Writing custom rules - Are "implements Rule<...>" and getNodeType() equivalent?

[matks]

Hi, I'm creating a set of custom rules for PrestaShop on the repository phpstan-prestashop.

I'd like to help completing the documentation about custom rules and extensions.

Before submitting a PR to expand the doc I need to be sure what I understood about the topic is correct 😁 , can you confirm that

use PhpParser\Node;

/**
 * @implements Rule<Node\Stmt\Class_>
 */
class MyCustomRule implements Rule

and

use PhpParser\Node\Stmt\Class_;

    /**
     * {@inheritdoc}
     */
    public function getNodeType(): string
    {
        return Class_::class;
    }

are equivalent? they tell phpstan "please only call this custom rules on Node whose type is ... is that right?

[ondrejmirtes]

Hello,
you should use both. This helps PHPStan to call the rule only for the Class_ node type:

    public function getNodeType(): string
    {
        return Class_::class;
    }

And this tells PHPStan what TNodeType is on the Rule interface:

/**
 * @implements Rule<Node\Stmt\Class_>
 */
class MyCustomRule implements Rule

The interface:

/**
 * @phpstan-template TNodeType of \PhpParser\Node
 */
interface Rule
{

	/**
	 * @phpstan-return class-string<TNodeType>
	 * @return string
	 */
	public function getNodeType(): string;

	/**
	 * @phpstan-param TNodeType $node
	 * @param \PhpParser\Node $node
	 * @param \PHPStan\Analyser\Scope $scope
	 * @return (string|RuleError)[] errors
	 */
	public function processNode(Node $node, Scope $scope): array;

}

It also means that you don't have to have any PHPDoc above processNode in MyCustomRule and PHPStan will still know that $node is Class_ :) Which is useful when you run PHPStan on the rules themselves (which you should do).

The synchronization between @implements and getNodeType() is also guaranteed because @phpstan-return class-string<TNodeType> is also checked when analysing the rules. See an example of an error: https://phpstan.org/r/a2f43426-a36c-40ad-96ff-0b80e0bc0b2a

[matks]

Such a fast answer!

Thank you, I will submit some PRs for the doc to explain that to other people looking to write their own rules.

Which is useful when you run PHPStan on the rules themselves (which you should do).

I do 😄 https://github.com/PrestaShop/phpstan-prestashop/blob/main/.github/workflows/phpstan.yml

[ondrejmirtes]

I plan to write comprehensive documentation about developing custom extensions :) So you don't have to do that. But thank you.