The following code:

// Clear buffered output at all levels
$callerFunction = static::getCallerFunctionName();

if ($callerFunction === false)
{
  while (ob_get_level())
  {
    ob_end_clean();
  }
}

should be replaced with:

// Clear buffered output at all levels
while (ob_get_level())
{
  ob_end_clean();
}

Ok will do when i'm back at my PC.

Thanks @ethernidee this has just been commited to this PR.

I have tested this item ✅ successfully on 0fda10a

Default template error page should be displayed, as expected.

Tests are failing.

1. JErrorPageTest::testEnsureTheErrorPageIsCorrectlyRendered
   Failed asserting that false matches expected '<title>500 - Testing JErrorPage::render() with RuntimeException</title>Testing JErrorPage::render() with RuntimeException'.

/drone/src/tests/unit/suites/libraries/cms/error/JErrorPageTest.php:79

2. JErrorPageTest::testEnsureTheErrorPageIsCorrectlyRenderedWithThrowables
   Failed asserting that false matches expected '<title>500 - Testing JErrorPage::render() with PHP 7 Error</title>Testing JErrorPage::render() with PHP 7 Error'.

/drone/src/tests/unit/suites/libraries/cms/error/JErrorPageTest.php:123

Such things cannot be tested if buffer is cleared properly. The tests are invalid, imho.

Such things cannot be tested if buffer is cleared properly. The tests are invalid, imho.

What is the point of clearing the buffer there anyway?

Imagine you render Joomla module. First level of buffer capturing is on. Then in module template you write ob_start() for internal subwidget. If any error happens, Joomla will clear second level buffer and leave top of the default template rendered + will add error page html. This is totally wrong. All buffer levels should be cleared before rewriting the whole response, whether it's json or html response.

I faced such situations on working sites and was really surprised.

Makes sense, thanks

The latest commits make sure the test suite passes as it starts the output buffer right after we cleaded it again. Else that thing will fail as the output puffes is clreandend but not restarted.

Excellent solution!

Thanks!