DXML-25 emit empty elements

Author: bendlas

src/main/clojure/clojure/data/xml/event.clj

@@ -31,6 +31,7 @@
 
 ; Represents a parse event.
 (defrecord StartElementEvent [tag attrs nss location-info])
+(defrecord EmptyElementEvent [tag attrs nss location-info])
 (defrecord CharsEvent [str])
 (defrecord CDataEvent [str])
 (defrecord CommentEvent [str])
@@ -45,19 +46,22 @@
 
 (let [second-arg #(do %2)
       elem-event-generation
-      {:gen-event (fn elem-gen-event [{:keys [tag attrs] :as element}]
+      {:gen-event (fn elem-gen-event [{:keys [tag attrs content] :as element}]
                     (separate-xmlns
-                     attrs #(->StartElementEvent
+                     attrs #((if (seq content)
+                               ->StartElementEvent ->EmptyElementEvent)
                              tag %1 (merge-nss (element-nss* element) %2) nil)))
        :next-events (fn elem-next-events [{:keys [tag content]} next-items]
-                      (list* content end-element-event next-items))}
+                      (if (seq content)
+                        (list* content end-element-event next-items)
+                        next-items))}
       string-event-generation {:gen-event (comp ->CharsEvent #'xml-str)
                                :next-events second-arg}
       qname-event-generation {:gen-event ->QNameEvent
                               :next-events second-arg}]
   (extend-protocol-fns
    EventGeneration
-   (StartElementEvent EndElementEvent CharsEvent CDataEvent CommentEvent)
+   (StartElementEvent EmptyElementEvent EndElementEvent CharsEvent CDataEvent CommentEvent)
    {:gen-event identity
     :next-events second-arg}
    (String Boolean Number (Class/forName "[B") Date URI URL nil)
@@ -89,7 +93,8 @@
 ;; Node Generation for events
 
 (defn event-element [event contents]
-  (when (instance? StartElementEvent event)
+  (when (or (instance? StartElementEvent event)
+            (instance? EmptyElementEvent event))
     (element* (:tag event) (:attrs event) contents
               (if-let [loc (:location-info event)]
                 {:clojure.data.xml/location-info loc

src/main/clojure/clojure/data/xml/jvm/emit.clj

@@ -23,7 +23,7 @@
            (javax.xml.stream XMLStreamWriter XMLOutputFactory)
            (javax.xml.transform OutputKeys Transformer
                                 TransformerFactory)
-           (clojure.data.xml.event StartElementEvent EndElementEvent CharsEvent CDataEvent CommentEvent QNameEvent)
+           (clojure.data.xml.event StartElementEvent EmptyElementEvent EndElementEvent CharsEvent CDataEvent CommentEvent QNameEvent)
            (clojure.lang BigInt)
            (java.net URI URL)
            (java.util Date)
@@ -112,17 +112,24 @@
               tpu)]
     (pu/persistent! tpu)))
 
-(defn- emit-start-tag [{:keys [attrs nss tag]} ^XMLStreamWriter writer prefix-uri-stack]
+(defn- emit-start-tag [{:keys [attrs nss tag]} ^XMLStreamWriter writer prefix-uri-stack empty]
   (let [uri   (qname-uri tag)
         local (qname-local tag)
         parent-pu (first prefix-uri-stack)
         pu (compute-pu parent-pu nss (map qname-uri (keys attrs)) uri local)]
-    (if (str/blank? uri)
-      (.writeStartElement writer local)
-      (.writeStartElement writer (pu/get-prefix pu uri) local uri))
-    (emit-ns-attrs writer parent-pu pu)
-    (emit-attrs writer pu attrs)
-    (cons pu prefix-uri-stack)))
+    (if empty
+      (do (if (str/blank? uri)
+            (.writeEmptyElement writer local)
+            (.writeEmptyElement writer (pu/get-prefix pu uri) local uri))
+          (emit-ns-attrs writer parent-pu pu)
+          (emit-attrs writer pu attrs)
+          prefix-uri-stack)
+      (do (if (str/blank? uri)
+            (.writeStartElement writer local)
+            (.writeStartElement writer (pu/get-prefix pu uri) local uri))
+          (emit-ns-attrs writer parent-pu pu)
+          (emit-attrs writer pu attrs)
+          (cons pu prefix-uri-stack)))))
 
