Create Craft 3 Plugin - Call to a member function getVersion() on null I'm trying to write my own Craft 3 TWIG filter / functions.

For this purpose I created a scaffolding using pluginfactory.io. I did a composer require and composer correctly symlinks the plugin to the Craft project's vendor directory. When I click "Plugins" in the CP it shows my plugin, but when I click "Install" I get the error:

Call to a member function getVersion() on null

caused in /var/www/html/vendor/craftcms/cms/src/services/Plugins.php on line 328 which is

$info = [
  'handle' =&gt; $handle,
  'version' =&gt; $plugin-&gt;getVersion(), // &lt;== Line 328
  'schemaVersion' =&gt; $plugin-&gt;schemaVersion,
  'installDate' =&gt; Db::prepareDateForDb(new \DateTime()),
];


Why? I compared my composer.json with e.g. nystudio107/craft3-pathtools and it's almost identical and I definitely have a version defined in my composer.json.

Why is $plugin null?

Any suggestions?
Shame on me, but maybe still interesting to others who have this problem: I'm using vagrant and the path of my extension was NOT mounted to the vagrant box. That's all. So it simply could not find the files. Maybe a warning by craft would be nice, that it can not load the plugin files

Though I do not understand, why it found the composer.json to read the basic information, which showed up in the Plugins section of Craft...