bug#19710: 24.4.51; Isearch is broken in comints which relly on regexp

[Juri Linkov <juri@linkov.net>]

> Recent changes to commit to allow for multiline search assume fields
> throughout. The common case when comint-use-prompt-regexp is non-nil is
> not captured.
>
> To see the problem start shell and issue a couple of commands. Then
> (setq comint-use-prompt-regexp t), and add a couple of RETs. Then try M-r.
>
> You should see "Regexp history I-search backward:" several lines above
> where it should be and isearch will not work as expected.
>
> If you restart your shell, you will not even see the "Regexp history
> I-search backward:" as there are no fields in the buffer.

Thanks for the report.  This can be fixed by the patch that
reverts the change of callers, and instead modifies
`comint-line-beginning-position' to support multi-line input
for both cases of comint-use-prompt-regexp = t/nil:

diff --git a/lisp/comint.el b/lisp/comint.el
index 30c4dda..1333a0b 100644
--- a/lisp/comint.el
+++ b/lisp/comint.el
@@ -1475,7 +1475,7 @@ (defun comint-history-isearch-search ()
       (or
        ;; 1. First try searching in the initial comint text
        (funcall search-fun string
-		(if isearch-forward bound (field-beginning))
+		(if isearch-forward bound (comint-line-beginning-position))
 		noerror)
        ;; 2. If the above search fails, start putting next/prev history
        ;; elements in the comint successively, and search the string
@@ -1491,7 +1491,7 @@ (defun comint-history-isearch-search ()
 			(when (null comint-input-ring-index)
 			  (error "End of history; no next item"))
 			(comint-next-input 1)
-			(goto-char (field-beginning)))
+			(goto-char (comint-line-beginning-position)))
 		       (t
 			;; Signal an error here explicitly, because
 			;; `comint-previous-input' doesn't signal an error.
@@ -1509,7 +1509,7 @@ (defun comint-history-isearch-search ()
 				      (unless isearch-forward
 					;; For backward search, don't search
 					;; in the comint prompt
-					(field-beginning))
+					(comint-line-beginning-position))
 				      noerror)))
 	       ;; Return point of the new search result
 	       (point))
@@ -1533,16 +1533,16 @@ (defun comint-history-isearch-message (&optional c-q-hack ellipsis)
     (if (overlayp comint-history-isearch-message-overlay)
 	(move-overlay comint-history-isearch-message-overlay
 		      (save-excursion
-			(goto-char (field-beginning))
+			(goto-char (comint-line-beginning-position))
 			(forward-line 0)
 			(point))
-                      (field-beginning))
+                      (comint-line-beginning-position))
       (setq comint-history-isearch-message-overlay
 	    (make-overlay (save-excursion
-			    (goto-char (field-beginning))
+			    (goto-char (comint-line-beginning-position))
 			    (forward-line 0)
 			    (point))
-                          (field-beginning)))
+                          (comint-line-beginning-position)))
       (overlay-put comint-history-isearch-message-overlay 'evaporate t))
     (overlay-put comint-history-isearch-message-overlay
 		 'display (isearch-message-prefix ellipsis isearch-nonincremental))
@@ -1563,7 +1563,7 @@ (defun comint-history-isearch-wrap ()
       (comint-goto-input (1- (ring-length comint-input-ring)))
     (comint-goto-input nil))
   (setq isearch-success t)
-  (goto-char (if isearch-forward (field-beginning) (point-max))))
+  (goto-char (if isearch-forward (comint-line-beginning-position) (point-max))))
 
 (defun comint-history-isearch-push-state ()
   "Save a function restoring the state of input history search.
@@ -1787,7 +1787,10 @@ (defun comint-send-input (&optional no-newline artificial)
       (widen)
       (let* ((pmark (process-mark proc))
              (intxt (if (>= (point) (marker-position pmark))
-                        (progn (if comint-eol-on-send (goto-char (field-end)))
+                        (progn (if comint-eol-on-send
+				   (if comint-use-prompt-regexp
+				       (end-of-line)
+				     (goto-char (field-end))))
                                (buffer-substring pmark (point)))
                       (let ((copy (funcall comint-get-old-input)))
                         (goto-char pmark)
@@ -2266,6 +2269,7 @@ (defun comint-line-beginning-position ()
   (if comint-use-prompt-regexp
       ;; Use comint-prompt-regexp
       (save-excursion
+	(re-search-backward (concat comint-prompt-regexp ".*") nil t)
 	(beginning-of-line)
 	(comint-skip-prompt)
 	(point))
@@ -2276,7 +2280,7 @@ (defun comint-line-beginning-position ()
     ;; if there are two fields on a line, then the first one is the
     ;; prompt, and the second one is an input field, and is front-sticky
     ;; (as input fields should be).
-    (constrain-to-field (line-beginning-position) (line-end-position))))
+    (constrain-to-field (field-beginning) (line-end-position))))
 
 (defun comint-bol (&optional arg)
   "Go to the beginning of line, then skip past the prompt, if any.