XPath compiler support for the preceding axis

lib/oga/xpath/compiler.rb

@@ -376,6 +376,32 @@ module Oga
         end
       end
 
+      # @param [AST::Node] ast
+      # @param [Oga::Ruby::Node] input
+      # @return [Oga::Ruby::Node]
+      def on_axis_preceding(ast, input, &block)
+        orig_input = original_input_literal
+        root       = literal('root')
+        node       = node_literal
+        doc_node   = literal('doc_node')
+
+        root_assign = orig_input.is_a?(XML::Node)
+          .if_true { root.assign(orig_input.root_node) }
+          .else    { root.assign(orig_input) }
+
+        each_node = root.each_node.add_block(doc_node) do
+          compare = doc_node.eq(input).if_true { send_message(:break) }
+
+          match = backup_variable(node, doc_node) do
+            process(ast, node, &block).if_true { yield node }
+          end
+
+          compare.followed_by(match)
+        end
+
+        root_assign.followed_by(each_node)
+      end
+
       # @param [AST::Node] ast
       # @param [Oga::Ruby::Node] input
       # @return [Oga::Ruby::Node]