MDEV-26299: Some views force server (and mysqldump) to generate invalid SQL for their definitions

Do not print illegal table field names for non-top-level SELECT list,
they will not be refered in any case but create problem for parsing
of printed result.

mysql-test/r/view.result

@@ -6876,5 +6876,16 @@ SELECT 1 FROM (SELECT count(((SELECT i1 FROM v1))) FROM v1) dt ;
 drop view v1;
 drop table t1;
 #
+# MDEV-26299: Some views force server (and mysqldump) to generate
+# invalid SQL for their definitions
+#
+create view v1 as
+select * from
+(select
+"12345678901234567890123456789012345678901234567890123456789012345") as t1;
+drop view v1;
+CREATE VIEW v1 AS select `t1`.`12345678901234567890123456789012345678901234567890123456789012345` AS `Name_exp_1` from (select '12345678901234567890123456789012345678901234567890123456789012345') `t1`;
+drop view v1;
+#
 # End of 10.2 tests
 #

mysql-test/t/view.test

@@ -6608,6 +6608,25 @@ SELECT 1 FROM (SELECT count(((SELECT i1 FROM v1))) FROM v1) dt ;
 drop view v1;
 drop table t1;
 
+
+--echo #
+--echo # MDEV-26299: Some views force server (and mysqldump) to generate
+--echo # invalid SQL for their definitions
+--echo #
+
+create view v1 as
+ select * from
+  (select
+  "12345678901234567890123456789012345678901234567890123456789012345") as t1;
+
+let $definition=`select VIEW_DEFINITION from information_schema.views where TABLE_NAME="v1"`;
+
+drop view v1;
+
+eval CREATE VIEW v1 AS $definition;
+
+drop view v1;
+
 --echo #
 --echo # End of 10.2 tests
 --echo #

sql/sql_select.cc

@@ -25804,6 +25804,11 @@ void st_select_lex::print(THD *thd, String *str, enum_query_type query_type)
 
   //Item List
   bool first= 1;
+  /*
+    outer_select() can not be used here because it is for name resolution
+    and will return NULL at any end of name resolution chain (view/derived)
+  */
+  bool top_level= (get_master()->get_master() == 0);
   List_iterator_fast<Item> it(item_list);
   Item *item;
   while ((item= it++))
@@ -25813,7 +25818,8 @@ void st_select_lex::print(THD *thd, String *str, enum_query_type query_type)
     else
       str->append(',');
 
-    if (is_subquery_function() && item->is_autogenerated_name)
+    if ((is_subquery_function() && item->is_autogenerated_name) ||
+        !item->name)
     {
       /*
         Do not print auto-generated aliases in subqueries. It has no purpose
@@ -25822,7 +25828,20 @@ void st_select_lex::print(THD *thd, String *str, enum_query_type query_type)
       item->print(str, query_type);
     }
     else
-      item->print_item_w_name(str, query_type);
+    {
+      /*
+        Do not print illegal names (if it is not top level SELECT).
+        Top level view checked (and correct name are assigned),
+        other cases of top level SELECT are not important, because
+        it is not "table field".
+      */
+      if (top_level ||
+          !item->is_autogenerated_name ||
+          !check_column_name(item->name))
+        item->print_item_w_name(str, query_type);
+      else
+        item->print(str, query_type);
+    }
   }
 
   /*