Fix server side rendering (#730)

Fixes #706.

.github/workflows/main.yml

@@ -269,7 +269,8 @@ jobs:
       - name: Run Playwright tests against static assets
         run: |
           bb test:static-app :sha ${{ github.sha }} :skip-install true
-          bb test:static-app :skip-install true :url https://snapshots.nextjournal.com/clerk/book/${{ github.sha }}/book/index.html :index false :selector "span:has-text(\"Book of Clerk\")"
+          bb test:static-app :skip-install true :url https://snapshots.nextjournal.com/clerk/book/${{ github.sha }}/book/index.html :index false :selector "h1:has-text(\"Book of Clerk\")"
+          bb test:static-app :skip-install true :url https://snapshots.nextjournal.com/clerk-ssr/build/${{ github.sha }}/index.html :index false :selector "h1:has-text(\"Rule 30\")"
 
   deploy:
     needs: [build-and-upload-viewer-resources, test]

src/nextjournal/clerk/builder.clj

@@ -163,18 +163,36 @@
            :path->doc path->doc
            :paths (vec (keys path->doc)))))
 
+(defn- node-ssr!
+  [{:keys [viewer-js state]
+    :or {viewer-js
+         ;; for local REPL testing
+         "./public/js/viewer.js"}}]
+  (sh {:in (str "import '" viewer-js "';"
+                "globalThis.CLERK_SSR = true;"
+                "console.log(nextjournal.clerk.sci_env.ssr(" (pr-str (pr-str state)) "))")}
+      "node"
+      "--abort-on-uncaught-exception"
+      "--experimental-network-imports"
+      "--input-type=module"
+      "--trace-warnings"))
+
+(comment
+  (declare so) ;; captured in REPL in ssr! function
+  (node-ssr! {:state so})
+  )
+
 (defn ssr!
   "Shells out to node to generate server-side-rendered html."
   [{:as static-app-opts :keys [report-fn resource->url]}]
   (report-fn {:stage :ssr})
-  (let [{duration :time-ms :keys [result]}
-        (eval/time-ms (sh {:in (str "import '" (resource->url "/js/viewer.js") "';"
-                                    "console.log(nextjournal.clerk.sci_env.ssr(" (pr-str (pr-str static-app-opts)) "))")}
-                          "node"
-                          "--abort-on-uncaught-exception"
-                          "--experimental-network-imports"
-                          "--input-type=module"
-                          "--trace-warnings"))
+  (let [doc (get (:path->doc static-app-opts) (:current-path static-app-opts))
+        static-app-opts (-> (assoc static-app-opts :doc doc)
+                            (dissoc :path->doc)
+                            (assoc :render-router :serve))
+        {duration :time-ms :keys [result]}
+        (eval/time-ms (node-ssr! {:viewer-js (resource->url "/js/viewer.js")
+                                  :state static-app-opts}))
         {:keys [out err exit]} result]
     (if (= 0 exit)
       (do
@@ -203,9 +221,9 @@
           (spit (fs/file out-path (str (or (not-empty path) "index") ".edn"))
                 (viewer/->edn doc))
           (spit out-html (view/->html (-> static-app-opts
-                                          (dissoc :path->doc)
                                           (assoc :current-path path)
                                           (cond-> ssr? ssr!)
+                                          (dissoc :path->doc)
                                           cleanup))))))
     (when browse?
       (browse/browse-url (if-let [server-url (and (= out-path "public/build") (webserver/server-url))]

src/nextjournal/clerk/render.cljs

@@ -847,7 +847,8 @@
                                                   :status (.-status r)
                                                   :headers (.-headers r)})))))
       (then read-response+show-progress)
-      (then (fn [edn] (set-state! {:doc (read-string edn)}) {:ok true}))
+      (then (fn [edn]
+              (set-state! {:doc (read-string edn)}) {:ok true}))
       (catch (fn [e] (js/console.error "Fetch failed" e)
                (set-state! {:doc {:nextjournal/viewer {:render-fn (constantly [:<>])} ;; FIXME: make :error top level on state
                                   :nextjournal/value {:error (viewer/present e)}}})

src/nextjournal/clerk/render/hooks.cljs

@@ -75,7 +75,9 @@
 (defn use-ref
   "React hook: useRef. Can also be used like an atom."
   ([] (use-ref nil))
-  ([init] (specify-atom! (react/useRef init))))
+  ([init] (if (unchecked-get js/globalThis "CLERK_SSR")
+            (atom init)
+            (specify-atom! (react/useRef init)))))
 
 (defn ^:private eval-fn
   "Invoke (f x) if f is a function, otherwise return f"

src/nextjournal/clerk/sci_env.cljs

@@ -15,6 +15,7 @@
             [applied-science.js-interop :as j]
             [cljs.math]
             [cljs.reader]
+            [cljs.repl]
             [clojure.string :as str]
             [edamame.core :as edamame]
             [goog.object]

ui_tests/playwright_tests.cljs

@@ -52,16 +52,20 @@
    (p/do (goto page url)
          (.waitForLoadState page "networkidle")
          (p/let [selector (or (:selector @!opts) "div")
-                 loc (.locator page selector)
-                 loc (.first loc #js {:timeout 10000})]
-           (is (.isVisible loc #js {:timeout 10000})))))
+                 _ (prn :selector selector)
+                 loc (.locator page selector #js {:timeout 10000})
+                 loc (.first loc #js {:timeout 10000})
+                 _ (.waitFor loc #js {:state "visible"})
+                 visible? (.isVisible loc)]
+           (is visible?))))
   ([page url link]
    (p/let [txt (.innerText link)]
      (println "Visiting" (str url "#/" txt))
      (p/do (.click link)
            (p/let [loc (.locator page "div")
                    loc (.first loc #js {:timeout 10000})
-                   visible? (.isVisible loc #js {:timeout 10000})]
+                   _ (.waitFor loc #js {:state "visible"})
+                   visible? (.isVisible loc)]
              (is visible?))))))
 
 (deftest index-page-test