bug#54804: 29.0.50; zap-to-char: case sensitive for upper-case letter

[Tino Calancha <tino.calancha@gmail.com>]

Eli Zaretskii <eliz@gnu.org> writes:

>> A wishlist for the `zap-to-char' and `zap-up-to-char':
>> In interactive calls, when users input an upper-case letter then perform
>> a case-sensitive search.
>> 
>> This behavior is analog to what `isearch' does.
>
> but why does the implementation have to be so complicated?
> Isn't this just about turning off case-fold-search while searching for
> the character?  What am I missing?

The patch is moving the shared code in zap-to/zap-up-to in a
helper function.  This has 2 motivations:
- reduce the code duplication.
- define these two related functions close each other.
- separate the logic of the function to calculate the region to kill.

If you prefer, we can keep the functions in their current
locations (simple.el/misc.el) with a patch like this one:

--8<-----------------------------cut here---------------start------------->8---
diff --git a/lisp/misc.el b/lisp/misc.el
index d85f889ffd..e771d2b315 100644
--- a/lisp/misc.el
+++ b/lisp/misc.el
@@ -64,20 +64,32 @@ copy-from-above-command
 ;; Variation of `zap-to-char'.
 
 ;;;###autoload
-(defun zap-up-to-char (arg char)
+(defun zap-up-to-char (arg char &optional interactive)
   "Kill up to, but not including ARGth occurrence of CHAR.
 Case is ignored if `case-fold-search' is non-nil in the current buffer.
 Goes backward if ARG is negative; error if CHAR not found.
-Ignores CHAR at point."
+Ignores CHAR at point.
+Called interactively, do a case sensitive search if the char is an
+upper case letter."
   (interactive (list (prefix-numeric-value current-prefix-arg)
 		     (read-char-from-minibuffer "Zap up to char: "
-						nil 'read-char-history)))
-  (let ((direction (if (>= arg 0) 1 -1)))
+						nil 'read-char-history)
+                     t))
+  ;; Avoid "obsolete" warnings for translation-table-for-input.
+  (with-no-warnings
+    (if (char-table-p translation-table-for-input)
+	(setq char (or (aref translation-table-for-input char) char))))
+  (let* ((direction (if (>= arg 0) 1 -1))
+         (str (char-to-string char))
+         (upper-case (let (case-fold-search) (string-match-p "[[:upper:]]" str)))
+         (case-fold-search (if (and interactive upper-case)
+                               nil
+                             case-fold-search)))
     (kill-region (point)
 		 (progn
 		   (forward-char direction)
 		   (unwind-protect
-		       (search-forward (char-to-string char) nil nil arg)
+		       (search-forward str nil nil arg)
 		     (backward-char direction))
 		   (point)))))
 
diff --git a/lisp/simple.el b/lisp/simple.el
index eb65701803..2f3c43b9db 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -6031,21 +6031,27 @@ backward-delete-char-untabify
     ;; Avoid warning about delete-backward-char
     (with-no-warnings (delete-backward-char n killp))))
 
-(defun zap-to-char (arg char)
+(defun zap-to-char (arg char &optional interactive)
   "Kill up to and including ARGth occurrence of CHAR.
 Case is ignored if `case-fold-search' is non-nil in the current buffer.
 Goes backward if ARG is negative; error if CHAR not found.
-See also `zap-up-to-char'."
+See also `zap-up-to-char'.
+Called interactively, do a case sensitive search if the char is an
+upper case letter."
   (interactive (list (prefix-numeric-value current-prefix-arg)
 		     (read-char-from-minibuffer "Zap to char: "
-						nil 'read-char-history)))
+						nil 'read-char-history))
+               t)
   ;; Avoid "obsolete" warnings for translation-table-for-input.
   (with-no-warnings
     (if (char-table-p translation-table-for-input)
 	(setq char (or (aref translation-table-for-input char) char))))
-  (kill-region (point) (progn
-			 (search-forward (char-to-string char) nil nil arg)
-			 (point))))
+  (let* ((str (char-to-string char))
+         (upper-case (let (case-fold-search) (string-match-p "[[:upper:]]" str)))
+         (case-fold-search (if (and interactive upper-case)
+                               nil
+                             case-fold-search)))
+    (kill-region (point) (search-forward str nil nil arg))))
 
 ;; kill-line and its subroutines.
 

--8<-----------------------------cut here---------------end--------------->8---