Magento 2 : Use plugin / interceptor on abstract class

Question

I am trying to create a plugin that fires after \Magento\Sales\Controller\Adminhtml\Shipment\AbstractShipment\PrintAction::execute.
So I have my plugin setup in di.xml and an afterExecute() method, but it doesn't seem to get fired.
Now I know there are some limitations for plugins, but I can't read anything about abstract classes.
Can plugins / interceptors be used on abstract classes?

Answer 1

Just to answer the real question here: Yes, it is indeed possible to define plugins / interceptors on abstract classes. Doing this works similar to other plugin definitions: An Interceptor class will be generated for each subclass of the abstract class.

Answer 2

Not 100% sure about this, but I think the plugins work for classes that get instantiated.
The object manager instantiates the my\class\Interceptor instead of my\class when there are plugins for that class.
Since the abstract classes never get instantiated you won't have an \Interceptor class generated that should call the plugins.
But...
I assume there is a class that extends \Magento\Sales\Controller\Adminhtml\Shipment\AbstractShipment\PrintAction and that one is actually instantiated and used.
You can try to create the plugin for that class.
Even if that class does not contain the execute method, it is still available (via parent class) so this means you should be able to add a plugin to it.

• Giel Berkers: Thanks for the tip. I moved my intercepter one level 'lower' but it's not yet getting picked up. It picks my plugin, but as soon as magento/framework/Interception/Interceptor.php::146 is executed (which is the call to the original method $result = parent::$method(...array_values($arguments));), the headers already get sent and the PDF is sent. Effectively ignoring my LISTENER_AFTER.
• Marius: maybe you should try an around plugin and call the original method inside your plugin.
• Giel Berkers: Already tried around. Before the callable the code gets executed, but as soon as I place it after the callable it doesn't work. I'm trying to fetch the result of the fileFactory. Could it be that it outputs the header and exits the script? Since I can't find I way to execute code after the PDF generating, I'm now executing it on before (which works) but it feels wrong since I only want to execute the code if I'm sure the PDF generation works.
• Giel Berkers: Got it! Turns out that Magento\Framework\App\Response\Http\FileFactory::create() is checking if $content !== null and if it's not it indeed starts sending headers and (as I suggested) is doing an exit(0), practically making it impossible for plugins to hook into after for this method. I think I'm going to report this as an issue...
• Giel Berkers: Filed: github.com/magento/magento2/issues/7356