It really would be much better to have single issue commits. It makes testing MUCH easier and also prevents parts of this PR being held up by other parts

• moving $session->clear() which clears the entire session contents - to $session->remove() which deletes the key we were passing in

For the record while this is a correct change, there is a B/C layer in Joomla\CMS\Session\Session::clear() to cover this exact scenario so if the call to $session->clear() with arguments is nuking the entire session data store then this is a bug that should be fixed (preferably with automated tests but seems only a small few are able to provide tests for the 4.0 architecture).

I have tested this item ? unsuccessfully on 76b89dc

Got a fatal error:
Call to a member function getPaths() on null: Class 'Joomla\Plugin\System\Debug\Storage\FileStorage' not found
Latest Nightly Build (10/2/2019)

@ghazal you may need to delete the file libraries/autoload_psr4.php to force it to regenerate with the debug plugin

Can you look at resolving the conflicts so that this can be tested please. Or better still close it and submit new pr for each separate issue

Resolved. Moved debug stuff into a separate PR so this is a single issue pr now

I have tested this item ✅ successfully on bd13b59

I've tested this pr with the components from the Merged PR #21851
as far as I can tell, everything continues to work as it should

System
PHP Build On: Windows NT 10.0 build 18362 (Windows 10) i586
10.1.37-MariaDB
PHP-Version: 7.3.0
Webserver: Apache/2.4.37 (Win32) OpenSSL/1.1.1a PHP/7.3.0
Joomla! Version: Joomla! 4.0.0-alpha12-dev Development [ Amani ] 19-August-2019 13:40 GMT
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36

I have tested this item ✅ successfully on bd13b59

I've tested this pr with the components from the Merged PR #21851
as far as I can tell, everything continues to work as it should

System
PHP Build On: Windows NT 10.0 build 18362 (Windows 10) i586
10.1.37-MariaDB
PHP-Version: 7.3.0
Webserver: Apache/2.4.37 (Win32) OpenSSL/1.1.1a PHP/7.3.0
Joomla! Version: Joomla! 4.0.0-alpha12-dev Development [ Amani ] 19-August-2019 13:40 GMT
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.132 Safari/537.36

I have tested this item ✅ successfully on bd13b59

For me it works as well.

System

PHP 7.2.8 (built: Aug 28 2018 16:32:29) ( NTS )
Firefox 68 on macOS (Mojave)
Mac OS X 10.14.1 (18B75)

Status "Ready To Commit". 1 build failing.

Thanks

To reproduce:

• Get components from #21851
• Install com_helloworld.0.0.1
• Install com_helloworld.0.0.2

1 | () | JROOT\libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php:432
-- | -- | --
2 | Joomla\Database\Mysqli\MysqliStatement->execute() | JROOT\libraries\vendor\joomla\database\src\DatabaseDriver.php:673
3 | Joomla\Database\DatabaseDriver->execute() | JROOT\plugins\installer\override\override.php:407
4 | PlgInstallerOverride->saveOverrides() | JROOT\plugins\installer\override\override.php:191
5 | PlgInstallerOverride->finalize() | JROOT\plugins\installer\override\override.php:273
6 | PlgInstallerOverride->onInstallerAfterInstaller() | JROOT\libraries\src\Plugin\CMSPlugin.php:285
7 | Joomla\CMS\Plugin\CMSPlugin->Joomla\CMS\Plugin\{closure}() | JROOT\libraries\vendor\joomla\event\src\Dispatcher.php:495
8 | Joomla\Event\Dispatcher->dispatch() | JROOT\libraries\src\Application\EventAware.php:111
9 | Joomla\CMS\Application\WebApplication->triggerEvent() | JROOT\administrator\components\com_installer\Model\InstallModel.php:217
10 | Joomla\Component\Installer\Administrator\Model\InstallModel->install() | JROOT\administrator\components\com_installer\Controller\InstallController.php:42
11 | Joomla\Component\Installer\Administrator\Controller\InstallController->install() | JROOT\libraries\src\MVC\Controller\BaseController.php:728
12 | Joomla\CMS\MVC\Controller\BaseController->execute() | JROOT\libraries\src\Dispatcher\ComponentDispatcher.php:146
13 | Joomla\CMS\Dispatcher\ComponentDispatcher->dispatch() | JROOT\libraries\src\Component\ComponentHelper.php:383
14 | Joomla\CMS\Component\ComponentHelper::renderComponent() | JROOT\libraries\src\Application\AdministratorApplication.php:117
15 | Joomla\CMS\Application\AdministratorApplication->dispatch() | JROOT\libraries\src\Application\AdministratorApplication.php:160
16 | Joomla\CMS\Application\AdministratorApplication->doExecute() | JROOT\libraries\src\Application\CMSApplication.php:241
17 | Joomla\CMS\Application\CMSApplication->execute() | JROOT\administrator\includes\app.php:63
18 | require_once() | JROOT\administrator\index.php:36

PHP error log:

PHP Notice:  Undefined index: :preparedArray1 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 412
PHP Notice:  Undefined index: :preparedArray1 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 413
PHP Notice:  Undefined index: :preparedArray2 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 412
PHP Notice:  Undefined index: :preparedArray2 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 413
PHP Notice:  Undefined index: :preparedArray3 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 412
PHP Notice:  Undefined index: :preparedArray3 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 413
PHP Notice:  Undefined index: :preparedArray4 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 412
PHP Notice:  Undefined index: :preparedArray4 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 413
PHP Notice:  Undefined index: :preparedArray5 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 412
PHP Notice:  Undefined index: :preparedArray5 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 413
PHP Notice:  Undefined index: :preparedArray6 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 412
PHP Notice:  Undefined index: :preparedArray6 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 413
PHP Notice:  Undefined index: :preparedArray7 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 412
PHP Notice:  Undefined index: :preparedArray7 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 413
PHP Notice:  Undefined index: :preparedArray8 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 412
PHP Notice:  Undefined index: :preparedArray8 in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 413
PHP Warning:  mysqli_stmt::bind_param(): Number of variables doesn't match number of parameters in prepared statement in \libraries\vendor\joomla\database\src\Mysqli\MysqliStatement.php on line 430

@Quy please test #26464.