[6.0] Regression on installer execution

[joeforjoomla]

Steps to reproduce the issue

Install an extension using a install script and the Installer class:

$instanceInstaller = new Installer ();
if (! $instanceInstaller ->install ( $path )) {

}

Expected result

Works

Actual result

The installer now misses the database

System information (as much as possible)

[6.0] alpha 2

Probably related to:

#43792
#43793

Additional comments

Instead than force the extensions code to update, to avoid b/c break better to ensure the database can always be self referenced by the Installer as up to Joomla 5.4

[conseilgouz]

confirmed

[conseilgouz]

maybe just a documentation update : add setDatabase before calling install method. Something like :

$instanceInstaller = new Installer ();
$instanceInstaller->setDatabase($this->db);
if (! $instanceInstaller ->install ( $path )) {

}

[conseilgouz]

or, in libraries/src/installer, update Installer.php so that setDatabase is performed in construct function instead of getInstance

[conseilgouz]

Note : in J5.3, setDatabase was performed in Adapter construct function.
That's missing in the new Installer construct function.

[alikon]

please test #45670