Bug#18170: XML: ExtractValue(): XPath expression can't use QNames (colon in names)

Problem source:
Qualified names (aka QName) didn't work as tag names and attribute names,
because the parser lacked a real rule to scan QName, so it understood
only non-qualified names without prefixes.

Solution:
New rule was added to check both "ident" and "ident:ident" sequences.

mysql-test/r/xml.result

@@ -641,3 +641,12 @@ CALL p2();
 EXTRACTVALUE(p,'/Ñ/r')
 A
 DROP PROCEDURE p2;
+select extractValue('<ns:element xmlns:ns="myns"/>','count(ns:element)');
+extractValue('<ns:element xmlns:ns="myns"/>','count(ns:element)')
+1
+select extractValue('<ns:element xmlns:ns="myns">a</ns:element>','/ns:element');
+extractValue('<ns:element xmlns:ns="myns">a</ns:element>','/ns:element')
+a
+select extractValue('<ns:element xmlns:ns="myns">a</ns:element>','/ns:element/@xmlns:ns');
+extractValue('<ns:element xmlns:ns="myns">a</ns:element>','/ns:element/@xmlns:ns')
+myns

mysql-test/t/xml.test

@@ -321,3 +321,11 @@ END//
 DELIMITER ;//
 CALL p2();
 DROP PROCEDURE p2;
+
+#
+# Bug#18170: XML: ExtractValue():
+# XPath expression can't use QNames (colon in names)
+#
+select extractValue('<ns:element xmlns:ns="myns"/>','count(ns:element)');
+select extractValue('<ns:element xmlns:ns="myns">a</ns:element>','/ns:element');
+select extractValue('<ns:element xmlns:ns="myns">a</ns:element>','/ns:element/@xmlns:ns');

sql/item_xmlfunc.cc

@@ -2266,6 +2266,30 @@ static int my_xpath_parse_Number(MY_XPATH *xpath)
 }
 
 
+/*
+  QName grammar can be found in a separate document
+  http://www.w3.org/TR/REC-xml-names/#NT-QName
+
+  [6] 	QName     ::= (Prefix ':')? LocalPart
+  [7] 	Prefix    ::= NCName
+  [8] 	LocalPart ::= NCName
+*/
+static int
+my_xpath_parse_QName(MY_XPATH *xpath)
+{
+  const char *beg;
+  if (!my_xpath_parse_term(xpath, MY_XPATH_LEX_IDENT))
+    return 0;
+  beg= xpath->prevtok.beg;
+  if (!my_xpath_parse_term(xpath, MY_XPATH_LEX_COLON))
+    return 1; /* Non qualified name */
+  if (!my_xpath_parse_term(xpath, MY_XPATH_LEX_IDENT))
+    return 0;
+  xpath->prevtok.beg= beg;
+  return 1;
+}
+
+
 /*
   Scan Variable reference
 
@@ -2299,7 +2323,7 @@ my_xpath_parse_VariableReference(MY_XPATH *xpath)
 static int
 my_xpath_parse_NodeTest_QName(MY_XPATH *xpath)
 {
-  if (!my_xpath_parse_term(xpath, MY_XPATH_LEX_IDENT))
+  if (!my_xpath_parse_QName(xpath))
     return 0;
   DBUG_ASSERT(xpath->context);
   uint len= xpath->prevtok.end - xpath->prevtok.beg;