Currently gets any top level forms which have metadata and wraps them with something which prints the locals, the form and the result of evaluation every time it's called. Issues include not coping with recur/throw where the tail of the function is no longer correct, and it doesn't show you for example the results of evaluating inside vectors or…

gistfile1.clj

(defmacro locals [] (zipmap (map #(list 'quote %) (keys &env)) (keys &env)))

(defn remove-autogenerated-locals
  "Remove any locals generated by macros (heuristic - named something
  with underscores in it). When we're doing something other than
  println with the data, these could be left in but it's a bit noisy
  at the moment"
  [coll]
  (into {} (remove (fn [[k v]] (re-find  #"[_]" (name k))) coll)))

(defn eval-printing-meta [location form subform]
  (let [local-things `(locals)]
    `(let [result# ~subform]
       (binding [*print-length* 10]
         (clojure.pprint/pprint {:result result# :location ~location :form (quote ~form) :locals (remove-autogenerated-locals ~local-things)}))
       result#)))

(defn wrap-things-with-meta [form]
  (if (meta form)
    (eval-printing-meta (meta form) form (map wrap-things-with-meta form))
    form))

(defmacro lexically-trace [body]
  (list 'do
        (list 'println "Entering lexically-trace at " (meta &form))
        (wrap-things-with-meta body)))

;;; Currently doesn't work due to the recur no longer being in tail position:
(comment 
 (defn test-recursion [x y]
   (lexically-trace (if (= y 0) [x y] (recur (inc x) (dec y))))))

(defn test-nested [a]
  (lexically-trace
   (+ a (- (let [x 10] (/ 4 x a)) (let [a 2] (* a 7))))))

(defn test-ranges [max]
  (lexically-trace (+ max (first (range)))))