org-element: Make properties parsing more robust

* lisp/org-element.el (org-element-property-drawer-parser,
  org-element-node-property-parser): Ignore lines that are not node
  properties.
(org-element-node-property-interpreter): Allow nil properties.

* lisp/org.el (org-re-property): Fix regexp to match properties with
  empty values.

* testing/lisp/test-org-element.el (test-org-element/node-property):
  Add tests.

Thanks to Eike for reporting it.
http://permalink.gmane.org/gmane.emacs.orgmode/90293

lisp/org-element.el

@@ -1312,36 +1312,36 @@ containing `:begin', `:end', `:hiddenp', `:contents-begin',
 `:contents-end', `:post-blank' and `:post-affiliated' keywords.
 
 Assume point is at the beginning of the property drawer."
-  (save-excursion
-    (let ((case-fold-search t))
-      (if (not (save-excursion
-		 (re-search-forward "^[ \t]*:END:[ \t]*$" limit t)))
-	  ;; Incomplete drawer: parse it as a paragraph.
-	  (org-element-paragraph-parser limit affiliated)
-	(save-excursion
-	  (let* ((drawer-end-line (match-beginning 0))
-		 (begin (car affiliated))
-		 (post-affiliated (point))
-		 (contents-begin (progn (forward-line)
-					(and (< (point) drawer-end-line)
-					     (point))))
-		 (contents-end (and contents-begin drawer-end-line))
-		 (hidden (org-invisible-p2))
-		 (pos-before-blank (progn (goto-char drawer-end-line)
-					  (forward-line)
-					  (point)))
-		 (end (progn (skip-chars-forward " \r\t\n" limit)
-			     (if (eobp) (point) (line-beginning-position)))))
-	    (list 'property-drawer
-		  (nconc
-		   (list :begin begin
-			 :end end
-			 :hiddenp hidden
-			 :contents-begin contents-begin
-			 :contents-end contents-end
-			 :post-blank (count-lines pos-before-blank end)
-			 :post-affiliated post-affiliated)
-		   (cdr affiliated)))))))))
+  (let ((case-fold-search t))
+    (if (not (save-excursion (re-search-forward "^[ \t]*:END:[ \t]*$" limit t)))
+	;; Incomplete drawer: parse it as a paragraph.
+	(org-element-paragraph-parser limit affiliated)
+      (save-excursion
+	(let* ((drawer-end-line (match-beginning 0))
+	       (begin (car affiliated))
+	       (post-affiliated (point))
+	       (contents-begin
+		(progn
+		  (forward-line)
+		  (and (re-search-forward org-property-re drawer-end-line t)
+		       (line-beginning-position))))
+	       (contents-end (and contents-begin drawer-end-line))
+	       (hidden (org-invisible-p2))
+	       (pos-before-blank (progn (goto-char drawer-end-line)
+					(forward-line)
+					(point)))
+	       (end (progn (skip-chars-forward " \r\t\n" limit)
+			   (if (eobp) (point) (line-beginning-position)))))
+	  (list 'property-drawer
+		(nconc
+		 (list :begin begin
+		       :end end
+		       :hiddenp hidden
+		       :contents-begin contents-begin
+		       :contents-end contents-end
+		       :post-blank (count-lines pos-before-blank end)
+		       :post-affiliated post-affiliated)
+		 (cdr affiliated))))))))
 
 (defun org-element-property-drawer-interpreter (property-drawer contents)
   "Interpret PROPERTY-DRAWER element as Org syntax.
@@ -2096,28 +2096,28 @@ LIMIT bounds the search.
 Return a list whose CAR is `node-property' and CDR is a plist
 containing `:key', `:value', `:begin', `:end' and `:post-blank'
 keywords."
-  (save-excursion
-    (looking-at org-property-re)
-    (let ((case-fold-search t)
-	  (begin (point))
-	  (key   (org-match-string-no-properties 2))
-	  (value (org-match-string-no-properties 3))
-	  (pos-before-blank (progn (forward-line) (point)))
-	  (end (progn (skip-chars-forward " \r\t\n" limit)
-		      (if (eobp) (point) (point-at-bol)))))
-      (list 'node-property
-	    (list :key key
-		  :value value
-		  :begin begin
-		  :end end
-		  :post-blank (count-lines pos-before-blank end))))))
+  (looking-at org-property-re)
+  (let ((begin (point))
+	(key   (org-match-string-no-properties 2))
+	(value (org-match-string-no-properties 3))
+	(end (save-excursion
+	       (end-of-line)
+	       (if (re-search-forward org-property-re limit t)
+		   (line-beginning-position)
+		 limit))))
+    (list 'node-property
+	  (list :key key
+		:value value
+		:begin begin
+		:end end
+		:post-blank 0))))
 
