From dd67ebfa2366ba5a275886c7c68f96643c59280b Mon Sep 17 00:00:00 2001
From: Achim Gratz <Stromeko@Stromeko.DE>
Date: Sat, 12 Jan 2013 11:50:27 +0100
Subject: [PATCH 3/3] org.el: advice around require to defuse mixed-install
 scenario

* lisp/org.el (require-reloads-when-shadowed): Advice around require
  to check and correct for the situation where some parts of Org have
  already been loaded, then the load-path has been changed and Org is
  now about to be activated.  To do this, unload the previously loaded
  feature named "org", "ob" or starting with "org-" or "ob-" so that
  the original require function does load the requested feature from
  the current load-path.  Move some requires up in the file so that
  the advice can be removed as early as possible.
---
 lisp/org.el | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/lisp/org.el b/lisp/org.el
index e979b35..e94442d 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -78,8 +78,35 @@ (defvar org-table-formula-constants-local nil
 (require 'find-func)
 (require 'format-spec)
 
+;; some parts of Org might already have been used from a different
+;; place, try to reload these parts from the current load-path
+(require 'loadhist)
+(defadvice require (before org-require-reload-when-shadowed
+			   (feature &optional filename noerror)
+			   activate compile preactivate)
+  "Check whether a required feature has been shadowed by changing
+`load-path' after it has been loaded and reload that feature from
+current load-path in this case."
+  (when (featurep feature)
+    (let ((feature-name (or filename (symbol-name feature))))
+      (when (string-match "^\\(org\\|ob\\)\\(-.*\\)?$" feature-name)
+	(let ((feature-lib  (file-name-directory (or (locate-library feature-name) "")))
+	      (feature-dir  (file-name-directory (feature-file feature))))
+	  ;(message "require-reload-when shadowed %s\n\t%s\n\t%s" feature-name feature-lib feature-dir)
+	  (when (not (string= feature-lib feature-dir))
+	    (message "Reloading %s" feature-name)
+	    (unload-feature feature t)))))))
 (require 'org-macs)
 (require 'org-compat)
+(require 'org-entities)
+(require 'org-faces)
+(require 'org-list)
+(require 'org-pcomplete)
+(require 'org-src)
+(require 'org-footnote)
+;; babel
+(require 'ob)
+(eval-and-compile (ad-unadvise 'require))
 
 (let ((load-suffixes (list ".el")))
   (org-load-noerror-mustsuffix "org-loaddefs"))
@@ -4991,17 +5018,6 @@ (defvar buffer-face-mode-face)
 (require 'easymenu)
 (require 'overlay)
 
-;; (require 'org-macs) moved higher up in the file before it is first used
-(require 'org-entities)
-;; (require 'org-compat) moved higher up in the file before it is first used
-(require 'org-faces)
-(require 'org-list)
-(require 'org-pcomplete)
-(require 'org-src)
-(require 'org-footnote)
-
-;; babel
-(require 'ob)
 
 ;;;###autoload
 (define-derived-mode org-mode outline-mode "Org"
-- 
1.8.1