Bug#16319: XML: extractvalue() returns syntax errors for some functions

mysql-test/r/xml.result:
  Adding test case
mysql-test/t/xml.test:
  Adding test case
sql/item_xmlfunc.cc:
  Adding support for missing XPath function string-length().
  Fixing function lookup to allow functions with one optional arguments
  (i.e. with 0 or 1 arguments)

mysql-test/r/xml.result

@@ -468,6 +468,30 @@ extractValue(@xml, '/a/@b[substring(.,2,1)="1"]')
 select extractValue(@xml, '/a/@b[substring(.,2,1)="2"]');
 extractValue(@xml, '/a/@b[substring(.,2,1)="2"]')
 12 22
+SET @xml='<a><b>b1</b><b>b2</b></a>';
+SELECT extractValue(@xml, '/a/b[string-length("x")=1]');
+extractValue(@xml, '/a/b[string-length("x")=1]')
+b1 b2
+SELECT extractValue(@xml, '/a/b[string-length("xx")=2]');
+extractValue(@xml, '/a/b[string-length("xx")=2]')
+b1 b2
+SELECT extractValue(@xml, '/a/b[string-length("xxx")=2]');
+extractValue(@xml, '/a/b[string-length("xxx")=2]')
+
+SELECT extractValue(@xml, '/a/b[string-length("x")]');
+extractValue(@xml, '/a/b[string-length("x")]')
+b1
+SELECT extractValue(@xml, '/a/b[string-length("xx")]');
+extractValue(@xml, '/a/b[string-length("xx")]')
+b2
+SELECT extractValue(@xml, '/a/b[string-length()]');
+extractValue(@xml, '/a/b[string-length()]')
+b2
+SELECT extractValue(@xml, 'string-length()');
+ERROR HY000: XPATH syntax error: ''
+SELECT extractValue(@xml, 'string-length("x")');
+extractValue(@xml, 'string-length("x")')
+1
 SET @xml='<a b="b11" b="b12" b="b21" b="22"/>';
 select extractValue(@xml,'/a/@b');
 extractValue(@xml,'/a/@b')

mysql-test/t/xml.test

@@ -192,6 +192,20 @@ select extractValue(@xml, '/a/@b[substring(.,1,1)="2"]');
 select extractValue(@xml, '/a/@b[substring(.,2,1)="1"]');
 select extractValue(@xml, '/a/@b[substring(.,2,1)="2"]');
 
+#
+# Bug#16319: XML: extractvalue() returns syntax errors for some functions
+#
+SET @xml='<a><b>b1</b><b>b2</b></a>';
+SELECT extractValue(@xml, '/a/b[string-length("x")=1]');
+SELECT extractValue(@xml, '/a/b[string-length("xx")=2]');
+SELECT extractValue(@xml, '/a/b[string-length("xxx")=2]');
+SELECT extractValue(@xml, '/a/b[string-length("x")]');
+SELECT extractValue(@xml, '/a/b[string-length("xx")]');
+SELECT extractValue(@xml, '/a/b[string-length()]');
+--error 1105
+SELECT extractValue(@xml, 'string-length()');
+SELECT extractValue(@xml, 'string-length("x")');
+
 SET @xml='<a b="b11" b="b12" b="b21" b="22"/>';
 select extractValue(@xml,'/a/@b');
 select extractValue(@xml,'/a/@b[contains(.,"1")]');

sql/item_xmlfunc.cc

@@ -1133,6 +1133,13 @@ static Item *create_func_number(MY_XPATH *xpath, Item **args, uint nargs)
 }
 
 
+static Item *create_func_string_length(MY_XPATH *xpath, Item **args, uint nargs)
+{
+  Item *arg= nargs ? args[0] : xpath->context;
+  return arg ? new Item_func_char_length(arg) : 0;
+}
+
+
 static Item *create_func_round(MY_XPATH *xpath, Item **args, uint nargs)
 {
   return new Item_func_round(args[0], new Item_int((char*)"0",0,1),0);
@@ -1243,9 +1250,11 @@ static MY_XPATH_FUNC my_func_names[] =
   {"substring"        , 9  ,  2 , 3  , create_func_substr},
   {"translate"        , 9  ,  3 , 3  , 0},
 
+
   {"local-name"       , 10 ,  0 , 1  , 0},
   {"starts-with"      , 11 ,  2 , 2  , 0},
   {"namespace-uri"    , 13 ,  0 , 1  , 0},
+  {"string-length"    , 13 ,  0 , 1  , create_func_string_length},
   {"substring-after"  , 15 ,  2 , 2  , 0},
   {"normalize-space"  , 15 ,  0 , 1  , 0},
   {"substring-before" , 16 ,  2 , 2  , 0},
@@ -1849,7 +1858,12 @@ static int my_xpath_parse_FunctionCall(MY_XPATH *xpath)
   for (nargs= 0 ; nargs < func->maxargs; )
   {
     if (!my_xpath_parse_Expr(xpath))
+    {
+      if (nargs < func->minargs)
         return 0;
+      else
+        goto right_paren;
+    }
     args[nargs++]= xpath->item;
     if (!my_xpath_parse_term(xpath, MY_XPATH_LEX_COMMA))
     {
@@ -1859,6 +1873,8 @@ static int my_xpath_parse_FunctionCall(MY_XPATH *xpath)
         break;
     }
   }
+
+right_paren:
   if (!my_xpath_parse_term(xpath, MY_XPATH_LEX_RP))
     return 0;