Org Pelican Literate Document

Posted by Beetle B. on Thu 19 December 2019



These variables need to be defined:

(setq opel-output-dir-name "orgpelican")
(setq opel-page-dir "/home/me/blog/content/pages/orgpelican")
(setq opel-article-dir "/home/me/blog/content/articles/orgpelican")
(setq opel-tmp-file "/tmp/")
(setq opel-no-export "noexport")

All Definitions

Here are all the function definitions.






;; Copyright (C) 2019 Mueen Nawaz

;; This software is being released with the GNU Public License, quoted
;; below.


;; Version 3, 29 June 2007

;; Copyright © 2007 Free Software Foundation, Inc. <>

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;; You should also get your employer (if you work as a programmer) or
;; school, if any, to sign a “copyright disclaimer” for the program, if
;; necessary. For more information on this, and how to apply and follow
;; the GNU GPL, see <>.

;; The GNU General Public License does not permit incorporating your
;; program into proprietary programs. If your program is a subroutine
;; library, you may consider it more useful to permit linking
;; proprietary applications with the library. If this is what you want
;; to do, use the GNU Lesser General Public License instead of this
;; License. But first, please read
;; <>.

Get the Tags of a Node

(mapcar (lambda (tag) (replace-regexp-in-string "_" " " tag)) tags)
(defun opel-get-tags ()
  "Get all tags of a heading."
  (let ((tags (org-entry-get (point) "ALLTAGS" t)))
    (when tags
      (setq tags (split-string tags ":" t)) ; Make a list of tags.

Get the Headline of a Node

(defun opel-get-headline ()
  "Get heading of a node."
  (org-get-heading t t t t))

Get the Property of a Node

(defun opel-get-property (prop-name)
  "Get a property of a node."
  (org-entry-get (point) prop-name t))

Get the Body of a Node

This gets the body of a node and all subtrees, sans the metadata.

Now in the master org file, our post could be buried deep inside some hierarchy. In the temporary org file, though, we need this post to be at the top level. The code snippet below will promote headlines until the first subchild becomes a top level node.

(defun opel-build-level-regexp (level)
  "Build the regular expression to match the number of stars in a heading."
  (mapconcat #'identity (cons "^" (make-list level "\\*")) ""))
(defun opel-get-node-text (&optional position)
  "Gets the text of the node and all subnodes under the point or at the specified position."
    (when position (goto-char position))
      (replace-regexp-in-string (opel-build-level-regexp (org-current-level)) ""
                    (buffer-substring-no-properties (point) (point-max))))))

Get the Body of All Nodes That Have a Property

We want to know which nodes in the org document are Pelican posts. So we traverse all of them looking for a particular property.

Reddit’s alphapapa suggested I use org-get-entry, but I couldn’t get it to play nice with org-element-map. Instead I used John Kitchin’s solution:

There is one problem with this solution, though. I’m not sure what the behavior would be if you have a Pelican node nested within a Pelican node. I don’t know if org-element-map will guarantee going over the top level node first, and even if it does, I suspect it will also traverse the inner node.

I also check that none of the tags is set to prevent exporting.

(defun opel-get-all-pelican-nodes ()
  "Return a list of text of all the Pelican nodes."
  (org-element-map (org-element-parse-buffer) 'headline
    (lambda (headline)
      (when (org-element-property :PELICAN_TYPE headline)
      (goto-char (org-element-property :begin headline))
          (seq-every-p (lambda (tag) (not (equal (downcase tag) opel-no-export)))

Get All Metadata of All Nodes That Have a Property

The code snippet below will extract the date, tags, etc of a post.

(defun opel-get-all-pelican-nodes-metadata ()
  "Return a list of metadata of all the Pelican nodes."
  (org-element-map (org-element-parse-buffer) 'headline
    (lambda (headline)
    (goto-char (org-element-property :begin headline))
    (when (org-entry-get (point) "PELICAN_TYPE" nil)
      (let ((title (opel-get-headline))
        (date (opel-get-property "PELICAN_DATE"))
        (type (opel-get-property "PELICAN_TYPE"))
        (status (opel-get-property "TODO"))
        (tags (opel-get-tags))
        (custom-id (opel-get-property "CUSTOM_ID"))
        (body (opel-get-node-text)))
        `((title ,title)
          (date ,date)
          (type ,type)
          (tags ,tags)
          (status ,status)
          (custom-id ,custom-id)
          (body ,body))))))))

This seems to work, but why do I get only one result? Shouldn’t PELICANTYPE be inherited by all the children? Does org-element-property not respect inheritance? Or do I have property inheritance turned off?

