Move sync state out of viewer eval to speed up recomputation (#722)

Author: mk

notebooks/large_sync.clj

@@ -0,0 +1,37 @@
+(ns large-atom-sync
+  (:require [nextjournal.clerk :as clerk]))
+
+;; # Clerk synced atoms and large data
+
+;; **1.** Define a Clerk synced atom called `!state`.
+
+(def el
+  {:hi :this
+   :is :a
+   :large :sync})
+
+^::clerk/sync
+(defonce !state
+  (atom (vec (repeat 20000 el))))
+
+;; **2.** Verify that `!state` is present on both sides.
+(clerk/eval-cljs '!state)
+
+;; **3.** Make a button to cram a lot of data into `!state` on the SCI side.
+
+^{::clerk/visibility {:code :hide :result :hide}}
+(def large-sync-button-viewer
+  {:render-fn '(fn [_]
+                 [:button.bg-sky-500.text-white.rounded-xl.px-2.py-1
+                  
+                  {:on-click (fn [_]
+                               (swap! large-atom-sync/!state conj {:rand-int (rand-int 42000)}))}
+                  "Click for large sync!"])})
+
+^{::clerk/viewer large-sync-button-viewer}
+{}
+
+(peek @!state)
+
+;; **4.** Click the button to see what happens 🙂
+#_(clerk/recompute!)

src/nextjournal/clerk/render.cljs

@@ -687,11 +687,15 @@
   (true? (some #(= % :nextjournal.clerk/remount) (tree-seq coll? seq doc-or-patch))))
 
 (defn re-eval-render-fns [doc]
+  ;; TODO: `intern-atoms!` is currently called twice in case of a
+  ;; remount patch-state! event
+  (intern-atoms! (-> doc :nextjournal/value :atom-var-name->state))
   (let [re-eval (fn [{:keys [form]}] (viewer/->render-fn form))]
     (w/postwalk (fn [x] (cond-> x (and (viewer/render-fn? x) (not (:eval x))) re-eval)) doc)))
 
 (defn eval-cljs-evals [doc]
   (reset! !render-errors [])
+  (intern-atoms! (-> doc :nextjournal/value :atom-var-name->state))
   (w/postwalk (fn [x]
                 (if (viewer/render-eval? x)
                   (try (deref (:f x))

src/nextjournal/clerk/viewer.cljc

@@ -1183,11 +1183,10 @@
         blocks))
 
 (defn atom-var-name->state [doc]
-  (->render-eval
-   (list 'nextjournal.clerk.render/intern-atoms!
-         (into {}
-               (map (juxt #(list 'quote (symbol %)) #(->> % deref deref (list 'quote))))
-               (extract-sync-atom-vars doc)))))
+  (into {}
+        (map (fn [sync-var]
+               [(symbol sync-var) @@sync-var]))
+        (extract-sync-atom-vars doc)))
 
 (defn home? [{:keys [nav-path]}]
   (contains? #{"src/nextjournal/home.clj" "'nextjournal.clerk.home"} nav-path))

test/nextjournal/clerk/viewer_test.clj

@@ -348,9 +348,7 @@
     (is (not-empty (-> (view/doc->viewer (eval/eval-string "(ns nextjournal.clerk.test.sync-vars (:require [nextjournal.clerk :as clerk]))
                                      ^::clerk/sync (def sync-me (atom {:a ['b 'c 3]}))"))
                        :nextjournal/value
-                       :atom-var-name->state
-                       :form
-                       second)))
+                       :atom-var-name->state)))
 
     (is (thrown-with-msg?
          clojure.lang.ExceptionInfo