Introduce `xref-etags-mode'

Fixes: debbugs:19466

* lisp/progmodes/xref.el (xref-etags-mode--saved): New variable.
(xref-etags-mode): New minor mode.

2 files changed, 29 insertions, 0 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index b4c6d0be8ef..ced342baeb9 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2015-02-23  Dmitry Gutov  <dgutov@yandex.ru>
+
+        Introduce `xref-etags-mode'.
+        * progmodes/xref.el (xref-etags-mode--saved): New variable.
+        (xref-etags-mode): New minor mode.  (Bug#19466)
+
 2015-02-22  Lars Magne Ingebrigtsen  <larsi@gnus.org>
 
         * dom.el (dom-previous-sibling): New function.
diff --git a/lisp/progmodes/xref.el b/lisp/progmodes/xref.el
index 55405b63fe0..fe72b3f778c 100644
--- a/lisp/progmodes/xref.el
+++ b/lisp/progmodes/xref.el
@@ -628,6 +628,29 @@ The argument has the same meaning as in `apropos'."
 ;;;###autoload (define-key ctl-x-5-map "." #'xref-find-definitions-other-frame)
 
 
+;;; Helper functions
+
+(defvar xref-etags-mode--saved nil)
+
+(define-minor-mode xref-etags-mode
+  "Minor mode to make xref use etags again.
+
+Certain major modes install their own mechanisms for listing
+identifiers and navigation.  Turn this on to undo those settings
+and just use etags."
+  :lighter ""
+  (if xref-etags-mode
+      (progn
+        (setq xref-etags-mode--saved
+              (cons xref-find-function
+                    xref-identifier-completion-table-function))
+        (kill-local-variable 'xref-find-function)
+        (kill-local-variable 'xref-identifier-completion-table-function))
+    (setq-local xref-find-function (car xref-etags-mode--saved))
+    (setq-local xref-identifier-completion-table-function
+                (cdr xref-etags-mode--saved))))
+
+
 (provide 'xref)
 
 ;;; xref.el ends here