What can cause Joomla to show a face and bare error message, even though debug is turned on

Question

I am working on a site that has errors, and debug is turned on in the configuration. But all I see is the image below with a bare error and no context. How can I get the usual debug information?

Answer 1

It means that the template you're using does not render the stack trace in its error layout. To render the stack trace, use Joomla\CMS\Document\ErrorDocument::renderBacktrace() method. The stack trace should be rendered only when debug is enabled to prevent leaking sensitive data. So at a bare minimum this code can be used inside error.php:

<?php if ($this->debug) : ?>
    <?= $this->renderBacktrace() ?>
<?php endif; ?>

The exception may contain previous exceptions. In which case you should also render them. Something like this should work:

<?php if ($this->debug) : ?>
    <?= $this->renderBacktrace() ?>
    <?php // Loop over exceptions ?>
    <?php while ($error = $this->_error->getPrevious()) : ?>
        <?php // Set the previous exception ?>
        <?php $this->setError($error) ?>
        <p><?= htmlspecialchars($error->getMessage(), ENT_QUOTES, 'UTF-8') ?></p>
        <?= $this->renderBacktrace() ?>
    <?php endwhile ?>
    <?php // Restore the original exception ?>
    <?php $this->setError($this->error) ?>
<?php endif ?>