Magento 2: virtual types plugins

Question

I'm confused by Magento 2 documentation regarding plugins:

It is first said that:

Plugins cannot be used with virtual types

But then it is said that:

You can specify a class, interface, or virtual type as a type name which the plugin observes

Am I missing something or is the documentation contradicting itself ? Can we create plugins for virtual types ?

Answer 1

Plugins will work for virtual type but only if you specify it for parent classes or interfaces, but you cannot specify plugin specific for concrete virtual type

Answer 2

No, plugins on virtual types do not work.

Proof of concept code:

<?php

namespace Training\Example\Model

class Type
{
    public function bar()
    {
        return __CLASS__;
    }
}

Plugin using <type>:

<?php

namespace Training\Example\Model;

class TypePlugin
{
    public function afterBar(Type $subject)
    {
        return __CLASS__;
    }
}

Plugin using <virtualType>:

<?php

namespace Training\Example\Model;

class VirtualTypePlugin
{
    public function afterBar(Type $subject)
    {
        return __CLASS__;
    }
}

DI config:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <virtualType name="Foo" type="Training\Example\Model\Type">
        <plugin name="myfoo" type="Training\Example\Model\VirtualTypePlugin"/>
    </virtualType>
    <type name="Foo">
        <plugin name="yourfoo" type="Training\Example\Model\TypePlugin"/>
    </type>
</config>

Test:

    <?php

namespace Training\Example\Training\Integration;

use Magento\TestFramework\ObjectManager;
use Training\Example\Model\Type;
use Training\Example\Model\VirtualTypePlugin;

class VirtualTypePluginTest extends \PHPUnit_Framework_TestCase
{
    public function testPluginsOnVirtualTypesWork()
    {
        /** @var Type $instance */
        $instance = ObjectManager::getInstance()->create(Type::class);
        $this->assertSame(VirtualTypePlugin::class, $instance->bar());
    }
}

Result:

Failed asserting that two strings are identical.
Expected :Training\Example\Model\VirtualTypePlugin
Actual   :Training\Example\Model\Type