 2way comparison
	     (setq bufA ediff-buffer-A
		   bufB ediff-buffer-B
		   possibilities nil))))
    (if (and (ediff-valid-difference-p ediff-current-difference)
	     (y-or-n-p "Compare currently highlighted difference regions? "))
	(setq use-current-diff-p t))
    (setq bufA (if use-current-diff-p
		   (ediff-clone-buffer-for-current-diff-comparison
		    bufA buf-type-A "-Region.A-")
		 (ediff-clone-buffer-for-region-comparison bufA "-Region.A-")))
    (ediff-with-current-buffer bufA
      (setq begA (region-beginning)
	    endA (region-end))
      (goto-char begA)
      (beginning-of-line)
      (setq begA (point))
      (goto-char endA)
      (end-of-line)
      (or (eobp) (forward-char)) ; include the newline char
      (setq endA (point)))
    (setq bufB (if use-current-diff-p
		   (ediff-clone-buffer-for-current-diff-comparison
		    bufB buf-type-B "-Region.B-")
		 (ediff-clone-buffer-for-region-comparison bufB "-Region.B-")))
    (ediff-with-current-buffer bufB
      (setq begB (region-beginning)
	    endB (region-end))
      (goto-char begB)
      (beginning-of-line)
      (setq begB (point))
      (goto-char endB)
      (end-of-line)
      (or (eobp) (forward-char)) ; include the newline char
      (setq endB (point)))
    (ediff-regions-internal
     bufA begA endA bufB begB endB
     nil     	     	     	; setup-hook
     (if use-current-diff-p	; job name
	 'ediff-regions-wordwise
       'ediff-regions-linewise)
     (if use-current-diff-p	; word mode, if diffing current diff
	 t nil)
     ;; setup param to pass to ediff-setup
     (list (cons 'ediff-split-window-function ediff-split-window-function)))))

I did not test the "ediff-merge-job" case but I suspect it also needs
to set the buf-type-A and buf-type-B variables. The 'char-to-buf-type'
local function could be written more concisely, but I could not find a
way to map a ?A character to a 'A symbol without resorting to a clunky
cond construct.


If Emacs crashed, and you have the Emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
For information about debugging Emacs, please read the file
/home/brentg/install/Linux.x86_64/share/emacs/24.0.50/etc/DEBUG.


In GNU Emacs 24.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.20.1)
 of 2011-01-15 on hungover
Windowing system distributor `The X.Org Foundation', version 11.0.10707000
configured using `configure  '--with-x-toolkit' '--with-xft' '--prefix=/home/brentg/install/Linux.x86_64''

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: nil
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Shell

Minor modes in effect:
  desktop-save-mode: t
  auto-insert-mode: t
  erc-ring-mode: t
  erc-services-mode: t
  erc-networks-mode: t
  shell-dirtrack-mode: t
  delete-selection-mode: t
  iswitchb-mode: t
  display-time-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: 1
  transient-mark-mode: t
  abbrev-mode: t

Recent input:
<return> r h y <tab> w <tab> <return> M-x r e p o r 
t - e m <tab> b <tab> <return>

Recent messages:
History item: 498
History item: 499
History item: 500
~ 
Completing command name...
Completed
Type C-x 1 to delete the help window.
mouse-2, RET: find function's definition
Renamed transient buffer "*Help*" to "*Help*<2>"
uncompressing ediff-util.el.gz...done

Load-path shadows:
/home/brentg/emacs_lisp_imported/slime/tree-widget hides /home/brentg/install/Linux.x86_64/share/emacs/24.0.50/lisp/tree-widget
/home/brentg/emacs_lisp_imported/remember/remember hides /home/brentg/install/Linux.x86_64/share/emacs/24.0.50/lisp/textmodes/remember
/home/brentg/emacs_lisp_imported/css-mode/css-mode hides /home/brentg/install/Linux.x86_64/share/emacs/24.0.50/lisp/textmodes/css-mode

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