fix cljs multipart handling

Author: milt

src/main/com/yetanalytics/lrs/pedestal/http/multipart_mixed.cljc

@@ -49,40 +49,53 @@
     (throw (ex-info message
                     {:type type-k}))))
 
+(defn- boundary-pat-mid-simple
+  [boundary]
+  (format "\\r\\n--%s\\r\\n" boundary))
+
 #?(:cljs
    (defn split-multiparts
-     "Splits multipart body parts, ensuring start + end and at least 2 parts"
+     "Splits multipart body parts, ensuring start + end and at least 1 part"
      [boundary body]
      (let [open-re-pos (u/re-pos
                         (re-pattern
                          (boundary-pat-open boundary))
                         body)
+           ;; Use the same mid pattern as JVM, but without negative lookbehind
            mid-re-pos (u/re-pos
                        (re-pattern
-                        (boundary-pat-mid boundary))
+                        (boundary-pat-mid-simple boundary))
                        body)
            close-re-pos (u/re-pos
                          (re-pattern
                           (boundary-pat-close boundary))
                          body)
+
+           ;; Filter out any mid matches that are actually part of the opening
+           actual-mid-pos
+           (filter (fn [[idx _]]
+                     (let [open-end (when-let [[open-idx open-match] (first open-re-pos)]
+                                      (+ open-idx (count open-match)))]
+                       (or (nil? open-end) (>= idx open-end))))
+                   mid-re-pos)
+
            all-pos (concat open-re-pos
-                           mid-re-pos
+                           actual-mid-pos
                            close-re-pos)]
+
        (assert-valid (= 1 (count open-re-pos))
                      "Only one opening boundary can be present"
                      ::invalid-one-opening-boundary)
-       (assert-valid (<= 1 (count mid-re-pos))
-                     "At least one mid boundary must be present"
-                     ::invalid-at-least-one-mid-boundary)
+       (assert-valid (>= (count actual-mid-pos) 0)
+                     "Mid boundaries must be valid"
+                     ::invalid-mid-boundaries)
        (assert-valid (= 1 (count close-re-pos))
                      "Only one closing boundary can be present"
                      ::invalid-one-closing-boundary)
-       (for [[[idx-a
-               bound-a]
-              [idx-b]] (partition 2 1 all-pos)]
+
+       (for [[[idx-a bound-a] [idx-b]] (partition 2 1 all-pos)]
          (subs body
-               (+ idx-a
-                  (count bound-a))
+               (+ idx-a (count bound-a))
                idx-b)))))
 
 (defn parse-part [^String part boundary]
@@ -133,6 +146,7 @@
                   (split-multiparts boundary in))))
     (catch #?(:clj Exception
               :cljs js/Error) ex
+      #?(:cljs (.log js/console "error" ex))
       (throw (ex-info "Invalid Multipart Body"
                       {:type ::invalid-multipart-body}
                       ex)))))