bug#12986: Pressing backspace during isearch exits case-sensitive and word modes

[Lars Ingebrigtsen <larsi@gnus.org>]

Juri Linkov <juri@jurta.org> writes:

>> Good point.  `isearch-delete-char' (that uses `isearch-pop-state')
>> restores word mode but not regexp mode.  This looks like
>> unaccountable inconsistency.  Perhaps it should restore
>> regexp mode as well.

[...]

> This patch adds a new user option `isearch-keep-stack-variables'
> intended to accompany another option `isearch-keep-mode-variables'
> added in bug#11378.  It adds a new option but doesn't change
> the default behavior - its default value is `isearch-regexp'
> that means to not keep regexp mode when pressing backspace
> (other search variables will be supported later as well).

I respun the patch for Emacs 28, but looking at it, I guess it doesn't
support actually restoring the modes it's discussing?

diff --git a/lisp/isearch.el b/lisp/isearch.el
index 0879f948cf..e9a3a2e921 100644
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -167,6 +167,17 @@ isearch-hide-immediately
 the search, with the exception of the last successful match, if any."
   :type 'boolean)
 
+(defcustom isearch-keep-stack-variables '(isearch-regexp)
+  "A set of search variables to keep and not to restore from the search stack."
+  :type '(set (const :tag "Regexp search" isearch-regexp)
+	      (const :tag "Case folding" isearch-case-fold-search)
+	      (const :tag "Invisible text" isearch-invisible)
+	      (const :tag "Filters" isearch-filter-predicates)
+	      (const :tag "Lax whitespace" isearch-lax-whitespace)
+	      (const :tag "Regexp lax whitespace" isearch-regexp-lax-whitespace))
+  :version "28.1"
+  :group 'isearch)
+
 (defcustom isearch-resume-in-command-history nil
   "If non-nil, `isearch-resume' commands are added to the command history.
 This allows you to resume earlier Isearch sessions through the
@@ -1515,6 +1526,7 @@ isearch-update-from-string-properties
                  (case-fold-search isearch-case-fold-search)
                  (pop-fun (if isearch-push-state-function
                               (funcall isearch-push-state-function)))
+		 (regexp isearch-regexp)
                  (match-data isearch-match-data))))
   (string nil :read-only t)
   (message nil :read-only t)
@@ -1528,6 +1540,7 @@ isearch-update-from-string-properties
   (barrier nil :read-only t)
   (case-fold-search nil :read-only t)
   (pop-fun nil :read-only t)
+  (regexp :read-only t)
   (match-data nil :read-only t))
 
 (defun isearch--set-state (cmd)
@@ -1542,6 +1555,8 @@ isearch--set-state
 	isearch-barrier (isearch--state-barrier cmd)
 	isearch-case-fold-search (isearch--state-case-fold-search cmd)
 	isearch-match-data (isearch--state-match-data cmd))
+  (unless (memq 'isearch-regexp isearch-keep-stack-variables)
+    (setq isearch-regexp (isearch--state-regexp cmd)))
   (if (functionp (isearch--state-pop-fun cmd))
       (funcall (isearch--state-pop-fun cmd) cmd))
   (goto-char (isearch--state-point cmd)))

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no