Clojure: code highlights for this website

When I changed the styling of this website I removed code highlights as part of an exercise in minimalism. Anyway, I recently read this awesome article about writing a Clojure highlighter from scratch in 160 lines which inspired me to add some very basic highlights back to this site. This post is about implementing my own Clojure highlighter from scratch in 8 lines (and a fraction of the functionality).

I currently use monochrome highlights in my editor. I find it less distracting and it means I can use colour where I feel it matters (error, linter warnings etc). Thankfully this also greatly simplifies what this highlighter needs to support. All it needs to do make the symbol after def/defn/defmacro/ns etc bold.

Without further fanfare here is the highlighter:

(defn clojure-bold-defs [html]
  (str/replace html
               #"<code class=\"[Cc]lojure\">([\s\S]+?)</code>"
               (fn [[full-capture]]
                 (str/replace
                  full-capture
                  #"(&#40;def[a-z]* |ns )(\S+)"
                  "$1<strong>$2</strong>"))))

Lets break this code down. First we need to find the html code blocks that have a class "clojure":

(defn clojure-bold-defs [html]
  (str/replace html
               #"<code class=\"[Cc]lojure\">([\s\S]+?)</code>"
               ...))

Then we need to replace any code that starts with (def foo ... with (def <strong>foo</strong> ...:

(fn [[full-capture]]
                 (str/replace
                  full-capture
                  #"((def[a-z]* |ns )(\S+)"
                  "$1<strong>$2</strong>"))

We use ( the HTML coded character for ( because that's the format of our html input.

That's all there is to it. This very same code generates the minimalist code highlights on this website.

The full example can be found here.