Magento 2: Why Does My Custom Controller Generate an Interceptor?

Question

I recently created a basic routing configuration for a test module

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../../lib/internal/Magento/Framework/App/etc/routes.xsd">
    <router id="standard">
        <route id="helloworld" frontName="helloworld">
            <module name="Pulsestorm_Helloworld" />
        </route>
    </router>    
</config>

and then created a controller file at

app/code/Pulsestorm/Helloworld/Controller/Index/Index.php

Everything work as expected -- but I was surprised to discover that Magento had automatically created an interceptor for my new controller.

var/generation/Pulsestorm/Helloworld/Controller/Index/Index/Interceptor.php

I didn't configure any plugins for my controller -- so I'm little confused as to why Magento generated an interceptor.

What makes Magento 2 automatically create an Interceptor for new controllers?

Answer 1

Plugins are defined on interface. So if you define plugin for concrete interface

<type name="Magento\Framework\App\ActionInterface">
    <plugin name="log" type="Magento\Logging\App\Action\Plugin\Log" sortOrder="95"/>
</type>

then plugin will be work on all classes that implements it and IT will generate interceptor proxies for them. That's why Magento 2 will automatically create a interceptor for your controller (that implements Magento\Framework\App\ActionInterface).