Loader's convert()-getDom() returning an empty array on a stock Mage 2.4.3 install.

[dotancohen]

On a bone stock 2.4.3 install I added a single Product. I then cleared the cache from Settings, but upon page reload I got this error:

1 exception(s):
Exception #0 (Exception): Notice: Undefined index:  in /var/www/pix/vendor/magento/framework/Module/ModuleList/Loader.php on line 99

Exception #0 (Exception): Notice: Undefined index:  in /var/www/pix/vendor/magento/framework/Module/ModuleList/Loader.php on line 99
<pre>#1 Magento\Framework\Module\ModuleList\Loader->load() called at [vendor/magento/framework/Module/ModuleList.php:72]
#2 Magento\Framework\Module\ModuleList->getAll() called at [vendor/magento/framework/Module/ModuleList.php:91]
#3 Magento\Framework\Module\ModuleList->getOne() called at [vendor/magento/framework/Module/DbVersionInfo.php:144]
#4 Magento\Framework\Module\DbVersionInfo->isModuleVersionEqual() called at [vendor/magento/framework/Module/DbVersionInfo.php:59]
#5 Magento\Framework\Module\DbVersionInfo->isSchemaUpToDate() called at [vendor/magento/framework/Module/DbVersionInfo.php:103]
#6 Magento\Framework\Module\DbVersionInfo->getDbVersionErrors() called at [vendor/magento/framework/Module/Plugin/DbStatusValidator.php:119]
#7 Magento\Framework\Module\Plugin\DbStatusValidator->getGroupedDbVersionErrors() called at [vendor/magento/framework/Module/Plugin/DbStatusValidator.php:53]
#8 Magento\Framework\Module\Plugin\DbStatusValidator->beforeDispatch() called at [vendor/magento/framework/Interception/Interceptor.php:121]
#9 Magento\Framework\App\FrontController\Interceptor->Magento\Framework\Interception\{closure}() called at [vendor/magento/framework/Interception/Interceptor.php:153]
#10 Magento\Framework\App\FrontController\Interceptor->___callPlugins() called at [generated/code/Magento/Framework/App/FrontController/Interceptor.php:23]
#11 Magento\Framework\App\FrontController\Interceptor->dispatch() called at [vendor/magento/framework/App/Http.php:116]
#12 Magento\Framework\App\Http->launch() called at [vendor/magento/framework/App/Bootstrap.php:264]
#13 Magento\Framework\App\Bootstrap->run() called at [pub/index.php:29]
</pre>

Thinking that it is related to the cache I cleared all caches and indexes via bin/magento (yes, I know that the PHP error message isn't referring to those indexes), but the error persists. Debugging, I see that the vendor/magento/framework/Module/ModuleList/Loader.php's method load() runs this code:

$data = $this->converter->convert($this->parser->getDom());
$name = key($data);
if (!isset($excludeSet[$name])) {
    $result[$name] = $data[$name];
}

After 343 iterations the last valid $name is Magento_ComposerRootUpdatePlugin, the iteration after that returns $name as null. Thus, the reading of $data[$name] throws the exception seen above.

Hours of trying to debug why convert()-getDom() is returning null have brought me here. )) Why might this be happening? What can I do to repair this install?

Thank you.

[dotancohen · Accepted solution]

Resolution: The problem was a typo in the XML of the next iteration. Probably a consequence of thinking that I'm proficient in VIM. The module whose XML was invalid was not yet committed to git, so I did not notice the change.

Lesson: Commit early, commit often.