Fixed bug#10977: No warning issued if a column name is truncated

When an alias is set to a column leading spaces are removed from the alias.
But when this is done on aliases set by user this can lead to confusion.

Now Item::set_name() method issues the warning if leading spaces were removed
from an alias set by user.

New warning message is added.

mysql-test/r/select.result

@@ -3398,3 +3398,8 @@ drop table t1,t2;
 SELECT 0.9888889889 * 1.011111411911;
 0.9888889889 * 1.011111411911
 0.9998769417899202067879
+select 1 as ' a ';
+a 
+1
+Warnings:
+Warning	1466	Leading spaces are removed from name ' a '

mysql-test/t/select.test

@@ -2906,3 +2906,8 @@ drop table t1,t2;
 # Bug #20569: Garbage in DECIMAL results from some mathematical functions
 #
 SELECT 0.9888889889 * 1.011111411911;
+
+#
+# Bug #10977: No warning issued if a column name is truncated
+#
+select 1 as ' a ';

sql/item.cc

@@ -573,6 +573,7 @@ void Item::set_name(const char *str, uint length, CHARSET_INFO *cs)
   }
   if (cs->ctype)
   {
+    uint orig_len= length;
     /*
       This will probably need a better implementation in the future:
       a function in CHARSET_INFO structure.
@@ -582,6 +583,11 @@ void Item::set_name(const char *str, uint length, CHARSET_INFO *cs)
       length--;
       str++;
     }
+    if (orig_len != length && !is_autogenerated_name)
+      push_warning_printf(current_thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+                          ER_REMOVED_SPACES, ER(ER_REMOVED_SPACES),
+                          str + length - orig_len);
+
   }
   if (!my_charset_same(cs, system_charset_info))
   {

sql/sql_yacc.yy

@@ -4060,8 +4060,8 @@ select_item:
 	      YYABORT;
 	    if ($4.str)
             {
-	      $2->set_name($4.str, $4.length, system_charset_info);
               $2->is_autogenerated_name= FALSE;
+	      $2->set_name($4.str, $4.length, system_charset_info);
             }
 	    else if (!$2->name) {
 	      char *str = $1;
@@ -4936,8 +4936,8 @@ udf_expr:
 	{
 	  if ($4.str)
           {
-	    $2->set_name($4.str, $4.length, system_charset_info);
             $2->is_autogenerated_name= FALSE;
+	    $2->set_name($4.str, $4.length, system_charset_info);
           }
 	  else
 	    $2->set_name($1, (uint) ($3 - $1), YYTHD->charset());