Setting up instrumentation on clojure.core with Expound

core.clj

;; Set up instrumentation somewhere in your project
;; (only need to do this once)
(require '[clojure.core.specs.alpha])
(require '[clojure.spec.alpha :as s])
(require '[clojure.spec.test.alpha :as stest])
(require '[expound.alpha :as expound])
(set! s/*explain-out* expound/printer)
(stest/instrument)

;;; later on ...

(ns "docstring " foo.bar)

;; CompilerException clojure.lang.ExceptionInfo: Call to clojure.core/ns did not conform to spec:
;; -- Spec failed --------------------

;; ("docstring " ...)
;; ^^^^^^^^^^^^

;; should satisfy

;; simple-symbol?

;; -- Relevant specs -------

;; :clojure.core.specs.alpha/ns-form:
;; (clojure.spec.alpha/cat
;;  :name
;;  clojure.core/simple-symbol?
;;  :docstring
;;  (clojure.spec.alpha/? clojure.core/string?)
;;  :attr-map
;;  (clojure.spec.alpha/? clojure.core/map?)
;;  :clauses
;;  :clojure.core.specs.alpha/ns-clauses)

;; -------------------------
;; Detected 1 error