MDEV-25501 routine_definition in information_schema.routines loses tablename if it starts with an _ and is not backticked

remove code duplication in Lex_input_stream::scan_ident_middle(),
make sure identifiers are always use the same code path whether
they start form an underscore or not.

mysql-test/main/sp-bugs.result

@@ -130,7 +130,9 @@ Warnings:
 Note	1050	Table 't2' already exists
 DROP DATABASE testdb;
 USE test;
-End of 5.1 tests
+#
+# End of 5.1 tests
+#
 #
 # BUG#13489996 valgrind:conditional jump or move depends on
 # uninitialised values-field_blob
@@ -342,3 +344,26 @@ FOR i IN 1..10 DO
 RETURN 1;
 END FOR
 DROP FUNCTION f1;
+#
+# End of 10.2 tests
+#
+#
+# MDEV-25501 routine_definition in information_schema.routines loses tablename if it starts with an _ and is not backticked
+#
+create table _t1 (a int);
+create procedure p1() select * from _t1;
+show create procedure p1;
+Procedure	sql_mode	Create Procedure	character_set_client	collation_connection	Database Collation
+p1		CREATE DEFINER=`root`@`localhost` PROCEDURE `p1`()
+select * from _t1	latin1	latin1_swedish_ci	latin1_swedish_ci
+select routine_definition from information_schema.routines where routine_schema=database() and specific_name='p1';
+routine_definition
+select * from _t1
+select body, body_utf8 from mysql.proc where name='p1';
+body	body_utf8
+select * from _t1	select * from _t1
+drop procedure p1;
+drop table _t1;
+#
+# End of 10.3 tests
+#

mysql-test/main/sp-bugs.test

@@ -164,7 +164,9 @@ CALL p1();
 DROP DATABASE testdb;
 USE test;
 
---echo End of 5.1 tests
+--echo #
+--echo # End of 5.1 tests
+--echo #
 
 --echo #
 --echo # BUG#13489996 valgrind:conditional jump or move depends on
@@ -371,3 +373,22 @@ DELIMITER ;$$
 SELECT f1();
 SELECT body FROM mysql.proc WHERE db='test' AND specific_name='f1';
 DROP FUNCTION f1;
+
+--echo #
+--echo # End of 10.2 tests
+--echo #
+
+--echo #
+--echo # MDEV-25501 routine_definition in information_schema.routines loses tablename if it starts with an _ and is not backticked
+--echo #
+create table _t1 (a int);
+create procedure p1() select * from _t1;
+show create procedure p1;
+select routine_definition from information_schema.routines where routine_schema=database() and specific_name='p1';
+select body, body_utf8 from mysql.proc where name='p1';
+drop procedure p1;
+drop table _t1;
+
+--echo #
+--echo # End of 10.3 tests
+--echo #

sql/sql_lex.cc

@@ -2161,6 +2161,11 @@ int Lex_input_stream::scan_ident_middle(THD *thd, Lex_ident_cli_st *str,
     yySkip();                  // next state does a unget
   }
 
+  yyUnget();                       // ptr points now after last token char
+  str->set_ident(m_tok_start, length, is_8bit);
+  m_cpp_text_start= m_cpp_tok_start;
+  m_cpp_text_end= m_cpp_text_start + length;
+
   /*
      Note: "SELECT _bla AS 'alias'"
      _bla should be considered as a IDENT if charset haven't been found.
@@ -2170,28 +2175,17 @@ int Lex_input_stream::scan_ident_middle(THD *thd, Lex_ident_cli_st *str,
   DBUG_ASSERT(length > 0);
   if (resolve_introducer && m_tok_start[0] == '_')
   {
-
-    yyUnget();                       // ptr points now after last token char
-    str->set_ident(m_tok_start, length, false);
-
-    m_cpp_text_start= m_cpp_tok_start;
-    m_cpp_text_end= m_cpp_text_start + length;
-    body_utf8_append(m_cpp_text_start, m_cpp_tok_start + length);
     ErrConvString csname(str->str + 1, str->length - 1, &my_charset_bin);
     CHARSET_INFO *cs= get_charset_by_csname(csname.ptr(),
                                             MY_CS_PRIMARY, MYF(0));
     if (cs)
     {
+      body_utf8_append(m_cpp_text_start, m_cpp_tok_start + length);
       *introducer= cs;
       return UNDERSCORE_CHARSET;
     }
-    return IDENT;
   }
 
-  yyUnget();                       // ptr points now after last token char
-  str->set_ident(m_tok_start, length, is_8bit);
-  m_cpp_text_start= m_cpp_tok_start;
-  m_cpp_text_end= m_cpp_text_start + length;
   body_utf8_append(m_cpp_text_start);
   body_utf8_append_ident(thd, str, m_cpp_text_end);
   return is_8bit ? IDENT_QUOTED : IDENT;