I'm relatively new to Clojure and have been interested in writing something like this. I have a few questions/comments:

- What made you decide to write CacheBustHelper in Java? I believe something like:

  (defn bust-cache
    [input-stream]
    (with-open [rdr (clojure.java.io/reader input-stream)]
      (doseq [b (.read rdr)
              :when (not= -1 b)]
        nil)))

I'm not sure the performance difference between the two though.

- Does it work with any web backend framework? Could I use something like Luminus or Fulcro? Does the request just have to follow the Ring request format?

- Looks like lines 183 through 198 on core.clj could be when instead of if

- what about making update-if-present:

  (defn update-if-present
    [m & v]
      (reduce (fn [acc [k f]] 
                (if (contains? acc k) 
                  (update acc k f)
                  acc))
              m
              (partition 2 v)))

That would allow you to do the following:

  (update-if-present page-data :twitter-image cache-bust-one
                               :og-image cache-bust-one
                               :favicon cache-bust-one
                               :link-apple-icon cache-bust-one
                               :link-apple-startup-image cache-bust-one
                               :link-image-src cache-bust-one
                               :script cache-bust
                               :script-sync cache-bust
                               :js-module cache-bust
                               :stylesheet cache-bust
                               :stylesheet-async cache-bust
                               :manifest cache-bust-one)

Those are just some things I noticed on first glance.

-

My lib for Clojure, using it in a real project. Currently planning next iteration, probably will include prefetch links and streamline cache-busting. Most brutal critique is welcome as well as other forms of feedback.

Cheers!