Basic parser setup for XPath function calls.

lib/oga/xpath/parser.y

@@ -32,6 +32,7 @@ rule
     | axis
     | string
     | number
+    | call
     ;
 
   node_test
@@ -61,6 +62,16 @@ rule
     | T_AXIS            { s(:axis, val[0]) }
     ;
 
+  call
+    : T_IDENT T_LPAREN T_RPAREN           { s(:call, val[0]) }
+    | T_IDENT T_LPAREN call_args T_RPAREN { s(:call, val[0], *val[2]) }
+    ;
+
+  call_args
+    : xpath                   { val }
+    | xpath T_COMMA call_args { [val[0], *val[2]] }
+    ;
+
   string
     : T_STRING { s(:string, val[0]) }
     ;

spec/oga/xpath/parser/calls_spec.rb

@@ -0,0 +1,28 @@
+require 'spec_helper'
+
+describe Oga::XPath::Parser do
+  context 'function calls' do
+    example 'parse a function call without arguments' do
+      parse_xpath('count()').should == s(:path, s(:call, 'count'))
+    end
+
+    example 'parse a function call with a single argument' do
+      parse_xpath('count(/foo)').should == s(
+        :path,
+        s(:call, 'count', s(:absolute, s(:path, s(:test, nil, 'foo'))))
+      )
+    end
+
+    example 'parse a function call with two arguments' do
+      parse_xpath('count(/foo, "bar")').should == s(
+        :path,
+        s(
+          :call,
+          'count',
+          s(:absolute, s(:path, s(:test, nil, 'foo'))),
+          s(:path, s(:string, 'bar'))
+        )
+      )
+    end
+  end
+end