* lisp/isearch.el (isearch-occur): Sync interactive spec with occur's

new feature in `occur-read-primary-args'.  Doc fix. 

* etc/NEWS: Add new "collect" feature of `occur'.

Fixes: debbugs:10705

3 files changed, 42 insertions, 9 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 583c86b901d..65b6e532fc8 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -965,6 +965,12 @@ Its functions and variables have been similarly renamed.
 ** Occur Edit mode applies edits made in *Occur* buffers to the
 original buffers.  It is bound to "e" in Occur mode.
 
+** When `occur' is called with the prefix argument `C-u'
+the matching strings are collected into the `*Occur*' buffer
+without line numbers.  If there are parenthesized subexpressions
+in the specified regexp, `occur' reads replacement text that
+may contain \\& and \\N whose convention follows `replace-match'.
+
 +++
 ** New global minor mode electric-pair-mode.
 When enabled, typing an open parenthesis automatically inserts the
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index eaf04e72ecd..d69231fd806 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2012-02-23  Juri Linkov  <juri@jurta.org>
+
+        * isearch.el (isearch-occur): Sync interactive spec with occur's
+        new feature in `occur-read-primary-args'.  Doc fix.  (Bug#10705)
+
 2012-02-22  Juri Linkov  <juri@jurta.org>
 
         * international/mule-cmds.el (read-char-by-name): Use \` and \'.
diff --git a/lisp/isearch.el b/lisp/isearch.el
index 27b82940043..9d69443b6a4 100644
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -1433,16 +1433,38 @@ See `isearch-query-replace' for more information."
   (isearch-query-replace delimited t))
 
 (defun isearch-occur (regexp &optional nlines)
-  "Run `occur' with regexp to search from the current search string.
-Interactively, REGEXP is the current search regexp or a quoted search
-string.  NLINES has the same meaning as in `occur'."
+  "Run `occur' using the last search string as the regexp.
+Interactively, REGEXP is constructed using the search string from the
+last search command.  NLINES has the same meaning as in `occur'.
+
+If the last search command was a word search, REGEXP is computed from
+the search words, ignoring punctuation.  If the last search
+command was a regular expression search, REGEXP is the regular
+expression used in that search.  If the last search command searched
+for a literal string, REGEXP is constructed by quoting all the special
+characters in that string."
   (interactive
-   (list
-    (cond
-     (isearch-word (word-search-regexp isearch-string))
-     (isearch-regexp isearch-string)
-     (t (regexp-quote isearch-string)))
-    (if current-prefix-arg (prefix-numeric-value current-prefix-arg))))
+   (let* ((perform-collect (consp current-prefix-arg))
+          (regexp (cond
+                   (isearch-word (word-search-regexp isearch-string))
+                   (isearch-regexp isearch-string)
+                   (t (regexp-quote isearch-string)))))
+     (list regexp
+           (if perform-collect
+               ;; Perform collect operation
+               (if (zerop (regexp-opt-depth regexp))
+                   ;; No subexpression so collect the entire match.
+                   "\\&"
+                 ;; Get the regexp for collection pattern.
+                 (isearch-done nil t)
+                 (isearch-clean-overlays)
+                 (let ((default (car occur-collect-regexp-history)))
+                   (read-string
+                    (format "Regexp to collect (default %s): " default)
+                    nil 'occur-collect-regexp-history default)))
+             ;; Otherwise normal occur takes numerical prefix argument.
+             (when current-prefix-arg
+               (prefix-numeric-value current-prefix-arg))))))
   (let ((case-fold-search isearch-case-fold-search)
         ;; Set `search-upper-case' to nil to not call
         ;; `isearch-no-upper-case-p' in `occur-1'.