LP:995501 - mysqltest attempts to parse Perl code inside a block with false condition, gets confused and throws wrong errors

https://bugs.launchpad.net/maria/+bug/995501

The following test case

let $run = 0;

if ($run)

{

  --perl

  foreach (1)

  {

    print "In perl\n";

  }

  EOF

  SELECT 1;

}

--echo # Done

fails with

mysqltest: At line 9: query 'EOF

SELECT 1' failed: 1064: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'EOF

SELECT 1' at line 1

Reproducible on MariaDB 5.1-5.5, MySQL 5.1-5.6.

The problem, how I understand it from a quick look, is that mysqltest attempts to parse the code even inside --perl / EOF block; but it fails because it doesn't expect any 'foreach'es or other ways to start a block except for 'if' or 'while'; so it does not notice a start of the inner block, and the rest of parsing goes all wrong.

It only happens when the outer block is not to be executed. For example, this works all right:

let $run = 1;

if ($run)

{

  --perl

  foreach (1)

  {

    print "In perl\n";

  }

  EOF

  SELECT 1;

}

--echo # Done

The right approach seems to be totally ignore everything from the beginning of a perl block and till its eof string. Sorry for not providing a patch so far, during the brief investigation I didn't notice an obvious way to fix it, it would require deeper digging from
my side, while maybe somebody else would know right away.

The problem is a bit of pain for writing reasonably complicated test cases, but so far it seems I can work around it, so I'm setting importance to 'Minor' for now.