CSS parsing support for commas

The lexer already had the basic plumbing in place but apparently I
completely forgot to also implement the required bits in the parser.

Fixes #121

lib/oga/css/parser.rll

@@ -19,7 +19,7 @@
 %terminals T_IDENT T_PIPE T_LBRACK T_RBRACK T_COLON T_SPACE T_LPAREN T_RPAREN;
 %terminals T_MINUS T_EQ T_SPACE_IN T_STARTS_WITH T_ENDS_WITH T_IN T_HYPHEN_IN;
 %terminals T_GREATER T_TILDE T_PLUS T_NTH T_INT T_STRING T_ODD T_EVEN T_DOT;
-%terminals T_HASH;
+%terminals T_HASH T_COMMA;
 
 css
   = selectors
@@ -27,7 +27,24 @@ css
   ;
 
 selectors
-  = selector selectors_follow*
+  = path selectors_follow*
+    {
+      path = val[0]
+
+      val[1].each do |chunk|
+        path = s(:pipe, path, chunk)
+      end
+
+      path
+    }
+  ;
+
+selectors_follow
+  = T_COMMA path { val[1] }
+  ;
+
+path
+  = selector path_follow*
     {
       # Single selector
       if val[1].empty?
@@ -58,7 +75,7 @@ selectors
     }
   ;
 
-selectors_follow
+path_follow
   = T_SPACE selector { val[1] }
   ;
 

spec/oga/css/evaluator/paths_spec.rb

@@ -19,6 +19,10 @@ describe 'CSS selector evaluation' do
       evaluate_css(@document, 'a b').should == node_set(@b1, @b2)
     end
 
+    it 'returns a node set containing the union of multiple paths' do
+      evaluate_css(@document, 'b, ns1|c').should == node_set(@b1, @b2, @c1)
+    end
+
     it 'returns a node set containing namespaced nodes' do
       evaluate_css(@document, 'a ns1|c').should == node_set(@c1)
     end

spec/oga/css/parser/paths_spec.rb

@@ -11,9 +11,18 @@ describe Oga::CSS::Parser do
     end
 
     it 'parses a path using two selectors' do
-      parse_css('foo bar').should == parse_xpath(
-        'descendant::foo/descendant::bar'
-      )
+      parse_css('foo bar').should ==
+        parse_xpath('descendant::foo/descendant::bar')
+    end
+
+    it 'parses two paths separated by a comma' do
+      parse_css('foo, bar').should ==
+        parse_xpath('descendant::foo | descendant::bar')
+    end
+
+    it 'parses three paths separated by a comma' do
+      parse_css('foo, bar, baz').should ==
+        parse_xpath('descendant::foo | descendant::bar | descendant::baz')
     end
   end
 end