Implement #xml/element reader tag

Unfortunately, this necessitates removal of hash caching, because
deftypes with mutable fields cannot be compiled: CLJ-2029

Author: bendlas

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

@@ -17,14 +17,6 @@
                    (java.io Serializable Writer)
                    (java.util Map))))
 
-#?
-(:clj
- ;; recreate cljs' caching-hash macro
- (defmacro caching-hash [this hash-fn hash-field]
-   `(do (when-not ~hash-field
-          (set! ~hash-field (~hash-fn ~this)))
-        ~hash-field)))
-
 ;; Parsed data format
 ;; Represents a node of an XML tree
 
@@ -36,9 +28,9 @@
 ;; also, elements don't have an extmap and degrade to hash-maps also
 ;; when assoc'ing unknown keys
 
-(deftype Element [tag attrs content meta
-                  #?(:clj ^:volatile-mutable hash
-                     :cljs ^:mutable hash)]
+;; FIXME hash caching cannot be used: http://dev.clojure.org/jira/browse/CLJ-2092
+
+(deftype Element [tag attrs content meta]
 
   ;; serializing/cloning, hashing, equality, iteration
 
@@ -47,14 +39,14 @@
    [Serializable
     MapEquivalence
     IHashEq
-    (hasheq [this] (caching-hash this APersistentMap/mapHasheq hash))
+    (hasheq [this] (APersistentMap/mapHasheq this))
     Iterable
     (iterator [this] (RecordIterator. this [:tag :attrs :content] (RT/iter nil)))]
    :cljs
    [ICloneable
-    (-clone [_] (Element. tag attrs content meta hash))
+    (-clone [_] (Element. tag attrs content meta))
     IHash
-    (-hash [this] (caching-hash this hash-unordered-coll hash))
+    (-hash [this] (hash-unordered-coll this))
     IEquiv
     (-equiv [this other] (or (identical? this other)
                              ^boolean (js/cljs.core.equiv_map this other)))
@@ -71,7 +63,7 @@
                            (concat [">"] content ["</" qname ">"])
                            ["/>"])))))
   #?@(:clj
-      [(hashCode [this] (caching-hash this APersistentMap/mapHash hash))
+      [(hashCode [this] (APersistentMap/mapHash this))
        (equals [this other] (APersistentMap/mapEquals this other))
        IPersistentMap
        (equiv [this other] (APersistentMap/mapEquals this other))])
@@ -98,9 +90,9 @@
   #?(:cljs IAssociative)
   (#?(:clj assoc :cljs -assoc) [this k v]
     (case k
-      :tag (Element. v attrs content meta nil)
-      :attrs (Element. tag v content meta nil)
-      :content (Element. tag attrs v meta nil)
+      :tag (Element. v attrs content meta)
+      :attrs (Element. tag v content meta)
+      :content (Element. tag attrs v meta)
       (with-meta {:tag tag :attrs attrs :content content k v} meta)))
   #?(:cljs IMap)
   (#?(:clj without :cljs -dissoc) [this k]
@@ -136,7 +128,7 @@
   (#?(:clj meta :cljs -meta) [this] meta)
   #?(:cljs IWithMeta)
   (#?(:clj withMeta :cljs -with-meta) [this next-meta]
-    (Element. tag attrs content next-meta hash))
+    (Element. tag attrs content next-meta))
 
   ;; cljs printing is protocol-based
 
@@ -179,18 +171,18 @@
 (defn element*
   "Create an xml element from a content collection and optional metadata"
   ([tag attrs content meta]
-   (Element. tag (or attrs {}) (remove nil? content) meta nil))
+   (Element. tag (or attrs {}) (remove nil? content) meta))
   ([tag attrs content]
-   (Element. tag (or attrs {}) (remove nil? content) nil nil)))
+   (Element. tag (or attrs {}) (remove nil? content) nil)))
 
 #?(:clj
    ;; Compiler macro for inlining the two constructors
    (alter-meta! #'element* assoc :inline
                 (fn
                   ([tag attrs content meta]
-                   `(Element. ~tag (or ~attrs {}) (remove nil? ~content) ~meta nil))
+                   `(Element. ~tag (or ~attrs {}) (remove nil? ~content) ~meta))
                   ([tag attrs content]
-                   `(Element. ~tag (or ~attrs {}) (remove nil? ~content) nil nil)))))
+                   `(Element. ~tag (or ~attrs {}) (remove nil? ~content) nil)))))
 
 (defn element
   "Create an xml Element from content varargs"
@@ -207,3 +199,12 @@
   "Create a Comment node"
   [content]
   (Comment. content))
+
+(defn map->Element [{:keys [tag attrs content] :as el}]
+  (element* tag attrs content (meta el)))
+
+(defn tagged-element [el]
+  (cond (map? el) (map->Element el)
+        ;; TODO support hiccup syntax
+        :else (throw (ex-info "Unsupported element representation"
+                              {:element el}))))

src/main/clojure/data_readers.clj

@@ -0,0 +1,2 @@
+{xml/ns clojure.data.xml.name/uri-symbol
+ xml/element clojure.data.xml.node/tagged-element}

src/main/clojure/data_readers.cljc

@@ -8,4 +8,6 @@
     (element :foo) {:tag :foo :attrs {} :content []}
     (element (qname "DAV:" "foo")) {:tag (qname "DAV:" "foo") :attrs {} :content []}
     (element :foo {:a "b"}) {:tag :foo :attrs {:a "b"} :content []}
-    (element :foo {:a "b"} "a" "b") {:tag :foo :attrs {:a "b"} :content ["a" "b"]}))
+    (element :foo {:a "b"} "a" "b") {:tag :foo :attrs {:a "b"} :content ["a" "b"]}
+    #?@(:clj ;; wait for https://github.com/clojure/clojurescript/commit/9484a134bdf039c10ec3c26c8aaa3acd0dcd9875
+        [#xml/element {:tag :foo :content ["C"]} {:tag :foo :attrs {} :content ["C"]}])))