You can also customize the printer e.g.

(defn my-assert [spec val]
  (binding [s/*explain-out* my-printer]
    (s/assert spec val)))

this looks better than what I asked for

so I get to take the assertion failure, as clojure data, rewrite it, then print it out

Yep, you can format it however you want

Also, if you happen to want an out of the box experience, you can use expound

It doesn’t actually help in this specific case (it prints out the entire value when it is missing keys), but you can provide a custom function to print out the value in this specific case

https://github.com/bhb/expound#configuring-the-printer

in that case, you’ll get the spec-name and some other data, which might be enough to detect this particular case.

Or you could even write your own printer which inspects the explain-data and does something custom for keys specs, but passes it along to expound otherwise.

when an assertion happens, I want it to pop up a new browser window, print the first level of the data, have + buttons next to parts that can be expand (and expands when I click on them), and highlights in a red DOM rectangle the key/value pair that is failing the spec

someone needs to build that 🙂

Would https://github.com/jpmonettas/inspectable#specs-fail-explain-why work?

this is amazing

why is https://github.com/jpmonettas/inspectable#specs-fail-explain-why not common knowledge ?

No idea, it seems like a great tool, maybe we need a collection of these helper libraries