With and without Patch didn't get a Notice.

@franz-wohlkoenig
Have you looked at the php_error.log file as this Notice is not going to display in the browser window?

The easiest way to see error is adding this command

die();

after this line https://github.com/joomla/joomla-cms/blob/staging/administrator/components/com_config/model/application.php#L387

@infograf768

I think $data['cache_path'] is always available, so actually, to prevent the notice, we only have to check !empty($prev['cache_path'])

So the code would become:

if ($data['cache_path'])
{
	$path = $data['cache_path'];
}
elseif (!$data['cache_path'] && !empty($prev['cache_path']))
{
	$path = $prev['cache_path'];
}
else
{
	$path = JPATH_SITE . '/cache';
}

Or even simpler

if ($data['cache_path'])
{
	$path = $data['cache_path'];
}
elseif (!empty($prev['cache_path']))
{
	$path = $prev['cache_path'];
}
else
{
	$path = JPATH_SITE . '/cache';
}

I don't see the need for checking !$data['cache_path'] in else if block.

I have tested this item ✅ successfully on b344bf3

thanks for helping, @joomdonation

You're welcome @franz-wohlkoenig . If @infograf768 agree with my suggested changes, we will need your help re-test this PR again.

will do.

@franz-wohlkoenig @joomdonation Simplified as suggested, please test again.

I have tested this item ✅ successfully on b069f82

@infograf768 Thanks for making the changes. I marked the test result.

1. Tested with PR got a blank Site,
2. tested without PR got Notice: Undefined index: cache_path in /var/www/web17/html/Joomla/administrator/components/com_config/model/application.php on line 290

Maybe cause couldn't install todays nightly build (Download of update package failed.).

Blank site? Before you press save or after pressing save? Maybe it is blank because you added die(); command?

After pressing save. Maybe because of die(); but to see the Notice isn't it helpful?

Yes. The die(); command is used to allow you to see notice before patch. After patch, you see blank screen means no notice anymore

So for now, you should remove the die(); command, then save the configuration again. If configuration (especially cache path) is being saved, then you can mark the test result as success

I have tested this item ✅ successfully on b069f82

@joomdonation haven't known that there's a beta1 and custom-path-update didn't work. After installing beta1 test was sccessfully.

Sorry, I was wrong. The code looks OK

@joomdonation
I suggest you create a new PR as this one deals only with the Notice. And tag @mbabker as he is the one who created the original PR.
I mark this one as RTC

RTC. Thanks.