Fix Images in slideshow viewer (#450)

Fixes serving blob objects in cases where the presented document doesn't contain a `:blocks` key. This happens with a custom notebook viewer as e.g. in the slideshow viewer. 

Co-authored-by: Martin Kavalar <[email protected]>

Author: zampino

notebooks/slideshow.clj

@@ -18,7 +18,6 @@
 (clerk/plotly {:data [{:z [[1 2 3] [3 2 1]] :type "surface"}]})
 
 ;; ---
-
 ;; ## 📈 Vega Lite
 ^{::clerk/visibility {:code :hide}}
 (clerk/vl {:width 650 :height 400 :data {:url "https://vega.github.io/vega-datasets/data/us-10m.json"
@@ -27,5 +26,10 @@
                                             :key "id" :fields ["rate"]}}]
            :projection {:type "albersUsa"} :mark "geoshape" :encoding {:color {:field "rate" :type "quantitative"}}})
 
+;; ---
+;; ## 🖼️ An Image
+^{::clerk/visibility {:code :hide}}
+(clerk/image "trees.png")
+
 ;; ---
 ;; # 👋🏻 Fin.

src/nextjournal/clerk/webserver.clj

@@ -75,10 +75,10 @@
 (defn blob->presented [presented-doc]
   ;; TODO: store on doc?
   (into {}
-        (comp (filter #(and (map? %) (contains? % :nextjournal/presented)))
+        (comp (filter #(and (map? %) (v/get-safe % :nextjournal/blob-id) (v/get-safe % :nextjournal/presented)))
               (map (juxt :nextjournal/blob-id :nextjournal/presented)))
         (tree-seq coll? seq
-                  (-> presented-doc v/->value :blocks))))
+                  (:nextjournal/value presented-doc))))
 
 #_(blob->presented (meta @!doc))