Interceptor not working when calling parent::method()

[milansimek]

Preconditions

Magento 2.1.7 + PHP 7.0.22

Steps to reproduce

1. Create the following structure:

class A {
  public function doSomething(){
     echo 'I do something! (original)';
  }
}

class B extends class A {
  public function parentDoSomething(){
     parent::doSomething();  
  }
}

2. Now create an around plugin for the class A doSomething method:

public function aroundDoSomething(\Namespace\A $subject, callable $proceed){
        echo 'I do something else! (plugin)';
}

3. Now execute $classB->parentDoSomething();

Expected result

I do something else! (plugin) should be printed

Actual result

I do something! (original) is printed

Other information

Calling $this->doSomething() in class B does produce the correct result.

[magento-engcom-team]

@milansimek, thank you for your report.
We've created internal ticket(s) MAGETWO-83669 to track progress on the issue.

[magento-engcom-team]

Hi @lisovyievhenii. Thank you for working on this issue.
Looks like this issue is already verified and confirmed. But if your want to validate it one more time, please, go though the following instruction:

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[lisovyievhenii]

@milansimek ,

Plugin will never work on "parent" call.
At first, "parent" means you want to call parent method immediately. Let's imagine class:

class B extends A {
    public function doSomething(){
        ....
        //some code manipulations
        ....
        parent::doSomething();
        ....
        //some code manipulations after parent code is finished
    }
}

Here I have class B that realize method doSomething. It makes some actions, then calls parent method.

So what would be if plugin will work as you want? As the result we will call B->doSomething() that is wrapped by Interceptor class. Plugin will work, then B->doSomething() will run, and when parent::doSomething() will be called the plugin again will wrap doSomething and we will have a recursive plugin's execution.

Explanation why Magneto doesn't wrap parent method:
you have class A and a plugin for it. Everything works fine - Interceptor extends class A and wraps its functions.
Then you created class B that extends A and call B somewhere in your code (like $b = new B()). Magento will create an Interceptor for class B, but as you can see B extends A, not Interceptor of A.
So in case if you call $b->doSomething(), plugin will be called, because you didn't overridden it
In case if you call $b->parentDoSomething(), plugins on parentDoSomething method will be called. BUT you call a parent method there, so you want to execute a parent's method of class A. Interceptor doesn't have a wrapping method for parent, only for B's method.

So if you are really want to have a plugin to be called on parent method, you can:

1. extend your class B from Interceptor of the class A - very ugly solution
2. in the method parentDoSomething call $this, not parent

[milansimek]

@lisovyievhenii Thanks for your response!

Since I'm using an "around" plugin and not proceeding with the execution, the code acts more as a rewrite of the original method. This means there won't be any recursive execution issues.

Also, in your example you changed the method name that calls the parent method from parentDoSomething to doSomething. Of course that would cause an infinite loop when continuing execution, but my example uses a different method name which calls the parent method.

I appreciate your recommendation regarding using $this instead of parent, but that's not possible when dealing with Magento 2.x code which in many cases hasn't been rewritten and has just been ported from Magento 1.x. As an extension developer, I can't change the core files of course.

To ensure flexibility and no unexpected behavior when using interceptors, it would be more logical if all calls to a specific class method can be intercepted. This is obviously a limitation in the current system.

If it's not possible to intercept parent:: calls, in many cases it will be required to completely rewrite the class which uses the parent:: call. This in turn forces you to duplicate a lot of code, especially when it comes to the ported legacy M1 classes, since these often are very tightly coupled and use multiple parent:: calls in a single huge class method.

If this parent method is being called in 4 different child classes with each method being 20 lines or longer for example, you'd have to create a plugin for each child method, completely copy and rewrite those methods without the possibility to access private properties in a clean way. This will result in a complete unreadable code mess as you can probably imagine.

Of course in an ideal world the Magento 2 core code should be clean and easy to extend with interceptors. Each class method should by tiny and easy to modify / extend. This just isn't the case with the current state of a lot of core modules integrated in Magento 2.

On a side note: When duplicating too much code, extensions submitted won't pass the Marketplace code duplication test.

[milansimek]

So what would be if plugin will work as you want? As the result we will call B->doSomething() that is wrapped by Interceptor class. Plugin will work, then B->doSomething() will run, and when parent::doSomething() will be called the plugin again will wrap doSomething and we will have a recursive plugin's execution.

This isn't what I'm trying to achieve:

Actually, I'd like to create an interceptor for A::doSomething, not B::doSomething. So B->doSomething() will be called, which in turn calls the parent method. Then then interceptor should kick in and wrap around the A::doSomething method.

A::doSomething doesn't call any parent methods since it's already the method of the parent class. So this shouldn't be an issue I think?

Maybe I'm missing something, if that's the case please let me know.

Thanks!

[lisovyievhenii]

Hello @milansimek ,

When some method calls parent::doSomething, it says to the PHP interpreter to call the parent method (without any possibility to catch this call).
So to do what you want (Interceptor should wrap parent::doSomething), you need to rewrite PHP interpreter.
I guess this feature will never be in Magento.

But seriously, if you need to do some changes in methods, which are called by parent keyword, there are only few ways to modify that parent method: override original class with "preference" in di.xml; create a patch; make an around plugin on child classes, which calls parent method and override all logic and the worst solution - keep Magento code in project/app/Magento and make you changes here.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 14 days if no further activity occurs. Is this issue still relevant? If so, what is blocking it? Is there anything you can do to help move it forward? Thank you for your contributions!