test and workaround for libxml in-context parsing bug. closes #362.

ext/nokogiri/xml_node.c

@@ -1171,6 +1171,7 @@ static VALUE in_context(VALUE self, VALUE _str, VALUE _options)
 {
   xmlNodePtr node;
   xmlNodePtr list;
+  xmlNodePtr child_iter;
   xmlNodeSetPtr set;
   xmlParserErrors error;
   VALUE doc, err;
@@ -1196,6 +1197,14 @@ static VALUE in_context(VALUE self, VALUE _str, VALUE _options)
       (int)NUM2INT(_options),
       &list);
 
+  /* make sure parent/child pointers are coherent so an unlink will work properly (#331) */
+  child_iter = node->doc->children ;
+  while (child_iter) {
+    if (child_iter->parent != (xmlNodePtr)node->doc)
+      child_iter->parent = (xmlNodePtr)node->doc ;
+    child_iter = child_iter->next ;
+  }
+
 #ifndef HTML_PARSE_NOIMPLIED
   htmlHandleOmittedElem(1);
 #endif

test/xml/test_document_fragment.rb

@@ -175,6 +175,18 @@ def awesome!
         end
         assert fragment.children.respond_to?(:awesome!), fragment.children.class
       end
+
+      def test_for_libxml_in_context_fragment_parsing_bug_workaround
+        10.times do
+          begin
+            fragment = Nokogiri::XML.fragment("<div></div>")
+            parent = fragment.children.first
+            child = parent.parse("<h1></h1>").first
+            parent.add_child child
+          end
+          GC.start
+        end
+      end
     end
   end
 end