Revamp compiler "preceding" specs

This also includes some fixes to make this axis behave correctly when
evaluate relative to a document.

lib/oga/xpath/compiler.rb

@@ -352,10 +352,10 @@ module Oga
         node       = node_literal
         doc_node   = literal(:doc_node)
 
-        orig_input.is_a?(XML::Node)
+        input.is_a?(XML::Node).if_true do
-          .if_true { root.assign(orig_input.root_node) }
+          root.assign(input.root_node)
-          .else    { root.assign(orig_input) }
             .followed_by do
+              document_or_node(root).if_true do
                 root.each_node.add_block(doc_node) do
                   doc_node.eq(input)
                     .if_true { self.break }
@@ -365,6 +365,8 @@ module Oga
                 end
               end
             end
+        end
+      end
 
       # @param [AST::Node] ast
       # @param [Oga::Ruby::Node] input

spec/oga/xpath/compiler/axes/preceding_spec.rb

@@ -1,10 +1,9 @@
 require 'spec_helper'
 
 describe Oga::XPath::Compiler do
-  describe 'preceding axis' do
   before do
-      @document = parse(<<-EOF.strip.gsub(/\s+/m, ''))
+    @document = parse(<<-EOF.strip.gsub(/^\s+|\n/m, ''))
-<root>
+<root foo="bar">
   <foo>
     <bar></bar>
     <baz>
@@ -22,18 +21,55 @@ describe Oga::XPath::Compiler do
     @baz3 = @document.children[0].children[1]
   end
 
-    it 'returns a node set containing preceding nodes of root/foo/baz' do
+  describe 'relative to a document' do
-      evaluate_xpath(@document, 'root/foo/baz/preceding::bar')
+    describe 'preceding::*' do
-        .should == node_set(@bar1)
+      it 'returns an empty NodeSet' do
+        evaluate_xpath(@document).should == node_set
+      end
     end
 
-    it 'returns a node set containing preceding nodes for root/baz' do
+    describe 'root/foo/baz/preceding::bar' do
-      evaluate_xpath(@document, 'root/baz/preceding::baz')
+      it 'returns a NodeSet' do
-        .should == node_set(@baz1, @baz2)
+        evaluate_xpath(@document).should == node_set(@bar1)
+      end
     end
 
-    it 'returns a node set containing preceding nodes relative to root/baz' do
+    describe 'root/baz/preceding::baz' do
-      evaluate_xpath(@baz3, 'preceding::baz').should == node_set(@baz1, @baz2)
+      it 'returns a NodeSet' do
+        evaluate_xpath(@document).should == node_set(@baz1, @baz2)
+      end
+    end
+  end
+
+  describe 'relative to an element' do
+    describe 'preceding::root' do
+      it 'returns a NodeSet' do
+        evaluate_xpath(@foo1).should == @document.children
+      end
+    end
+
+    describe 'preceding::baz' do
+      it 'returns a NodeSet' do
+        evaluate_xpath(@baz3).should == node_set(@baz1, @baz2)
+      end
+    end
+  end
+
+  describe 'relative to the root element' do
+    describe 'preceding::*' do
+      it 'returns an empty NodeSet' do
+        evaluate_xpath(@document.children[0]).should == node_set
+      end
+    end
+  end
+
+  describe 'relative to an attribute' do
+    describe 'preceding::*' do
+      it 'returns an empty NodeSet' do
+        root = @document.children[0]
+
+        evaluate_xpath(root.attribute('foo')).should == node_set
+      end
     end
   end
 end