Bug #18172 XML: Extractvalue() accepts mallformed

  XPath without a XPath syntax error
item_xmlfunc.cc:
  Error message didn't happen because after
  a failing attempt to parse RelativeLocationPath,
  my_xpath_parse_AbsoluteLocationPath() returned success.
  Changeing logic a bit:
  - Try to parse EOF first, return success if true.
  - Then try to parse RelativeLocationPath(), return success if true.
  - Otherwise return failure.
xml.result:
  Adding test case.
  Also, this change made it possible to generate 
  an error message earlier in the case of another
  bad XPATH syntax.
xml.test:
  Adding test case.

mysql-test/r/xml.result

@@ -546,7 +546,7 @@ select extractvalue('<a>a<b>B</b></a>','a|/b');
 extractvalue('<a>a<b>B</b></a>','a|/b')
 a
 select extractvalue('<a>A</a>','/<a>');
-ERROR HY000: XPATH syntax error: '>'
+ERROR HY000: XPATH syntax error: '<a>'
 select extractvalue('<a><b>b</b><b!>b!</b!></a>','//b!');
 ERROR HY000: XPATH syntax error: '!'
 select extractvalue('<a>A<b>B<c>C</c></b></a>','/a/descendant::*');
@@ -613,3 +613,5 @@ select extractValue('<e>1</e>','position()');
 ERROR HY000: XPATH syntax error: ''
 select extractValue('<e>1</e>','last()');
 ERROR HY000: XPATH syntax error: ''
+select extractValue('<e><a>1</a></e>','/e/');
+ERROR HY000: XPATH syntax error: ''

mysql-test/t/xml.test

@@ -286,3 +286,12 @@ select extractvalue('<a>Jack</a>' collate latin1_bin,'/a[contains(../a,"j")]');
 select extractValue('<e>1</e>','position()');
 --error 1105
 select extractValue('<e>1</e>','last()');
+
+
+#
+# Bug #18172 XML: Extractvalue() accepts mallformed
+# XPath without a XPath syntax error
+#
+--error 1105
+select extractValue('<e><a>1</a></e>','/e/');
+

sql/item_xmlfunc.cc

@@ -1561,10 +1561,13 @@ static int my_xpath_parse_AbsoluteLocationPath(MY_XPATH *xpath)
     return my_xpath_parse_RelativeLocationPath(xpath);
   }
 
+  if (my_xpath_parse_term(xpath, MY_XPATH_LEX_EOF))
+    return 1;
+
   if (my_xpath_parse_RelativeLocationPath(xpath))
     return 1;
 
-  return 1;
+  return 0;
 }