org-element: Change return value for element at point in some corner cases

* lisp/org-element.el (org-element-at-point): When point is before any
  element, in the first blank lines of the buffer, return nil.  When
  point is within blank lines just after a headline, return that
  headline.
(org-element-context): Return nil when point is within the blank at
the beginning of the buffer.
* testing/lisp/test-org-element.el: Add tests.

lisp/org-element.el

@@ -4529,7 +4529,8 @@ As a special case, if point is at the very beginning of a list or
 sub-list, returned element will be that list instead of the first
 item.  In the same way, if point is at the beginning of the first
 row of a table, returned element will be the table instead of the
-first row.
+first row.  Also, if point is within the first blank lines of
+a buffer, return nil.
 
 If optional argument KEEP-TRAIL is non-nil, the function returns
 a list of of elements leading to element at point.  The list's
@@ -4545,25 +4546,36 @@ first element of current section."
 	 (beginning-of-line)
 	 (if (not keep-trail) (org-element-headline-parser (point-max) t)
 	   (list (org-element-headline-parser (point-max) t))))
-     ;; Otherwise move at the beginning of the section containing
+     ;; Otherwise try to move at the beginning of the section
-     ;; point.
+     ;; containing point.
      (let ((origin (point))
 	   (end (save-excursion
 		  (org-with-limited-levels (outline-next-heading)) (point)))
 	   element type special-flag trail struct prevs parent)
        (org-with-limited-levels
-	(if (org-with-limited-levels (org-before-first-heading-p))
+	(if (org-before-first-heading-p) (goto-char (point-min))
-	    (goto-char (point-min))
 	  (org-back-to-heading)
 	  (forward-line)))
-       (org-skip-whitespace)
+       (skip-chars-forward " \r\t\n" origin)
        (beginning-of-line)
+       (if (looking-at "[ \t]*$")
+	   ;; If point is still at a blank line, we didn't reach
+	   ;; section beginning.  it means we started either at the
+	   ;; beginning of the buffer, before any element, or in the
+	   ;; blank area after an headline.  In the first case, return
+	   ;; a dummy `org-data' element.  In the second case, return
+	   ;; the headline.
+	   (progn (skip-chars-backward " \r\t\n")
+		  (cond ((bobp) nil)
+			(keep-trail
+			 (list (org-element-headline-parser (point-max) t)))
+			(t (org-element-headline-parser (point-max) t))))
 	 ;; Parse successively each element, skipping those ending
 	 ;; before original position.
 	 (catch 'exit
 	   (while t
-           (setq element
+	     (setq element (org-element--current-element
-		 (org-element--current-element end 'element special-flag struct)
+			    end 'element special-flag struct)
 		   type (car element))
 	     (org-element-put-property element :parent parent)
 	     (when keep-trail (push element trail))
@@ -4611,7 +4623,7 @@ first element of current section."
 		     (table (setq special-flag 'table-row struct nil))
 		     (otherwise (setq special-flag nil struct nil)))
 		   (setq end cend)
-		 (goto-char cbeg)))))))))))
+		   (goto-char cbeg))))))))))))
 
 ;;;###autoload
 (defun org-element-context (&optional element)
@@ -4619,12 +4631,13 @@ first element of current section."
 
 Return value is a list like (TYPE PROPS) where TYPE is the type
 of the element or object and PROPS a plist of properties
-associated to it.
+associated to it, or nil if point is within the first blank lines
+of the buffer.
 
 Possible types are defined in `org-element-all-elements' and
 `org-element-all-objects'.  Properties depend on element or
-object type, but always include :begin, :end, :parent
+object type, but always include `:begin', `:end', `:parent' and
-and :post-blank properties.
+`:post-blank' properties.
 
 Optional argument ELEMENT, when non-nil, is the closest element
 containing point, as returned by `org-element-at-point'.
@@ -4632,12 +4645,16 @@ Providing it allows for quicker computation."
   (org-with-wide-buffer
    (let* ((origin (point))
 	  (element (or element (org-element-at-point)))
-	  (type (car element))
+	  (type (org-element-type element))
 	  end)
+     (cond
+      ;; If point is within blank lines at the beginning of the
+      ;; buffer, return nil.
+      ((not element) nil)
       ;; Check if point is inside an element containing objects or at
       ;; a secondary string.  In that case, move to beginning of the
       ;; element or secondary string and set END to the other side.
-     (if (not (or (let ((post (org-element-property :post-affiliated element)))
+      ((not (or (let ((post (org-element-property :post-affiliated element)))
 		  (and post (> post origin)
 		       (< (org-element-property :begin element) origin)
 		       (progn (beginning-of-line)
@@ -4685,7 +4702,8 @@ Providing it allows for quicker computation."
 				   (search-forward key (line-end-position) t)
 				   (forward-char)
 				   (setq end (line-end-position))))))))
-	 element
+       element)
+      (t
        (let ((restriction (org-element-restriction type))
 	     (parent element)
 	     candidates)
@@ -4723,7 +4741,7 @@ Providing it allows for quicker computation."
 		       (setq parent object
 			     restriction (org-element-restriction object)
 			     end cend)))))))
-	   parent))))))
+	   parent)))))))
 
 (defsubst org-element-nested-p (elem-A elem-B)
   "Non-nil when elements ELEM-A and ELEM-B are nested."

testing/lisp/test-org-element.el

@@ -2661,6 +2661,15 @@ Paragraph \\alpha."
        (org-test-with-temp-text "- Para1\n- Para2\n\nPara3"
 	 (progn (forward-line 2)
 		(org-element-type (org-element-at-point))))))
+  ;; Special case: within the first blank lines in buffer, return nil.
+  (should-not (org-test-with-temp-text "\nParagraph" (org-element-at-point)))
+  ;; Special case: within the blank lines after a headline, return
+  ;; that headline.
+  (should
+   (eq 'headline
+       (org-test-with-temp-text "* Headline\n\nParagraph"
+	 (progn (forward-line)
+		(org-element-type (org-element-at-point))))))
   ;; With an optional argument, return trail.
   (should
    (equal '(paragraph center-block)
@@ -2733,7 +2742,9 @@ Paragraph \\alpha."
        (org-test-with-temp-text "Some *text with _underline_ text*"
 	 (progn
 	   (search-forward "under")
-	   (org-element-type (org-element-context (org-element-at-point))))))))
+	   (org-element-type (org-element-context (org-element-at-point)))))))
+  ;; Return nil when point is within the first blank lines.
+  (should-not (org-test-with-temp-text "\n* Headline" (org-element-context))))
 
 
 (provide 'test-org-element)