Workaround for removed _db, fix backward compatibility without __get

[Fedik]

Summary of Changes

This is redo #37636
Create a _db without use of magic __get.

The magic get changes behavior of the object A LOT, example if any model have created a property "on fly" it crashes.
Like:

class FooBar{
  public function __get($name){ return null; }
}

$c = new FooBar;
$c->_cache[1] = 'foobar';

var_dump($c->_cache[1] ); // Will be NULL instead of "foobar"

That what happen in

joomla-cms/administrator/components/com_modules/src/Model/ModuleModel.php

Lines 676 to 679 in dd91072

	// Convert to the \Joomla\CMS\Object\CMSObject before adding other data.
	$properties = $table->getProperties(1);
	$this->_cache[$pk] = ArrayHelper::toObject($properties, CMSObject::class);

Testing Instructions

Because it is an alternative fix, it still should work as before.
Addittionaly, please test any 3d component, wich use _db in its model.

Documentation Changes Required

As part of #37095

[Fedik]

hm, how to ignore this in PHPCS?

Property name "$_db" should not be prefixed with an
underscore to indicate visibility

[richard67]

hm, how to ignore this in PHPCS?

Property name "$_db" should not be prefixed with an
underscore to indicate visibility

@Fedik You can add your file to the list of exceptions here https://github.com/joomla/joomla-cms/blob/4.2-dev/ruleset.xml#L37 or you can put a comment at the top of your file at the same place as here https://github.com/joomla/joomla-cms/blob/4.2-dev/tests/Unit/bootstrap.php#L13 , but of course with another rule:

// phpcs:disable PSR2.Classes.PropertyDeclaration.Underscore

I would prefer to do it in the XML, but a recent discussion in my closed PR #38168 has shown that at least @HLeithner would prefer to do it in the PHP file but with an explaining comment why it's needed. @laoneo was also involved in the discussion. Maybe they can tell you in which of the 2 ways it shall be done.

[richard67]

@Fedik Will this solve issue #38173 ? Or does it solve only a part?

[Fedik]

Nope, there need separated fix.

[laoneo]

There are a couple of core models which are still using _db like the back end plugins model.