Yup - I have it turned off. This will be a problem if I ever turn it on. Is there an alternative?

Yup - I switched to org-entry-get where I can control inheritance. Should be robust.

Construct Post

Construct Title

(defun opel-make-post-title (post-metadata)
  "Make the title of the post."
  (format "#+TITLE: %s" (car (alist-get 'title post-metadata))))

Test It


(setq opel-posts (opel-get-all-pelican-nodes-metadata))
(opel-make-post-title (car opel-posts))

Construct Date

We would like to use Org’s date capabilities. This means an extra square bracket at each end of the string. Let’s remove those.

(substring date 1 -1)
(defun opel-make-post-date (post-metadata)
  "Make the date of the post."
  (let ((date (car (alist-get 'date post-metadata))))
    (when date
      (format "#+DATE: %s" <<remove-square-brackets-from-date-string>>))))

Construct Status

(defun opel-make-post-status (post-metadata)
  "Make the status of the post."
  (let ((status (car (alist-get 'status post-metadata))))
    (if status
    (format ":status: %s" (downcase status))
      ":status: draft")))

Construct Tags

Tags are represented as a list. This will make them into a space delimited string.

(defun opel-make-post-tags (post-metadata)
  "Make the tags of the post."
  (let* ((tag-list (car (alist-get 'tags post-metadata)))
     (tags (mapconcat 'identity tag-list ", ")))
    (if tag-list
    (format ":tags: %s" tags)

Construct Body

(defun opel-make-post-body (post-metadata)
  "Make the body of the post."
  (let ((body (car (alist-get 'body post-metadata))))
    (format "%s"
        (replace-regexp-in-string <<image-regexp>> #'opel-transform-image-link body))))

Replace Images

An image of the form:

.. image:: {static}/images/path/image.png
   :target: {static}/images/path/image.png
   :alt:  Your alt text
   :width:  200px


will be replaced with:

.. image:: {static}/images/path/image.png
   :target: {static}/images/path/image.png
   :alt: Your alt text
   :width: 200px

The assumption is that:

  1. The user does not specify a description for the link. This is purely an inline link.
  2. The master org file is in the parent directory of images.
  3. The images directory is where all the images go, and is in the STATIC_PATHS variable in the file.

I don’t recall if CAPTION is needed, but width is not.

"\\(#\\+width: \\(.*?\\)\n\\)?#\\+CAPTION:\\(.*?\\)\n\\[\\[file:\\(.*?\\)\\]\\]"
(defun opel-transform-image-link (text)
  "Convert an image link to its rst equivalent."
    (let ((text-list (split-string text "\n"))
      (width-text nil))
      (when (= (length text-list) 3)
    (setq width-text (substring (car text-list) 8))
    (setq text-list (cdr text-list)))
      (let* ((caption-text (car text-list))
         (link-text (car (cdr text-list)))
         (caption (substring caption-text 10))
         (link (substring link-text 7 -2)))
    (if width-text
        (format "\n\n#+BEGIN_EXPORT rst\n.. image:: {static}/%s\n   :target: {static}/%s\n   :alt: %s\n   :width: %s \n\n#+END_EXPORT\n\n" link link caption width-text)
      (format "\n\n#+BEGIN_EXPORT rst\n.. image:: {static}/%s\n   :target: {static}/%s\n   :alt: %s\n\n#+END_EXPORT\n\n" link link caption))))))

Construct LaTeX newcommand Formulae

Org mode has this nice capability where if I have the following in an org file:

#+LATEX_HEADER: \newcommand{..}{..}

then I can use the new command I’ve defined and Org mode will render it when I try to render any formula using the new command. So I’d like to make use of this while authoring articles.

But this is in my master org file. How do I get it into the individual org file?

I noticed that if I put a #+LATEX_HEADER in the individual org file, pandoc will not treat it appropriately when converting to rst. Or rather, it will treat it too appropriately and mark it as LaTeX which I believe Pelican ignores.

The alternative is to convert all the \newcommand statements to $\newcommand{...}{...}$ commands and put this on top of the post.

I tried this, and got a new problem: When showing the summaries on the main page, the summary shows all these \newcommand statements. If I have a bunch of them, the summary doesn’t show anything of my actual content!

