2 files changed, 31 insertions, 23 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 026b05a7231..81061db8759 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,9 @@
 2010-09-05  Chong Yidong  <cyd@stupidchicken.com>
 
+        * dired.el (dired-ls-sorting-switches, dired-sort-by-name-regexp):
+        Improve regexps (Bug#6987).
+        (dired-sort-toggle): Search more robustly for -t flag.
+
         * files.el (get-free-disk-space): Search more robustly for
         "available" column.  Suggested by Ehud Karni
         <ehud@unix.mvs.co.il>.
diff --git a/lisp/dired.el b/lisp/dired.el
index ecc3b5bd47e..3fdb82ca7d3 100644
--- a/lisp/dired.el
+++ b/lisp/dired.el
@@ -3249,12 +3249,16 @@ variable `dired-listing-switches'.  To temporarily override the listing
 format, use `\\[universal-argument] \\[dired]'.")
 
 (defvar dired-sort-by-date-regexp
-  (concat "^-[^" dired-ls-sorting-switches
-          "]*t[^" dired-ls-sorting-switches "]*$")
+  (concat "\\(\\`\\| \\)-[^- ]*t"
+          ;; `dired-ls-sorting-switches' after -t overrides -t.
+          "[^ " dired-ls-sorting-switches "]*"
+          "\\(\\(\\`\\| +\\)\\(--[^ ]+\\|-[^- t"
+          dired-ls-sorting-switches "]+\\)\\)* *$")
   "Regexp recognized by Dired to set `by date' mode.")
 
 (defvar dired-sort-by-name-regexp
-  (concat "^-[^t" dired-ls-sorting-switches "]+$")
+  (concat "\\`\\(\\(\\`\\| +\\)\\(--[^ ]+\\|"
+          "-[^- t" dired-ls-sorting-switches "]+\\)\\)* *$")
   "Regexp recognized by Dired to set `by name' mode.")
 
 (defvar dired-sort-inhibit nil
@@ -3280,8 +3284,8 @@ The idea is to set this buffer-locally in special dired buffers.")
     (force-mode-line-update)))
 
 (defun dired-sort-toggle-or-edit (&optional arg)
-  "Toggle between sort by date/name and refresh the dired buffer.
-With a prefix argument you can edit the current listing switches instead."
+  "Toggle sorting by date, and refresh the Dired buffer.
+With a prefix argument, edit the current listing switches instead."
   (interactive "P")
   (when dired-sort-inhibit
     (error "Cannot sort this dired buffer"))
@@ -3292,24 +3296,24 @@ With a prefix argument you can edit the current listing switches instead."
 
 (defun dired-sort-toggle ()
   ;; Toggle between sort by date/name.  Reverts the buffer.
-  (setq dired-actual-switches
-        (let (case-fold-search)
-          (if (string-match " " dired-actual-switches)
-              ;; New toggle scheme: add/remove a trailing " -t"
-              (if (string-match " -t\\'" dired-actual-switches)
-                  (substring dired-actual-switches 0 (match-beginning 0))
-                (concat dired-actual-switches " -t"))
-            ;; old toggle scheme: look for some 't' switch and add/remove it
-            (concat
-             "-l"
-             (dired-replace-in-string (concat "[-lt"
-                                              dired-ls-sorting-switches "]")
-                                      ""
-                                      dired-actual-switches)
-             (if (string-match (concat "[t" dired-ls-sorting-switches "]")
-                               dired-actual-switches)
-                 ""
-               "t")))))
+  (let ((sorting-by-date (string-match dired-sort-by-date-regexp
+                                       dired-actual-switches))
+        ;; Regexp for finding (possibly embedded) -t switches.
+        (switch-regexp "\\(\\`\\| \\)-\\([a-su-zA-Z]*\\)\\(t\\)\\([^ ]*\\)")
+        case-fold-search)
+    ;; Remove the -t switch.
+    (while (string-match switch-regexp dired-actual-switches)
+      (if (and (equal (match-string 2 dired-actual-switches) "")
+               (equal (match-string 4 dired-actual-switches) ""))
+          ;; Remove a stand-alone -t switch.
+          (setq dired-actual-switches
+                (replace-match "" t t dired-actual-switches))
+        ;; Remove a switch of the form -XtY for some X and Y.
+        (setq dired-actual-switches
+              (replace-match "" t t dired-actual-switches 3))))
+    ;; Now, if we weren't sorting by date before, add the -t switch.
+    (unless sorting-by-date
+      (setq dired-actual-switches (concat dired-actual-switches " -t"))))
   (dired-sort-set-modeline)
   (revert-buffer))