Lex all XPath expressions in a single machine.

This allows literal values such as strings and numbers to be used as function
arguments.

lib/oga/xpath/lexer.rl

@@ -279,34 +279,16 @@ module Oga
           | op_sub
           ;
 
-        # Machine that handles the lexing of data inside an XPath predicate.
-        # When bumping into a "]" the lexer jumps back to the `main` machine.
-        predicate := |*
-          operator;
-          whitespace | slash | lparen | rparen | comma | colon | star;
-
-          string     => emit_string;
-          integer    => emit_integer;
-          float      => emit_float;
-          axis_full  => emit_axis_full;
-          axis_short => emit_axis_short;
-          identifier => emit_identifier;
-
-          ']' => {
-            add_token(:T_RBRACK)
-            fnext main;
-          };
-        *|;
-
         main := |*
           operator;
           whitespace | slash | lparen | rparen | comma | colon | star;
 
-          '[' => {
+          '[' => { add_token(:T_LBRACK) };
-            add_token(:T_LBRACK)
+          ']' => { add_token(:T_RBRACK) };
-            fnext predicate;
-          };
 
+          string     => emit_string;
+          integer    => emit_integer;
+          float      => emit_float;
           axis_full  => emit_axis_full;
           axis_short => emit_axis_short;
           identifier => emit_identifier;

spec/oga/xpath/lexer/calls_spec.rb

@@ -20,12 +20,13 @@ describe Oga::XPath::Lexer do
     end
 
     example 'lex a function call with two arguments' do
-      lex_xpath('count(foo, bar)').should == [
+      lex_xpath('count(/foo, "bar")').should == [
         [:T_IDENT, 'count'],
         [:T_LPAREN, nil],
+        [:T_SLASH, nil],
         [:T_IDENT, 'foo'],
         [:T_COMMA, nil],
-        [:T_IDENT, 'bar'],
+        [:T_STRING, 'bar'],
         [:T_RPAREN, nil]
       ]
     end