Ensure ex-data is always inspectable (#587)

Fix blank screen caused by react unmounting when an exception occurs during `clerk/show!`. Also make parsed (but not evaluated) documents representable.

Fixes #586.

CHANGELOG.md

@@ -21,6 +21,8 @@ Changes can be:
   * `com.taoensso/nippy` to `3.4.0-beta1`
   * `io.github.nextjournal/markdown` to `0.5.146`
 
+* 🐜 Fix blank screen caused by react unmounting when an exception occurs during `clerk/show!`, fixes [#586](https://github.com/nextjournal/clerk/issues/586) @elken
+
 * 🐜 Make edn transmission resilient to symbols and keywords containing multiple slashes like `foo/bar/baz`. Those can be read by `read-string` but not in ClojureScript which is based on `tools.reader`.
 
 * 🐞 Fix caching behaviour of `clerk/image` and support overriding image-viewer by name

src/nextjournal/clerk/render.cljs

@@ -484,7 +484,7 @@
           [:div.font-bold "Unhandled " type])
         [:div.font-bold.mt-1 message]
         (when data
-          [:div.mt-1 [inspect data]])])
+          [:div.mt-1 [inspect (viewer/inspect-wrapped-values data)]])])
      via))
    [:div.py-6.overflow-x-auto
     [:table.w-full

src/nextjournal/clerk/viewer.cljc

@@ -610,6 +610,9 @@
 
 #_(present @nextjournal.clerk.webserver/!doc)
 
+(defn update-if [m k f] (if (k m) (update m k f) m))
+#_(update-if {:n "42"} :n #(Integer/parseInt %))
+
 (defn with-block-viewer [doc {:as cell :keys [type id]}]
   (case type
     :markdown (let [{:keys [content]} (:doc cell)
@@ -623,7 +626,7 @@
                                                    ::doc doc} doc))]))
                         (partition-by (comp #{:image} :type) content)))
 
-    :code (let [cell (update cell :result apply-viewer-unwrapping-var-from-def)
+    :code (let [cell (update-if cell :result apply-viewer-unwrapping-var-from-def)
                 {:keys [code? result? fold?]} (->display cell)
                 eval? (-> cell :result :nextjournal/value (get-safe :nextjournal/value) viewer-eval?)]
             (cond-> []
@@ -632,7 +635,7 @@
                       {:nextjournal/render-opts (assoc (select-keys cell [:loc])
                                                        :id (processed-block-id (str id "-code")))}
                       (dissoc cell :result)))
-              (or result? eval?)
+              (and (:result cell) (or result? eval?))
               (conj (cond-> (ensure-wrapped (-> cell (assoc ::doc doc) (set/rename-keys {:result ::result})))
                       (and eval? (not result?))
                       (assoc :nextjournal/viewer (assoc result-viewer :render-fn '(fn [_] [:<>])))))))))
@@ -867,7 +870,8 @@
   {:name `throwable-viewer
    :render-fn 'nextjournal.clerk.render/render-throwable
    :pred (fn [e] (instance? #?(:clj Throwable :cljs js/Error) e))
-   :transform-fn (comp mark-presented (update-val (comp demunge-ex-data datafy/datafy)))})
+   :transform-fn (comp mark-presented (update-val (comp demunge-ex-data
+                                                        datafy/datafy)))})
 
 (def image-viewer
   {#?@(:clj [:pred #(instance? BufferedImage %)
@@ -1137,13 +1141,6 @@
                (map (juxt #(list 'quote (symbol %)) #(->> % deref deref (list 'quote))))
                (extract-sync-atom-vars doc)))))
 
-(defn update-if [m k f]
-  (if (k m)
-    (update m k f)
-    m))
-
-#_(update-if {:n "42"} :n #(Integer/parseInt %))
-
 (declare html doc-url)
 
 (defn home? [{:keys [nav-path]}]

test/nextjournal/clerk/eval_test.clj

@@ -240,4 +240,3 @@
              (catch Exception _ nil))
         (clerk/show! (java.io.StringReader. code))
         (is (= result-first-run (get-result)))))))
-

test/nextjournal/clerk/parser_test.clj

@@ -3,7 +3,8 @@
             [matcher-combinators.matchers :as m]
             [matcher-combinators.test :refer [match?]]
             [nextjournal.clerk.analyzer-test :refer [analyze-string]]
-            [nextjournal.clerk.parser :as parser]))
+            [nextjournal.clerk.parser :as parser]
+            [nextjournal.clerk.view :as view]))
 
 (defmacro with-ns-binding [ns-sym & body]
   `(binding [*ns* (find-ns ~ns-sym)]
@@ -156,3 +157,13 @@ par two"))))
   (testing "unreadable forms"
     (is (= (parser/text-with-clerk-metadata-removed "^{:un :balanced :map} (do nothing)" clerk-ns-alias)
            "^{:un :balanced :map} (do nothing)"))))
+
+(deftest presenting-a-parsed-document
+  (testing "presenting a parsed document doesn't produce garbage"
+    (is (match? [{:nextjournal/viewer {:name 'nextjournal.clerk.viewer/code-block-viewer}}
+                 {:nextjournal/viewer {:name 'nextjournal.clerk.viewer/code-block-viewer}}
+                 {:nextjournal/viewer {:name 'nextjournal.clerk.viewer/code-block-viewer}}]
+                (-> (parser/parse-clojure-string {:doc? true} "(ns testing-presented-parsed) 123 :ahoi")
+                    view/doc->viewer
+                    :nextjournal/value
+                    :blocks)))))