Finally I decided to put it in the header under a display:none style. I do this by creating a metadata field called newcommands and dump the LaTeX in there. My HTML template looks for this and populates it.

I have to say of all the features I put in here, this gave me the biggest headaches.

There is one major downside to my solution: We will have every newcommand in every article - even ones that don’t involve math. This means MathJax in every article. This is a poor solution, but it does the job and I don’t want to overengineer.

The code is below. A word about all the backslashes. I’m going to put this into its own org file under an EXPORT block. Then pandoc exports it to rst. Then Pelican handles it. It seems Pelican doesn’t escape the backslash when converting to HTML. So I need to ensure every backslash is escaped.

Believe it or not, the Elisp code is simply stating that one should replace one backslash with two. Even though the code has 4 and 8. Elisp is annoying that way.

(defun opel-filter-newcommand (element)
  "Given an Org keyword, filter for LATEX_HEADERs with newcommand. Then replace a backslash with two backslashes."
  (let ((key (org-element-property :key element))
    (value (org-element-property :value element)))
    (when (and (equal key "LATEX_HEADER")
           (string-match-p "newcommand" value))
      (replace-regexp-in-string "\\\\" "\\\\\\\\" value))))

(defun opel-get-newcommands ()
  "Return a list of all the \newcommand statements I have as
  (org-element-map (org-element-parse-buffer 'element) 'keyword

(defun opel-make-newcommands ()
  (format ":newcommands: %s"
      (mapconcat (lambda (x) (format "\\\\(%s\\\\)" x)) (opel-get-newcommands) "")))

Construct the Whole Post

(defun opel-make-post (post-metadata)
  "Create the full text of a post."
  (let ((body (opel-make-post-body post-metadata))
    (title (opel-make-post-title post-metadata))
    (date (opel-make-post-date post-metadata))
    (status (opel-make-post-status post-metadata))
    (tags (opel-make-post-tags post-metadata))
    (newcommands (opel-make-newcommands)))
     "%s\n%s\n#+BEGIN_EXPORT rst\n%s\n%s\n%s\n\n#+END_EXPORT\n\n%s\n"
     title date tags status newcommands body)))

Convert Post to Restructured Text

I will use Pandoc for this.

pandoc -s -f org -t rst
(defun opel-convert-post-to-rst (post-string filename)
  "Convert the string of the post to restructured text."
  (with-temp-file filename
    (insert post-string))
  (shell-command-to-string (format "<<pandoc-command>> %s" filename)))

Clean Up Math Directives

When your post has mathematics in it, pandoc will insert the following after the metadata:

.. role:: math(raw)
   :format: html latex

But there’s a problem with this. Since I put the tags and status metadata as an export block, pandoc will insert the LaTeX directive before the tags and status metadata. So you end up with:


:Date:   2018-09-30 Sun

.. role:: math(raw)
   :format: html latex

:tags: jeddah, jeddahtrip
:status: hidden

Rest of content

Now I don’t know if this leads to an invalid rst file, but Pelican doesn’t handle that well - it doesn’t see the status or tags.

I’ve noticed that if I delete the directive text, it still renders mathematics just fine. I know I have a render_math plugin - I wonder if that is helping? In any case, I want to just delete the text.

(defun opel-remove-math-directive (s)
   ".. role:: math(raw)\n   :format: html latex\n..\n"

Clean Up “example” Code

Perhaps my version of pandoc is old, but it suffers from two problems.

  1. It converts BEGIN_EXAMPLE blocks into code blocks with language example.
  2. It converts random stuff like RESULTS blocks to code blocks with the language example.

In both cases, Pygments fails.

(defun opel-fix-example-blocks (s)
   ".. code::"
   ".. code::"

Write Post to File

I have two choices: The functional approach would be to construct all the posts, and then write them one by one to a file. For a large .org file, this may consume too much RAM, and also has the down side of not writing anything if one post is malformed. Instead, I’ll construct and write before proceeding to the next post.

There is a lazy library, but for now I’ll minimize the dependencies.

(defun opel-write-post-to-file (post-string filename)
  "Write a post (in rst) to file."
  (with-temp-file filename
    (insert post-string)))

Write All Posts To Files

Find Files in Directory

Return the full path of all files, conveniently omitting “.” and “..”, and anything else that is a directory.

