analyzing unused and undefined re-frame subscriptions via clj-kondo

analyze.clj

(ns analyze.core
  (:require [clj-kondo.core :as clj-kondo]
            [clojure.set :as set]))

;; checks re-frame's :<- syntax
;; to mark dependency subscriptions as used
(def analyze-reg-sub
  "(require '[clj-kondo.hooks-api :as api])
  (fn [{node :node}]
    (let [[_ kw & children] (:children node)
          reg-sub-kw (api/reg-keyword! kw 're-frame.core/reg-sub)
          reg-dep-kw! #(-> % :children first (api/reg-keyword! 're-frame.core/subscribe))
          sub-kws (map #(if (api/vector-node? %) (reg-dep-kw! %) %)
                       (butlast children))]
      {:node (api/list-node
               `(do ~reg-sub-kw ~@sub-kws ~(last children)))}))")

;; requires subscribtion name (keyword)
;; to be statically defined at the call site
;; i.e. `(subscribe [:my/sub])`
(def analyze-subscribe
  "(require '[clj-kondo.hooks-api :as api])
  (fn [{node :node}]
    (let [[_ query] (:children node)
          [kw & children] (:children query)]
      {:node (api/list-node
               `(do ~(api/reg-keyword! kw 're-frame.core/subscribe)
                    ~@children))}))")

(def out
  (clj-kondo/run!
    {:lint ["src"]
     :config {:output {:analysis {:keywords true}}
              :hooks {:__dangerously-allow-string-hooks__ true
                      :analyze-call {'re-frame.core/reg-sub analyze-reg-sub
                                     're-frame.core/subscribe analyze-subscribe}}}}))

(defn get-keywords-usages [var-name]
  (->> (:analysis out)
       :keywords
       (filter #(= var-name (:def %)))
       (map #(assoc % :kw (if (:ns %)
                            (keyword (str (:ns %)) (:name %))
                            (keyword (:name %)))))))

(defn find-unused-keywords [defs usages]
  (let [defs-set (into #{} (map :kw) defs)
        usages-set (into #{} (map :kw) usages)
        unused (set/difference defs-set usages-set)]
    (filter (comp unused :kw) defs)))

(defn find-usage-of-undefined-keywords [defs usages]
  (let [defs-set (into #{} (map :kw) defs)
        usages-set (into #{} (map :kw) usages)
        undefined (set/difference usages-set defs-set)]
    (filter (comp undefined :kw) defs)))

(defn fmt-message [warning-type {:keys [kw filename row]}]
  (-> (case warning-type
        :unused-subscription "Unused subscription")
      (str " " kw " at line " row  " in " filename)))

(let [subs [(get-keywords-usages 're-frame.core/reg-sub)
              (get-keywords-usages 're-frame.core/subscribe)]
      unused-subs (apply find-unused-keywords subs)
      undefined-subs (apply find-usage-of-undefined-keywords subs)]
  (doseq [sub unused-subs]
      (println (fmt-message :unused-subscription sub))))