Add dynamic js/import for JavaScript Modules (#304)

* Extend js global namespace with dynamic `js/import`
* Add convenience react hook wrappers

notebooks/js_import.clj

@@ -0,0 +1,58 @@
+;; # 📦 Dynamic JS Imports
+(ns js-import
+  {:nextjournal.clerk/visibility {:code :hide :result :hide}}
+  (:require [nextjournal.clerk :as clerk]
+            [nextjournal.clerk.viewer :as clerk.viewer]
+            [clojure.data.csv :as csv]))
+
+;; This example uses [Observable Plots](https://observablehq.com/plot) with data from https://allisonhorst.github.io/palmerpenguins/
+
+(defn parse-float [^String s] (Float/parseFloat s))
+
+^{::clerk/visibility {:code :show}}
+(def observable-plot-viewer
+  {:transform-fn clerk/mark-presented
+   :render-fn
+   '(fn [data _]
+      [nextjournal.clerk.render/with-dynamic-import
+       {:module "https://cdn.skypack.dev/@observablehq/[email protected]"}
+       (fn [Plot]
+         [:div {:ref (fn [el]
+                       (when el
+                         (let [dot-plot (.. Plot
+                                            (dot (clj->js data)
+                                                 (j/obj :x "flipper_length_mm"
+                                                        :y "body_mass_g"
+                                                        :fill "species"))
+                                            (plot (j/obj :grid true)))]
+                           (doto el
+                             (.append (.legend dot-plot "color"))
+                             (.append dot-plot)))))}])])})
+
+^{::clerk/visibility {:code :show :result :show}
+  ::clerk/viewer observable-plot-viewer}
+(def palmer-penguins
+  (-> (slurp "https://nextjournal.com/data/Qmf6FJyJxBQnB6TUZ3J9pdzHSs8UoewoY6WfdZHu1XxkD8?filename=penguins.csv&content-type=text/csv")
+      (csv/read-csv)
+      clerk.viewer/use-headers
+      clerk.viewer/normalize-table-data
+      (as-> data
+        (let [{:keys [head rows]} data]
+          (map (fn [row] (zipmap head (reduce #(update %1 %2 parse-float) row [1 2 3 4])))
+               rows)))))
+
+;; or use `js/import` directly:
+^{::clerk/visibility {:result :show :code :show} ::clerk/no-cache true ::clerk/width :wide}
+(nextjournal.clerk/with-viewer
+  '(fn [_]
+     (let [cc (nextjournal.clerk.render.hooks/use-promise
+               (js/import "https://cdn.skypack.dev/canvas-confetti"))
+           ref (nextjournal.clerk.render.hooks/use-ref)]
+       (when cc
+         [:div
+          [:button.bg-teal-500.hover:bg-teal-700.text-white.font-bold.py-2.px-4.rounded.rounded-full.font-sans
+           {:on-click #((.create cc @ref)
+                        (j/lit {:spread 80 :angle 45 :startVelocity 20 :origin {:x 0.25 :y 0.5}}))} "Peng 🎉!"]
+          [:canvas
+           {:ref ref
+            :style {:width "100%" :height "500px"}}]]))) nil)

src/nextjournal/clerk/builder.clj

@@ -26,6 +26,7 @@
          "eval_cljs"
          "example"
          "hiding_clerk_metadata"
+         "js_import"
          "multiviewer"
          "pagination"
          "paren_soup"

src/nextjournal/clerk/render.cljs

@@ -718,6 +718,12 @@
     (f package)
     loading-view))
 
+(defn with-dynamic-import [{:keys [module loading-view]
+                            :or {loading-view default-loading-view}} f]
+  (if-let [package (hooks/use-dynamic-import module)]
+    (f package)
+    loading-view))
+
 (defn render-vega-lite [value]
   (let [handle-error (hooks/use-error-handler)
         vega-embed (hooks/use-d3-require "[email protected]")

src/nextjournal/clerk/render/hooks.cljs

@@ -2,6 +2,7 @@
   (:require ["d3-require" :as d3-require]
             ["react" :as react]
             [reagent.ratom]
+            [shadow.esm :as esm]
             ["use-sync-external-store/shim" :refer [useSyncExternalStore]]))
 
 ;; a type for wrapping react/useState to support reset! and swap!
@@ -152,3 +153,7 @@
                                    list))
                          #js[(str package)])]
     (use-promise p)))
+
+(defn ^js use-dynamic-import [mod]
+  (let [p (use-memo #(esm/dynamic-import mod) [mod])]
+    (use-promise p)))

src/nextjournal/clerk/sci_env.cljs

@@ -24,7 +24,8 @@
             [sci.configs.applied-science.js-interop :as sci.configs.js-interop]
             [sci.configs.reagent.reagent :as sci.configs.reagent]
             [sci.core :as sci]
-            [sci.ctx-store]))
+            [sci.ctx-store]
+            [shadow.esm]))
 
 (defn ->viewer-fn-with-error [form]
   (try (viewer/->viewer-fn form)
@@ -120,7 +121,7 @@
   {:async? true
    :load-fn load-fn
    :disable-arity-checks true
-   :classes {'js goog/global
+   :classes {'js (j/assoc! goog/global "import" shadow.esm/dynamic-import)
              'framer-motion framer-motion
              :allow :all}
    :aliases {'j 'applied-science.js-interop