Re: History for query replace pairs

[Juri Linkov <juri@jurta.org>]

> I'd rather use M-p as the default because the new behavior is IMO much
> better.  But it's really no big deal, we can switch it later.
>
> JL> Maybe this choice should be customizable?
>
> OK with me, and probably most Emacs-like :)

Then a new customizable variable `query-replace-from-to-defaults'
could define whether to show previous replacement pairs as defaults
available via M-n, or via M-p if nil:

=== modified file 'lisp/replace.el'
--- lisp/replace.el	2014-08-25 02:36:45 +0000
+++ lisp/replace.el	2014-11-04 23:04:55 +0000
@@ -54,10 +54,10 @@ (defvar query-replace-history nil
 See `query-replace-from-history-variable' and
 `query-replace-to-history-variable'.")
 
-(defvar query-replace-defaults nil
+(defvar query-replace-from-to-history nil
   "Default values of FROM-STRING and TO-STRING for `query-replace'.
-This is a cons cell (FROM-STRING . TO-STRING), or nil if there is
-no default value.")
+This is a list of cons cells (FROM-STRING . TO-STRING),
+or nil if there is no default values.")
 
 (defvar query-replace-interactive nil
   "Non-nil means `query-replace' uses the last search string.
@@ -67,6 +67,19 @@ (make-obsolete-variable 'query-replace-i
 to the minibuffer that reads the string to replace, or invoke replacements
 from Isearch by using a key sequence like `C-s C-s M-%'." "24.3")
 
+(defcustom query-replace-from-to-defaults nil
+  "Non-nil means a list of replacement pairs is available by M-n instead of M-p."
+  :group 'matching
+  :type 'boolean
+  :version "24.5")
+
+(defvar query-replace-from-to-separator
+  (propertize
+   "\0" 'display (propertize
+		  (if (char-displayable-p ?\u2192) " \u2192 " " -> ")
+		  'face 'minibuffer-prompt))
+  "String that separates FROM and TO in the default replacements.")
+
 (defcustom query-replace-from-history-variable 'query-replace-history
   "History list to use for the FROM argument of `query-replace' commands.
 The value of this variable should be a symbol; that symbol
@@ -132,11 +145,14 @@ (defun query-replace-read-from (prompt r
   (if query-replace-interactive
       (car (if regexp-flag regexp-search-ring search-ring))
     (let* ((history-add-new-input nil)
+	   (from-to-history (mapcar (lambda (from-to)
+	   		       (concat (query-replace-descr (car from-to))
+				       query-replace-from-to-separator
+				       (query-replace-descr (cdr from-to))))
+	   		     query-replace-from-to-history))
 	   (prompt
-	    (if query-replace-defaults
-		(format "%s (default %s -> %s): " prompt
-			(query-replace-descr (car query-replace-defaults))
-			(query-replace-descr (cdr query-replace-defaults)))
+	    (if from-to-history
+		(format "%s (default %s): " prompt (car from-to-history))
 	      (format "%s: " prompt)))
 	   (from
 	    ;; The save-excursion here is in case the user marks and copies
@@ -144,14 +160,29 @@ (defun query-replace-read-from (prompt r
 	    ;; That should not clobber the region for the query-replace itself.
 	    (save-excursion
 	      (if regexp-flag
-		  (read-regexp prompt nil query-replace-from-history-variable)
+		  (read-regexp prompt
+			       (if query-replace-from-to-defaults
+				   from-to-history)
+			       (if query-replace-from-to-defaults
+				   query-replace-from-history-variable
+				 'from-to-history))
 		(read-from-minibuffer
-		 prompt nil nil nil query-replace-from-history-variable
-		 (car (if regexp-flag regexp-search-ring search-ring)) t)))))
-      (if (and (zerop (length from)) query-replace-defaults)
-	  (cons (car query-replace-defaults)
+		 prompt nil nil nil
+		 (if query-replace-from-to-defaults
+		     query-replace-from-history-variable
+		   'from-to-history)
+		 (if query-replace-from-to-defaults
+		     from-to-history
+		   (car (if regexp-flag regexp-search-ring search-ring)))
+		 t)))))
+      (if (and (zerop (length from)) query-replace-from-to-history)
+	  (cons (caar query-replace-from-to-history)
+		(query-replace-compile-replacement
+		 (cdar query-replace-from-to-history) regexp-flag))
+	(let* ((to (if (string-match query-replace-from-to-separator from)
 		(query-replace-compile-replacement
-		 (cdr query-replace-defaults) regexp-flag))
+			(substring from (match-end 0)) regexp-flag)))
+	       (from (if to (substring from 0 (match-beginning 0)) from)))
 	(add-to-history query-replace-from-history-variable from nil t)
 	;; Warn if user types \n or \t, but don't reject the input.
 	(and regexp-flag
@@ -163,7 +194,11 @@ (defun query-replace-read-from (prompt r
 		((string= match "\\t")
 		 (message "Note: `\\t' here doesn't match a tab; to do that, just type TAB")))
 	       (sit-for 2)))
-	from))))
+	  (if (not to)
+	      from
+	    (add-to-history query-replace-to-history-variable to nil t)
+	    (push (cons from to) query-replace-from-to-history)
+	    (cons from to)))))))
 
 (defun query-replace-compile-replacement (to regexp-flag)
   "Maybe convert a regexp replacement TO to Lisp.
@@ -216,7 +251,7 @@ (defun query-replace-read-to (from promp
 		 nil nil nil
 		 query-replace-to-history-variable from t)))
        (add-to-history query-replace-to-history-variable to nil t)
-       (setq query-replace-defaults (cons from to))
+       (push (cons from to) query-replace-from-to-history)
        to))
    regexp-flag))