Remove specific XML nodes using Clojure

Question

I have the following XML structure:

(def xmlstr
\"
  
    AAA         


        

Answer 1

The Clojure standard APIs provide convenient functions for manipulating XML and other tree structures. Removing (leaf) nodes can be done on depth-first traversal using clojure.walk:

(require '[clojure.xml :as xml]
         '[clojure.walk :as walk])

(def xmlstr
"
  
    AAA
    BBB
    CCC
    AAA
  
")

(def xmldoc (xml/parse (java.io.ByteArrayInputStream. (.getBytes xmlstr))))

(defn tag-matches [item tag]
  (= (:tag item) tag))

(defn content-matches [item to-match]
  ((into #{} to-match)
   (apply str (:content item))))

(defn match-criteria [item to-match]
  (some #(and (tag-matches % :Type)
              (content-matches % to-match))
        (:content item)))

(defn mk-xml-walker [& to-remove]
  (fn [form]
    (if (and (vector? form)
             (some #(tag-matches % :Item) form))
      (filter (complement #(match-criteria % to-remove)) form)
      form)))

(xml/emit (walk/postwalk (mk-xml-walker "B" "C") xmldoc))

For magical one-liners, you may also want to check out Specter which provides a very concise syntax for manipulating nested data structures, like XML.