(defun opel-list-files (directory)
  "List all files in a directory."
   (directory-files directory t)))

Delete All Files In Directory

(defun opel-delete-files (file-list)
  "Delete all files in the list."
  (mapc #'delete-file file-list))

Write All Posts To rst Files

So the method for internal links is to use the CUSTOMID property. In Org Mode, a link of the type:

\[\[#ref-to-other-headline][link text]]

will link to the node whose CUSTOM_ID property is ref-to-other-headline.

To solve this problem, I go through all the posts that have a CUSTOM_ID property set, and make that the keys of an association list. The corresponding value is the index of the post (where it is in the list).

Later, I convert all links to link to rst#.rst where # is the index of the post being linked to.

First, make a mapping from custom-id to the index and the type. We need to know if what we’re linking to is an article or a page.

(defun opel-construct-customid-mapping (posts-metadata)
  "Create a mapping from custom-id to the index and post type."
  (let ((custom-ids)
    (indices (number-sequence 0 (length posts-metadata)))
    (mapping '()))
    (setq custom-ids (mapcar
              (lambda (post) (car (alist-get 'custom-id post)))
    (setq types (mapcar
         (lambda (post) (car (alist-get 'type post)))
    (mapcar* #'list custom-ids indices types)))
(defun opel-sub-internal-link-with-text (matched-text mapping)
  "Convert \[\[#blah][text]] to the appropriate link for Pelican."
  ;; matched-text is the matched text. I could not figure out a way to
  ;; use capture and have the function return the value based on
  ;; captured data, so I had to do some parsing on my own.

  ;; Split on ][. The left side will then be the custom-id, beginning
  ;; with [[. The right side will be the link text, ending in ]].

  ;; Also, I need the ~save-match-data~ because apparently
  ;; ~split-string~ messes up the match information. I spent hours
  ;; debugging this.
  (let* ((splitted (save-match-data (split-string matched-text "\\]\\[")))
     (custom-id (substring (car splitted) 3)) ; Omit the first \[\[#
     (link-text (substring (car (cdr splitted)) 0 -2)) ; Omit the ending ]]
     (index (car (cdr (assoc custom-id mapping))))
     (type (car (cdr (cdr (assoc custom-id mapping))))))
    ;; I need to know the type to know whether to link to a page or an article.
    (format "[[file:{filename}/%ss/%s/rst%d.rst][%s]]"

(defun opel-sub-internal-link-wo-text (matched-text mapping)
  "Convert \[\[#blah]] to the appropriate link for Pelican."
  (let* ((custom-id (substring (car splitted) 2 -2))
     (index (car (cdr (assoc custom-id mapping))))
     (type (car (cdr (cdr (assoc custom-id mapping))))))
    (format "[[file:{filename}/%ss/%s/rst%d.rst]]"

Below is the regular expression to match the long link style:


Below is the regular expression to match the short link style:

(defun opel-fix-internal-links (post-text custom-id mapping)
  "Convert internal links to point to the appropriate rst file."
  (let ((index (car (cdr (assoc custom-id mapping)))))
    (when index
      (setq post-text
         (lambda (text) (opel-sub-internal-link-with-text text mapping))
         post-text nil 't))
      (setq post-text
         (lambda (text) (opel-sub-internal-link-wo-text text mapping))
         post-text nil t)))
(defun opel-write-files-to-rst (posts-metadata)
  "Create a rst file per post and put it in the output directory."
  (opel-delete-files (opel-list-files opel-page-dir))
  (opel-delete-files (opel-list-files opel-article-dir))
  (let ((counter 0)
    (basename "rst")
    (mapping (opel-construct-customid-mapping posts-metadata)))
    (dolist (post-metadata posts-metadata)
      (let ((type (downcase (car (alist-get 'type post-metadata))))
        (directory nil)
        (post (opel-make-post post-metadata))
        (custom-id (car (alist-get 'custom-id post-metadata))))
    (cond ((equal type "page") (setq directory opel-page-dir))
          ((equal type "article") (setq directory opel-article-dir)))
    (if directory
          (setq filename (format "%s%d.rst" basename counter))
          (setq filename (concat (file-name-as-directory directory) filename))
          (setq post (opel-fix-internal-links post custom-id mapping))
         (opel-convert-post-to-rst post opel-tmp-file)))
          (setq counter (1+ counter)))
      (error "Could not determine the type of the post. Is PELICAN_TYPE set?"))))))

(defun opel-export ()
  "Export all posts."
  (setq opel-posts-metadata (opel-get-all-pelican-nodes-metadata))
  (opel-write-files-to-rst opel-posts-metadata))