Getting content of paragraph element using Org Element API

Question

I've been trying to get the content of the paragraph element unsuccessfully using org-element-contents, is there something I am missing here?

I have a org document as follows:

* world
** China
*** Music
About music
*** Dance
About dance
** Japan
*** Technology
About technology
*** Movies
About movies

The elisp code lives in the same document(sorry, :( I haven't spent proper time learning elisp yet!):

#+BEGIN_SRC emacs-lisp :exports results :results none
; https://emacs.stackexchange.com/questions/53359/org-mode-headings-to-org-table
(defun goto-header()
  (org-back-to-heading)
  (org-end-of-meta-data t)
  )

(defun create_table ()
  (let
      ((rows))
    (org-map-entries
     (lambda ()
       (let*
           ((el (org-element-at-point)))
         (let* (
                (title (org-element-property :title el))
                )
           (forward-line)
           (setq desc (org-element-contents (org-element-at-point)))
           (previous-line)
           (push (list title desc) rows))))
     "LEVEL=3"
     'tree)
    (setq rows (nreverse rows))
    (setq rows (append (list '(title topic) 'hline) rows))
    (goto-header)
    (insert (concat (orgtbl-to-orgtbl rows nil) "\n"))
    )
  )

(defun create_tables ()
  (org-map-entries #'create_table "LEVEL=2")
  )

(create_tables)
#+END_SRC

It makes the following change to the document:

* world
** China
| title   | topic |
|---------+-------|
| Music   | nil   |
| (Dance) | nil   |
*** Music
About music
*** Dance
About dance
** Japan
| title      | topic |
|------------+-------|
| Technology | nil   |
| (Movies)   | nil   |
*** Technology
About technology
*** Movies
About movies

So the next two things I want is to the paragraph text to be in the topic column and and then to remove the headings. But currently I am struggling to get the contents of the paragraph. What am I missing here?

The usecase for this is I am trying to export my elfeed-org config into nice HTML tables.

Answer 1

Normally an element is a list of the form (TYPE PROPS CONTENTS), but CONTENTS is almost never useful for the purposes of the org-element library, so org-element-at-point leaves it out. Its doc string says:

...
Return value is a list like (TYPE PROPS) where TYPE is the type
of the element and PROPS a plist of properties associated to the
element.
...

Unfortunately, the missing CONTENTS part is exactly what org-element-contents is looking for, hence the nil return value.

But the contents are implicitly specified in the PROPS that org-element-at-point returns: there are two properties :contents-begin and :contents-end that specify the buffer positions of the beginning and the end of the contents, so you can get the contents from those two with buffer-substring (or more likely, buffer-substring-no-properties - you probably don't care about any string properties). To get the values of the properties themselves, you can use org-element-property.

Putting all these things together, you can write your own function to get the contents:

(defun my/org-element-contents (element)
   "Get the contents of the partially specified 'element'
that only consists of '(TYPE PROPS)'."
   (let ((beg (org-element-property :contents-begin element))
         (end (org-element-property :contents-end element)))
     (buffer-substring-no-properties beg end)))

and using (my/org-element-contents (org-element-at-point)) instead of (org-element-contents (org-element-at-point)). You may have to manipulate the string a bit (e.g. to delete newlines) in order to add it to the table.

Answer 2

1. Create a new file input.org with following content

* world

** China

*** Music

About music

Labore non esse labore exercitation

*** Dance

About dance

Nisi sint incididunt enim

** Japan

*** Technology

About technology

Cillum duis ea magna sint elit, sunt

*** Movies

About movies

Excepteur anim consequat aliqua reprehenderit excepteur

2. Copy the following snippet to *scratch* buffer, and do M-x eval-buffer

(require 'org)
(require 'dash)

(defun lisp-table-to-org-table (lisp-table)
  (->> lisp-table
       (--map (cons "" it))
       (--tree-map
        (->> it
             substring-no-properties
             (replace-regexp-in-string "\n+" " ")
             org-trim))
       (--map (->> it
                   (-interpose "|")
                   (apply #'concat)))
       (-interpose "\n")
       (apply #'concat)
       list
       (--map (with-temp-buffer
                (org-mode)
                (save-excursion
                  (insert it))
                (org-table-align)
                (buffer-substring-no-properties (point-min) (point-max))))
       car))

(defun my-transform ()
  (interactive)
  (->>
   (org-element-map (org-element-parse-buffer) 'headline
     (lambda (h)
       (when (= (org-export-get-relative-level h nil) 2)
         (list :start (org-element-property :contents-begin h)
               :end (org-element-property :contents-end h)
               :table (-> h
                          org-element-contents
                          (org-element-map 'headline
                              (lambda (h)
                                (list (substring-no-properties
                                       (org-element-interpret-data
                                        (org-element-property :title h)))
                                      (org-element-interpret-data
                                       (org-element-contents h))))
                            nil nil 'headline)
                          lisp-table-to-org-table)))))
   reverse
   (--map
    (progn
      (goto-char (plist-get it :start))
      (delete-region (plist-get it :start)
                     (plist-get it :end))
      (insert (plist-get it :table))))))

2. C-x C-f input.org
3. Do M-x my-transform RET
4. You will see this

* world

** China

| Music | About music Labore non esse labore exercitation |
| Dance | About dance Nisi sint incididunt enim           |

** Japan

| Technology | About technology Cillum duis ea magna sint elit, sunt                |
| Movies     | About movies Excepteur anim consequat aliqua reprehenderit excepteur |