org-src: Allow editing footnote definitions

* lisp/org-src.el (org-src--element-contents-area): Make a special
  case for footnote definitions.
(org-edit-footnote-reference): New function.
* lisp/org.el (org-edit-special): Use new function.

lisp/org-src.el

@@ -271,15 +271,30 @@ which see.  BEG and END are buffer positions."
   "Return contents boundaries of ELEMENT.
 Return value is a pair (BEG . END) where BEG and END are buffer
 positions."
-  (let ((blockp (memq (org-element-type element)
-		      '(example-block export-block src-block))))
-    (cons (org-with-wide-buffer
-	   (goto-char (org-element-property :post-affiliated element))
-	   (if blockp (line-beginning-position 2) (point)))
-	  (org-with-wide-buffer
-	   (goto-char (org-element-property :end element))
-	   (skip-chars-backward " \r\t\n")
-	   (line-beginning-position (if blockp 1 2))))))
+  (let ((type (org-element-type element)))
+    (cond
+     ((eq type 'footnote-definition)
+      (cons (org-with-wide-buffer
+	     (goto-char (org-element-property :post-affiliated element))
+	     (search-forward "]"))
+	    (org-element-property :contents-end element)))
+     ((org-element-property :contents-begin element)
+      (cons (org-element-property :contents-begin element)
+	    (org-element-property :contents-end element)))
+     ((memq type '(example-block export-block src-block))
+      (cons (org-with-wide-buffer
+	     (goto-char (org-element-property :post-affiliated element))
+	     (line-beginning-position 2))
+	    (org-with-wide-buffer
+	     (goto-char (org-element-property :end element))
+	     (skip-chars-backward " \r\t\n")
+	     (line-beginning-position 1))))
+     (t
+      (cons (org-element-property :post-affiliated element)
+	    (org-with-wide-buffer
+	     (goto-char (org-element-property :end element))
+	     (skip-chars-backward " \r\t\n")
+	     (line-beginning-position 2)))))))
 
 (defun org-src--make-source-overlay (beg end edit-buffer)
   "Create overlay between BEG and END positions and return it.
@@ -662,6 +677,46 @@ If BUFFER is non-nil, test it instead."
 	      org-src-window-setup)
      (org-pop-to-buffer-same-window buffer))))
 
+(defun org-edit-footnote-reference ()
+  "Edit definition of footnote reference at point."
+  (interactive)
+  (let ((context (org-element-context)))
+    (cond ((not (and (eq (org-element-type context) 'footnote-reference)
+		     (< (point)
+			(org-with-wide-buffer
+			 (goto-char (org-element-property :end context))
+			 (skip-chars-backward " \t")
+			 (point)))))
+	   (user-error "Not on a footnote reference"))
+	  ((eq (org-element-property :type context) 'inline)
+	   (user-error "Cannot edit inline footnotes"))
+	  (t
+	   (let* ((label (org-element-property :label context))
+		  (definition
+		    (org-with-wide-buffer
+		     (org-footnote-goto-definition label)
+		     (beginning-of-line)
+		     (org-element-at-point))))
+	     (org-src--edit-element
+	      definition (format "*Edit footnote [%s]*" label)
+	      #'org-mode
+	      (lambda () (delete-region (point) (search-forward "]")))
+	      (concat
+	       (org-propertize (format "[%s]" label)
+			       'read-only "Cannot edit footnote label"
+			       'front-sticky t
+			       'rear-nonsticky t)
+	       (org-with-wide-buffer
+		(buffer-substring-no-properties
+		 (progn
+		   (goto-char (org-element-property :contents-begin definition))
+		   (skip-chars-backward " \r\t\n")
+		   (point))
+		 (org-element-property :contents-end definition))))
+	      'remote))
+	   ;; Report success.
+	   t))))
+
 (defun org-edit-table.el ()
   "Edit \"table.el\" table at point.
 

lisp/org.el

@@ -20868,6 +20868,7 @@ When in a source code block, call `org-edit-src-code'.
 When in a fixed-width region, call `org-edit-fixed-width-region'.
 When in an export block, call `org-edit-export-block'.
 When at an #+INCLUDE keyword, visit the included file.
+When at a footnote reference, call `org-edit-footnote-reference'
 On a link, call `ffap' to visit the link at point.
 Otherwise, return a user error."
   (interactive "P")
@@ -20908,15 +20909,17 @@ Otherwise, return a user error."
          (call-interactively 'org-table-edit-formulas)))
       ;; Only Org tables contain `table-row' type elements.
       (table-row (call-interactively 'org-table-edit-formulas))
-      ((example-block src-block) (org-edit-src-code))
+      (example-block (org-edit-src-code))
       (export-block (org-edit-export-block))
       (fixed-width (org-edit-fixed-width-region))
       (otherwise
-       ;; No notable element at point.  Though, we may be at a link,
-       ;; which is an object.  Thus, scan deeper.
-       (if (eq (org-element-type (org-element-context element)) 'link)
-	   (call-interactively 'ffap)
-	 (user-error "No special environment to edit here"))))))
+       ;; No notable element at point.  Though, we may be at a link or
+       ;; a footnote reference, which are objects.  Thus, scan deeper.
+       (let ((context (org-element-context element)))
+	 (case (org-element-type context)
+	   (link (call-interactively #'ffap))
+	   (footnote-reference (org-edit-footnote-reference))
+	   (t (user-error "No special environment to edit here"))))))))
 
 (defvar org-table-coordinate-overlays) ; defined in org-table.el
 (defun org-ctrl-c-ctrl-c (&optional arg)