fix round-trip prefix assignments

this cleans up usage of metadata to always store strings into
nss-attrs

this way, our emitter can restore prefixes and default xmlns, exactly
as they appeared in a source

Author: bendlas

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

@@ -82,14 +82,15 @@
 
 (defn- compute-pu [pu ns-attrs attr-uris tag-uri tag-local]
   (let [tpu (pu/transient pu)
+        ;; add xmlns, if exists
+        tpu (if-let [uri (get ns-attrs "xmlns")]
+              (pu/assoc! tpu "" uri)
+              tpu)
         ;; add namespaces from current environment
         tpu (reduce-kv (fn [tpu ns-attr uri]
+                         (assert (string? ns-attr) (pr-str ns-attr))
                          (pu/assoc! tpu
-                                    (if (str/blank? (qname-uri ns-attr))
-                                      (do (assert (= "xmlns" (qname-local ns-attr))
-                                                  "non-prefixed attribute, that's not xmlns= is not a namespace attr")
-                                          "")
-                                      (compute-prefix tpu uri (qname-local ns-attr)))
+                                    (compute-prefix tpu uri ns-attr)
                                     uri))
                        tpu ns-attrs)
         ;; add implicit namespaces used by tag, attrs

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

@@ -51,7 +51,7 @@
    (reduce (fn [tr ^long i]
              (let [ns-pf (.getNamespacePrefix sreader i)]
                (assoc! tr (if (str/blank? ns-pf)
-                            :xmlns ns-pf)
+                            "xmlns" ns-pf)
                        (.getNamespaceURI ^XMLStreamReader sreader i))))
            (transient parent-hash)
            (range (.getNamespaceCount sreader)))))

src/main/clojure/clojure/data/xml/name.cljc

@@ -141,11 +141,10 @@
 (defn xmlns-attr?
   "Is this qname an xmlns declaration?"
   [qn]
-  (let [uri (qname-uri qn)
-        local (qname-local qn)]
+  (let [uri (qname-uri qn)]
     (or (= xmlns-uri uri)
         (and (str/blank? uri)
-             (= "xmlns" local)))))
+             (= "xmlns" (qname-local qn))))))
 
 (defn separate-xmlns
   "Call cont with two args: attributes and xmlns attributes"
@@ -157,7 +156,7 @@
       (let [val (get attrs qn)]
         (if (xmlns-attr? qn)
           (recur attrs*
-                 (assoc! xmlns* qn val)
+                 (assoc! xmlns* (qname-local qn) val)
                  (next attrs'))
           (recur (assoc! attrs* qn val)
                  xmlns*

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

@@ -221,10 +221,17 @@
 
 (deftest test-default-xmlns
   (let [nss-meta (comp :clojure.data.xml/nss meta)]
-    (is (= {:xmlns "NS"}
+    (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>")))
+
+(deftest test-roundtrip
+  (is (= (emit-str (with-meta (parse-str "<foo:element xmlns:foo=\"FOO:\"/>")
+                     nil))
+         "<?xml version=\"1.0\" encoding=\"UTF-8\"?><a:element xmlns:a=\"FOO:\"/>"))
+  (is (= (emit-str (parse-str "<foo:element xmlns:foo=\"FOO:\"/>"))
+         "<?xml version=\"1.0\" encoding=\"UTF-8\"?><foo:element xmlns:foo=\"FOO:\"/>")))