Backport noDoubleEncoding fix from xmlbuilder2.

See: oozcitak/xmlbuilder2#16

src/XMLStringifier.coffee

@@ -162,7 +162,7 @@ module.exports = class XMLStringifier
   # `str` the string to escape
   textEscape: (str) ->
     if @options.noValidation then return str
-    ampregex = if @options.noDoubleEncoding then /(?!&\S+;)&/g else /&/g
+    ampregex = if @options.noDoubleEncoding then /(?!&(lt|gt|amp|apos|quot);)&/g else /&/g
     str.replace(ampregex, '&')
        .replace(/</g, '&lt;')
        .replace(/>/g, '&gt;')
@@ -175,7 +175,7 @@ module.exports = class XMLStringifier
   # `str` the string to escape
   attEscape: (str) ->
     if @options.noValidation then return str
-    ampregex = if @options.noDoubleEncoding then /(?!&\S+;)&/g else /&/g
+    ampregex = if @options.noDoubleEncoding then /(?!&(lt|gt|amp|apos|quot);)&/g else /&/g
     str.replace(ampregex, '&amp;')
        .replace(/</g, '&lt;')
        .replace(/"/g, '&quot;')

test/issues/97.coffee

@@ -1,24 +1,24 @@
 obj =
   root:
-    '@att': 'attribute value with # and #'
-    '#text': 'HTML entities for umlaut are ü and ü.'
+    '@att': 'attribute value with & and &'
+    '#text': 'XML entities for ampersand are & and &.'
 
 suite 'Tests specific to issues:', ->
   test 'Issue #97 (No double encoding)', ->
     eq(
       xml(obj, { noDoubleEncoding: true }).end()
       '<?xml version="1.0"?>' +
-      '<root att="attribute value with &num; and &#35;">' +
-        'HTML entities for umlaut are &uuml; and &#252;.' +
+      '<root att="attribute value with &amp; and &amp;#38;">' +
+        'XML entities for ampersand are &amp; and &amp;#38;.' +
       '</root>'
     )
 
   test 'Issue #97 (Double encoding - default behavior)', ->
     eq(
       xml(obj).end()
       '<?xml version="1.0"?>' +
-      '<root att="attribute value with &amp;num; and &amp;#35;">' +
-        'HTML entities for umlaut are &amp;uuml; and &amp;#252;.' +
+      '<root att="attribute value with &amp;amp; and &amp;#38;">' +
+        'XML entities for ampersand are &amp;amp; and &amp;#38;.' +
       '</root>'
     )