Bug#18201: XML: ExtractValue works even if the xml

fragment is not well-formed xml

Problem:
- ExtractValue silently returned NULL if a wrong XML value is passed.
- In some cases "unexpected END-OF-INPUT" error was not detected, and
  a non-NULL result could be returned for a bad XML value.

Fix:
- Adding warning messages, to make user aware why NULL was returned.
- Missing "unexpected END-OF-INPUT" error is reported now.


mysql-test/r/xml.result:
  - Fixing XML systax error in old test
  - Adding test cases.
mysql-test/t/xml.test:
  - Fixing XML systax error in old test
  - Adding test cases.
sql/item_xmlfunc.cc:
  Produce warning in case of XML systax error,
  instead of silentrly returning NULL.
strings/xml.c:
  - Making error messages better looking and clearer:
  It is important because now they're seen in SHOW WARNINGS
  (previously they were used only for debugging purposes).
  - Adding "unexpected END-OF-INPUT" error if after scanning
    closing tag for the root element some input is left
    (previously this error was ignored in a mistake).

1 files changed, 11 insertions, 1 deletions

diff --git a/sql/item_xmlfunc.cc b/sql/item_xmlfunc.cc
index 71900c26c2d..6bbbf67e074 100644
--- a/sql/item_xmlfunc.cc
+++ b/sql/item_xmlfunc.cc
@@ -2563,7 +2563,17 @@ String *Item_xml_str_func::parse_xml(String *raw_xml, String *parsed_xml_buf)
   xml_enter(&p, raw_xml->ptr(), 0);
 
   /* Execute XML parser */
-  rc= my_xml_parse(&p, raw_xml->ptr(), raw_xml->length());
+  if ((rc= my_xml_parse(&p, raw_xml->ptr(), raw_xml->length())) != MY_XML_OK)
+  {
+    char buf[128];
+    my_snprintf(buf, sizeof(buf)-1, "parse error at line %d pos %d: %s",
+                my_xml_error_lineno(&p) + 1,
+                my_xml_error_pos(&p) + 1,
+                my_xml_error_string(&p));
+    push_warning_printf(current_thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+                        ER_WRONG_VALUE,
+                        ER(ER_WRONG_VALUE), "XML", buf);
+  }
   my_xml_parser_free(&p);
 
   return rc == MY_XML_OK ? parsed_xml_buf : 0;