 (defn- emit-cdata [^String cdata-str ^XMLStreamWriter writer]
   (when-not (str/blank? cdata-str)
@@ -135,7 +142,9 @@
 
 (extend-protocol EventEmit
   StartElementEvent
-  (emit-event [ev writer pu-stack] (emit-start-tag ev writer pu-stack))
+  (emit-event [ev writer pu-stack] (emit-start-tag ev writer pu-stack false))
+  EmptyElementEvent
+  (emit-event [ev writer pu-stack] (emit-start-tag ev writer pu-stack true))
   EndElementEvent
   (emit-event [ev writer pu-stack]
     (assert (next pu-stack) "balanced tags")

src/main/clojure/clojure/data/xml/jvm/parse.clj

@@ -9,15 +9,16 @@
 (ns clojure.data.xml.jvm.parse
   (:require [clojure.string :as str]
             [clojure.data.xml.event :refer
-             [->StartElementEvent ->EndElementEvent
+             [->StartElementEvent ->EmptyElementEvent ->EndElementEvent
               ->CharsEvent ->CDataEvent ->CommentEvent]]
             [clojure.data.xml.impl :refer
              [static-case]]
             [clojure.data.xml.name :refer
              [qname]])
   (:import
    (javax.xml.stream
-    XMLInputFactory XMLStreamReader XMLStreamConstants)))
+    XMLInputFactory XMLStreamReader XMLStreamConstants)
+   (clojure.data.xml.event EndElementEvent)))
 
 (def ^{:private true} input-factory-props
   {:allocator XMLInputFactory/ALLOCATOR
@@ -76,14 +77,16 @@
          (.next sreader)
          XMLStreamConstants/START_ELEMENT
          (if (include-node? :element)
-           (let [ns-env (nss-hash sreader (or (first ns-envs) {}))]
-             (cons (->StartElementEvent (qname (.getNamespaceURI sreader)
-                                               (.getLocalName sreader)
-                                               (.getPrefix sreader))
-                                        (attr-hash sreader)
-                                        ns-env
-                                        location)
-                   (pull-seq sreader opts (cons ns-env ns-envs))))
+           (let [ns-env (nss-hash sreader (or (first ns-envs) {}))
+                 tag (qname (.getNamespaceURI sreader)
+                            (.getLocalName sreader)
+                            (.getPrefix sreader))
+                 attrs (attr-hash sreader)
+                 next-events (pull-seq sreader opts (cons ns-env ns-envs))]
+             ;; Can't emit EmptyElementEvent here, since
+             ;; for seq-tree node and exit? are mutually exclusive
+             (cons (->StartElementEvent tag attrs ns-env location)
+                   next-events))
            (recur))
          XMLStreamConstants/END_ELEMENT
          (if (include-node? :element)

src/test/clojure/clojure/data/xml/test_emit.clj

@@ -218,3 +218,7 @@
     (is (= {:xmlns "NS"}
            (nss-meta (parse-str "<foo xmlns=\"NS\"/>"))
            (nss-meta (parse-str (emit-str (parse-str "<foo xmlns=\"NS\"/>"))))))))
+
+(deftest test-empty-elements
+  (is (= (emit-str {:tag :a :content []}) "<?xml version=\"1.0\" encoding=\"UTF-8\"?><a/>"))
+  (is (= (emit-str {:tag :a :content [""]}) "<?xml version=\"1.0\" encoding=\"UTF-8\"?><a></a>")))