 (defun org-element-node-property-interpreter (node-property contents)
   "Interpret NODE-PROPERTY element as Org syntax.
 CONTENTS is nil."
   (format org-property-format
 	  (format ":%s:" (org-element-property :key node-property))
-	  (org-element-property :value node-property)))
+	  (or (org-element-property :value node-property) "")))
 
 
 ;;;; Paragraph

lisp/org.el

@@ -6156,9 +6156,9 @@ Use `org-reduced-level' to remove the effect of `org-odd-levels'."
  Match group 3 will be set to the value if it exists."
    (concat "^\\(?4:[ \t]*\\)\\(?1::\\(?2:"
  	  (if literal property (regexp-quote property))
-	  "\\):\\)[ \t]+\\(?3:[^ \t\r\n]"
-	  (if allow-null "*")
-	  ".*?\\)\\(?5:[ \t]*\\)$"))
+	  "\\):\\)\\(?:[ \t]+\\(?3:[^ \t\r\n].*?\\)\\)"
+	  (and allow-null "?")
+	  "\\(?5:[ \t]*\\)$"))
 
 (defconst org-property-re
   (org-re-property ".*?" 'literal t)

testing/lisp/test-org-element.el

@@ -1479,23 +1479,37 @@ e^{i\\pi}+1=0
   ;; Standard test.
   (should
    (equal '("abc" "value")
-	  (org-test-with-temp-text ":PROPERTIES:\n:abc: value\n:END:"
-	    (progn (forward-line)
-		   (let ((element (org-element-at-point)))
-		     (list (org-element-property :key element)
-			   (org-element-property :value element)))))))
+	  (org-test-with-temp-text ":PROPERTIES:\n<point>:abc: value\n:END:"
+	    (let ((element (org-element-at-point)))
+	      (list (org-element-property :key element)
+		    (org-element-property :value element))))))
   ;; Value should be trimmed.
   (should
    (equal "value"
-	  (org-test-with-temp-text ":PROPERTIES:\n:abc: value  \n:END:"
-	    (progn (forward-line)
-		   (let ((element (org-element-at-point)))
-		     (org-element-property :value element))))))
+	  (org-test-with-temp-text ":PROPERTIES:\n<point>:abc: value  \n:END:"
+	    (org-element-property :value (org-element-at-point)))))
   ;; A node property requires to be wrapped within a property drawer.
   (should-not
    (eq 'node-property
        (org-test-with-temp-text ":abc: value"
-	 (org-element-type (org-element-at-point))))))
+	 (org-element-type (org-element-at-point)))))
+  ;; Accept empty properties.
+  (should
+   (equal '(("foo" "value") ("bar" nil))
+	  (org-test-with-temp-text ":PROPERTIES:\n:foo: value\n:bar:\n:END:"
+	    (org-element-map (org-element-parse-buffer) 'node-property
+	      (lambda (p)
+		(list (org-element-property :key p)
+		      (org-element-property :value p)))))))
+  ;; Ignore all non-property lines in property drawers.
+  (should
+   (equal
+    '(("foo" "value"))
+    (org-test-with-temp-text ":PROPERTIES:\nWrong1\n:foo: value\nWrong2\n:END:"
+      (org-element-map (org-element-parse-buffer) 'node-property
+	(lambda (p)
+	  (list (org-element-property :key p)
+		(org-element-property :value p))))))))
 
 
 ;;;; Paragraph