Variable "this" has value of null in an "Expression" validation constraint inside an "All" validation constraint #20477

zsolt-racz · 2016-11-10T14:41:48Z

I have possibly found a bug in the Validator component when combining these two constraints: Expression and All. I'm going to show it on an example:

Considering these two classes:

namespace AppBundle;
class ParentClass {

	private $name;
	private $children;

	public function __construct(){
		$this->children = new ArrayCollection();
	}

	public function getName() {
		return $this->name;
	}

	public function setName( $name ) {
		$this->name = $name;
	}

	public function getChildren() {
		return $this->children;
	}

	public function addChild( $child ) {
		$this->children->add($child);
	}
}

and

namespace AppBundle;
class ChildClass {

	private $name;

	public function getName() {
		return $this->name;
	}

	public function setName( $name ) {
		$this->name = $name;
	}

}

With the following validation rules stored in validation.yml:

AppBundle\ParentClass:
    properties:
        children:
            - NotBlank: ~
            - Valid: ~
            - All:
                - Expression:
                    expression: "this.getName() != value.getName()"

AppBundle\ChildClass:
    properties:
        name:
            - NotBlank: ~

I would like to achieve to forbid assigning the parent's name to children. So the getName() method of the parent should return a distinct value from getName() methods of all children.

However after trying to validate an instance of ParentClass constructed like this:

    $validator = $this->get('validator');

    $parent = new ParentClass();
    $parent->setName("foo");

    $child = new ChildClass();
    $child->setName("bar");

    $parent->addChild($child);
    $validator->validate($parent);

A RuntimeException is thrown with the following message:

Unable to get a property on a non-object.

As I figured out, the variable value is correctly assigned to child objects, however the variable this in the expression has a value of null. I would expect a reference to the parent object in this variable, regarding to the documentation:

this: The object being validated (e.g. an instance of BlogPost);

Symfony 3.1.6, PHP 7.0.8, Linux Mint 18

The text was updated successfully, but these errors were encountered:

stof · 2016-11-10T15:11:44Z

this is populated when you apply an Expression constraint on a property of an object, to be able to access the whole object (as value will be the property value).
For class-level constraint, there are only 2 possibilities: assign null, or assign the object, i.e. the same than value (which could be worse as it could hide things).

In your case, getting the ParentClass instance would be wrong. When the All constraint applies the constraints on all items of the array, we are not validating the ParentClass instance. We are validating the array item.

zsolt-racz · 2016-11-15T16:54:35Z

@stof Well, it makes sense and I agree with your reasoning. However I think the variable this should never be null - this is also what the documentation implicitly states.

Also I found out, that the expression variables in class-level constraints are assigned inconsistently depending if they are defined within the All constraint, or outside the All constraint. For example, if I define a class-level constraint like this:

AppBundle\ChildClass:
    constraints:
        - Expression:
            expression: "this == value"

The validation passes, since the expression is evaluated as true. In this case the value of this and the value of value is the same: the ChildClass object.

Then it would be expectable for the next constraint to pass too:

AppBundle\ParentClass:
    properties:
        children:
            - All:
                - Expression:
                    expression: "this == value"

However, it's definitely not, since in this case this gets assigned to null.

I think in both cases, this should hold the reference to the direct parent object, and value should have the same value or be assigned to null.

maximecolin · 2017-01-30T10:18:04Z

I encountered the same bug expecting to access to the object being validated through this but got null.

I think the context should not be lost when All is used. The object being validated is still the parent object.

… constraint (ostrolucky) This PR was merged into the 2.7 branch. Discussion ---------- [Validator] Fix access to root object when using composite constraint | Q | A | ------------- | --- | Branch? | 2.7 | Bug fix? | yes | New feature? | no | BC breaks? | no | Deprecations? | no | Tests pass? | yes | Fixed tickets | #12315, #20477, #21706 | License | MIT | Doc PR | Commits ------- b18cdcf [Validator] Fix access to root object when using composite constraint

javiereguiluz added Bug Unconfirmed Validator labels Nov 10, 2016

carsonbot added the Status: Needs Review label Nov 10, 2016

xabbuh mentioned this issue Feb 23, 2017

Choice assert with callback fails inside the All assert #21 8000 706

Closed

xabbuh removed the Unconfirmed label Mar 5, 2017

ostrolucky mentioned this issue Dec 17, 2017

[Validator] Fix access to root object when using composite constraint #25529

Merged

fabpot closed this as completed Jan 3, 2018

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Variable "this" has value of null in an "Expression" validation constraint inside an "All" validation constraint #20477

Variable "this" has value of null in an "Expression" validation constraint inside an "All" validation constraint #20477

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Variable "this" has value of null in an "Expression" validation constraint inside an "All" validation constraint #20477

Variable "this" has value of null in an "Expression" validation constraint inside an "All" validation constraint #20477

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