Tag Archives: Markdown

Migrating from WP-Syntax to PrismJS

WP-Syntax was a great syntax-highlighting plugin for WordPress. However, development had ceased and it was not updated for a very long time. While it is not broken per se, it didn’t work with Jetpack’s markdown support and so I stopped using it on the site and started using a different plugin. With the introduction of the Gutenberg editor, I started looking again for a plugin that will allow me to easily highlight fenced code blocks (this feature worked in the old editor with SyntaxHighlighter Evolved but isn’t supported in Gutenberg). Realizing that I don’t want three syntax-highlighting plugins enabled simultaneously, and not wanting to have an abandoned plugin enabled, I decided to migrate all the posts from WP-Syntax to a new solution.

The new solution I chose was PrismJS. I decided to use it directly (without a plugin) as it highlights by default all the <pre><code class="language-..."> constructs (which is what markdown produces as well) and I didn’t want (yet again) to use plugin specific shortcodes like before which will require migration when the plugin eventually stops working.

WP-Syntax used <pre lang="...">code goes here</pre> construct. Furthermore, it took care of html escaping everything inside the <pre> tag. So the migration solution would be to rewrite the <pre> tags to <pre><code> constructs, html escape the code inside the pre tag and finally remove any leading newlines. I wrote it to work on dumped SQL tables as it seemed easiest. The flow is

$ mysqldump --add-drop-table -u USER -p blog wp_comments > wp_posts.sql
$ python3 < wp_posts.sql > wp_posts_updated.sql
$ mysql --user=USER --password blog < /tmp/wp_posts_updated.sql

import re
import html
import sys

def convert(fin, fout):
    for line in fin:
        # Each post is in a single line
        # <pre><code> doesn't ignore the first newline like <pre>
        replaced = re.sub(r'<pre lang=\\"(.*?)\\">(?:\\r)?(?:\\n)?(.*?)</pre>', replace_and_escape, line)
        if line != replaced:
            print(line, replaced, sep="\n============>\n", file=sys.stderr)

def replace_and_escape(matchobj):
    language = matchobj.group(1)
    # We don't escape quotes because it's unnecessary and it would mess up the
    # SQL escaping
    content = html.escape(matchobj.group(2), quote=False)
    return r'<pre><code class=\"language-{}\">{}</code></pre>'.format(language, content)

if __name__=='__main__':
    convert(sys.stdin, sys.stdout)

Introducing mdview – a lightweight Markdown viewer

My favorite editor is vim, but it has downsides as well. Vim doesn’t have a the GUI needed to extend it to preview things like Markdown properly. Yeah, sure vim can highlight Markdown syntax, but that is not a replacement for real previewing. With that itch in mind, I searched for a solution but found none that satisfied me. For reStructuredText I’ve found a solution that worked well. It worded by starting a local web-server and does the previewing in the browser. Inspired by it, I started writing mdview.

mdview allows you to instantly preview in your favorite browser any Markdown file you’re editing. It will automatically refresh when the file is changed, hence it great for working with the editor and browser side-by-side for live preview.
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