Bug: NULL Fields definition not working for MSQLi Forge in Migration due property $_null and $null names difference

[joelsodias]

Describe the bug

Using Migrations, when you define NULL fields, they are not created as NULLable in MariaDB database.

Table definition with 3 fields set up as NULLable

Look at the result table in database, where the 3 fields do not accept NULL

Looking at Database\Forge.php I noticed there is a differente between a protected property $_null in MySQLi\Forge and $null in Database\Forge

Here it is possible to see when the decision depends on the $null property wich is empty

Unfortunately in MySQLi\Forge the property is defined as $_null so it is ignored by Database\Forge

Suggested Solution

As far as I could work on it, it is a simply change $_null to $null in MySQLi\Forge line 92 solves the problem

After the change NULLable filds passed to work as expected.

It still need some additional tests to understand why $_null was written like that, as well as search for any colateral behavior.

CodeIgniter 4 version
Master Branch

Affected module(s)
vendor\codeigniter4\framework\system\Database\MySQLi\Forge.php