Fix html with odd length lists

[zampino]

Fixes #395.

The issue is due to some weird behaviour of cljs.core/reduce against vectors containing lists with an odd number of items.

clerk/src/nextjournal/clerk/viewer.cljc

Lines 1389 to 1393 in d387037

	(defn collect-expandable-paths [state {:nextjournal/keys [value] :keys [path]}]
	(let [state' (assoc-in state [:expanded-at path] false)]
	(if (vector? value)
	(reduce collect-expandable-paths state' value)
	state')))

(viewer/collect-expandable-paths 
 {:expanded-at {}}
 {:path [],
  :nextjournal/value [:h1 "Ahoi" (list [:div "one"] [:div "two"] [:div "three"])],
  :nextjournal/viewer {:name :html, :render-fn identity, :hash "5dqwbRQVFnHkdooT8QV8nfPHBGVWtj"}})

Causing:

Uncaught Error: :div is not ISeqable
    at Object.cljs$core$seq [as seq] (core.cljs:1253:20)
    at Object.cljs$core$ITransientCollection$_conj_BANG_$arity$2 (core.cljs:7198:20)
    at cljs$core$_conj_BANG_ (core.cljs:803:17)
    at core.cljs:5686:36
    at core.cljs:5686:35
    at Object.cljs$core$IReduce$_reduce$arity$3 (core.cljs:5690:24)
    at Function.cljs$core$IFn$_invoke$arity$3 (core.cljs:2570:17)
    at Function.cljs$core$IFn$_invoke$arity$2 (core.cljs:5266:36)
    at Function.createAsIfByAssocComplexPath (core.cljs:7134:21)
    at Function.createAsIfByAssoc 

The error is actually visible in browser console and it's not reproducible on the JVM.

[zampino]

As an alternative, we might just check that all (or just the first of) items in value are wrapped ones.

[zampino]

Narrowing down the above issue, it seems there's a discrepancy between clj/s in destructuring sequences.

The original issue is due to the following (reproduces in a cljs repl):

clj -M:cljs -m cljs.main -r
ClojureScript 1.11.60

cljs.user=> (let [{:keys [key]} (list [:key1 "one"] [:key2 "two"] [:key3 "three"])] key)
Execution error (Error) at (<cljs repl>:1).
:key3 is not ISeqable

cljs.user=> (js/console.log *e)

which produces the same stacktrace as the one above:

Error: :key3 is not ISeqable
    at Object.cljs$core$seq [as seq] (core.cljs:1253:20)
    at Object.cljs$core$ITransientCollection$_conj_BANG_$arity$2 (core.cljs:7198:20)
    at cljs$core$_conj_BANG_ (core.cljs:803:17)
    at core.cljs:5686:36
    at core.cljs:5686:35
    at Object.cljs$core$IReduce$_reduce$arity$3 (core.cljs:5690:24)
    at Function.cljs$core$IFn$_invoke$arity$3 (core.cljs:2570:17)
    at Function.cljs$core$IFn$_invoke$arity$2 (core.cljs:5266:36)
    at Function.createAsIfByAssocComplexPath (core.cljs:7134:21)
    at Function.createAsIfByAssoc (core.cljs:7126:40)

The caller of createAsIfByAssoc (not listed in the stack) should be seq-to-map-for-destructuring.

The same code just doesn't blow up in clojure:

clj -r
WARNING: Implicit use of clojure.main with options is deprecated, use -M
Clojure 1.11.1
user=> (let [{:keys [key]} (list [:key1 "one"] [:key2 "two"] [:key3 "three"])] key)
nil
user=>