meta-info.md

We want to reduce analysis cache size by deduping info stored in a def and also under its :meta key. Naive deduping can reduce cache size by 20-30%. Per @swannodette, https://clojurians.slack.com/archives/clojurescript/p1480348180020797, this would be a desireable cljs patch.

Open Questions

• Under what conditions should the :file key contain an absolute path, relative path, file extension, nothing at all?
• Why does :column differ between :file and :meta?
• How much of this data can we drop? when and how do cljs applications rely on this metadata?
• Why does teh :argslist differ between the def and its :meta key?

Output

Below, we read into a compiler state to see how the values in a def differ from those of its :meta key. We get-in'ing paths like:
[:cljs.analyzer/namespaces ~ns :defs ~sym] and [:cljs.analyzer/namespaces ~ns :defs ~sym :meta].

;; cljs.core/rand-int - core name, file is relative path

 :file       cljs/core.cljs
 :meta/:file cljs/core.cljs

 :column       1
 :meta/:column 7
 

;; cljs.core$macros/-> - core macro, file shows output-dir, meta/file is abs. path

 :file       out/cljs/core.cljc
 :meta/:file /Users/MattPro/Dropbox/Sites/planck/planck-cljs/out/cljs/core.cljc

 :column       4
 :meta/:column 19

 :arglists       ([&form &env x & forms])
 :meta/:arglists (quote ([x & forms]))
 

;; cljs.spec/conform - name, file shows output-dir, meta/file is abs. path

 :file       out/cljs/spec.cljs
 :meta/:file /Users/MattPro/Dropbox/Sites/planck/planck-cljs/out/cljs/spec.cljs

 :column       1
 :meta/:column 7
 

;; cljs.spec$macros/def - macro, meta/file has no extension

 :file       cljs/spec.cljc
 :meta/:file cljs.spec

 :column       1
 :meta/:column 11
 

;; maria.user/circle - file and meta/file are absolute paths

 :file       /Users/MattPro/Dropbox/Sites/maria/src/maria/user.cljs
 :meta/:file /Users/MattPro/Dropbox/Sites/maria/src/maria/user.cljs

 :column       1
 :meta/:column 7
 

;; maria.user$macros/user-macro - file is abs. path, meta/file has no extension

 :file       /Users/MattPro/Dropbox/Sites/maria/src/maria/user.clj
 :meta/:file maria.user

 :column       1
 :meta/:column 11

 :arglists       ([&form &env & body])
 :meta/:arglists (quote ([& body]))

This analysis cache was produced using cljs-live, which sources from a ClojureScript output-dir, falling back to Planck repl caches.

repl-code.cljs

;; the following code was run in a bootstrapped clojurescript repl
;; here: maria-d04a7.firebaseapp.com

(require '[cljs.spec :as s :include-macros true])
(require 'maria.eval)
(def cs maria.eval/c-state)
(require '[cljs.analyzer :as ana])

(defn get-def [ns sym]
  (-> @cs 
      (get-in [:cljs.analyzer/namespaces ns :defs sym])
      (dissoc :meta)))
(defn get-meta [ns sym]
  (-> @cs
      (get-in [:cljs.analyzer/namespaces ns :defs sym :meta])))

(defn show-str [s] (html [:div s]))

(defn compare-var-meta [n]
  (let [ns (symbol (namespace n))
        sym (symbol (name n))
        meta# (get-meta ns sym) 
        def# (get-def ns sym)]
    
    (show-str 
      (str "\n"(symbol ns sym) "\n"
       (apply str 
            (for [k (keys meta#)
                 :when (or (= k :file)
                           (not= (get meta# k)
                             (get def# k)))]
             (str "\n " k"       " (get def# k) "\n"
                  " :meta/" k" " (get meta# k) "\n") ))))))
  
  (map compare-var-meta ['cljs.spec/conform 
                         'cljs.spec$macros/def
                         'cljs.core/rand-int
                         'maria.user/circle
                         'maria.user$macros/user-macro])