Bug: Migration runner allows a $db but its never passed to the Migration files

[Ukuser36]

PHP Version

8.0

CodeIgniter4 Version

4.3.4

CodeIgniter4 Installation Method

Manual (zip or tar.gz)

Which operating systems have you tested for this bug?

Linux

Which server did you use?

apache

Database

Mysql

What happened?

When running a new MigrationRunner($config, $db); we are allowed to pass in a $db as the second param. However this $db is never passed to the actual migration files which means that it will fall back to the default one when running latest/up/regress etc. Furthermore, it can't be assumed that $db is a group because it could be a custom config.

Steps to Reproduce

1. Create a $group and pass it to $forge = \Config\Database::forge($group);
2. Run a migration file and outtput $this->forge and you'll see it reverts to the default

Expected Output

The migration files should be using the same $db group / config as the Migration runner.

The solution is to:

1. Amend MigrationRunner $instance = new $class(Database::forge($this->db));
2. Within your Migration files add a construct which calls the parent.

	public function __construct($forge = null){
		if ($forge) parent::__construct($forge);
	}

Anything else?

No response

[kenjis]

The migration files should be using the same $db group / config as the Migration runner.

Why do you think so?

Passing a non-default DB group to MigrationRunner seems like a misuse.
Why is it changeable? Only for testing?

See also #7894 (comment)