False positives when using method_exists() with a static method

[josephzidell]

Summary of a problem or a feature request

When using method_exists() with a static method, it is giving a false positive error. The PHP documentation clearly highlights this as a valid use-case.

Code snippet that reproduces the problem

https://phpstan.org/r/ddb2e9099834cf325a7917bcd50b42e2

Actual output

Call to an undefined static method Greetings::waveGoodbye().

Expected output

Nothing. Should have no errors

Similar to #323

[ondrejmirtes]

I've been thinking about this and I can't think of any use case for this - why isn't the method defined on Greetings? I don't think you can define it dynamically.

[josephzidell]

It's a simple use-case where the method is optional, and when defined, provides additional functionality. On Jul 22, 2018 1:58 PM, "Ondřej Mirtes" <notifications@github.com> wrote: I've been thinking about this and I can't think of any use case for this - why isn't the method defined on Greetings? I don't think you can define it dynamically. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1267 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABun28WJRY2raPZL-4K4Kja8DkKX2sIIks5uJL1SgaJpZM4VZ75s> .

[ondrejmirtes]

How can you optionally define a static method? On Sun, 22 Jul 2018 at 20:04, Joseph Zidell <notifications@github.com> wrote:

It's a simple use-case where the method is optional, and when defined, provides additional functionality. On Jul 22, 2018 1:58 PM, "Ondřej Mirtes" ***@***.***> wrote: I've been thinking about this and I can't think of any use case for this - why isn't the method defined on Greetings? I don't think you can define it dynamically. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1267 (comment)>, or mute the thread < https://github.com/notifications/unsubscribe-auth/ABun28WJRY2raPZL-4K4Kja8DkKX2sIIks5uJL1SgaJpZM4VZ75s > . — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#1267 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAGZuALqdzQWlyybCYPL4eKzsblt7Mqrks5uJL6XgaJpZM4VZ75s> .

-- Ondřej Mirtes

[josephzidell]

Models in an MVC framework. A model can define this method, allowing special functionality. Any design pattern, really.

[ondrejmirtes]

Can you show me some example code? I don' see how you can optionally define a static method. The method either exists or it doesn't

[josephzidell]

I'm calling this from the parent class, and checking if the child class defined the method.

class Model
{
	public function checkForExcitingFunctionality()
	{
		if (method_exists(static::class, 'exciting')) {
			static::exciting();
		}
	}
}

// boring class
class ProductModel extends Model
{
}

// exciting class
class ImageModel extends Model
{
	public static function exciting()
	{
		echo 'Ooh hoo!!';
	}
}

[ondrejmirtes]

I see. The example with static::class is different one than the one you gave first, and makes more sense. Thanks.

[josephzidell]

Any update on this?

[szepeviktor]

This could also happen in a trait.

if (method_exists(__CLASS__, 'getConstants')) {
    $statuses = self::getConstants('STATUS_');
}

[dereuromark]

Any update?
We also face this issue for valid PHP code:

    protected function assertInitializeExists(string $widgetClassName): void
    {
        if (!method_exists($widgetClassName, 'initialize')) { ... }
    }

[ondrejmirtes]

@dereuromark Can you post full example to phpstan.org? This one does not yield any errors.

[dereuromark]

Maybe because of missing doc block? I will try to provide one later.

[dereuromark]

    /**
     * @param string $widgetClassName
     *
     * @return void
     */
    protected function assertInitializeExists(string $widgetClassName)
    {
        if (!method_exists($widgetClassName, 'initialize')) {
            throw new \Exception(sprintf(
                'Widget %s needs to define and implement custom initialize() method with its custom widget input parameters.',
                $widgetClassName
            ));
        }
    }

is the exact method throwing that error

  Line   src/Spryker/Yves/Kernel/Widget/WidgetFactory.php                    
 ------ -------------------------------------------------------------------- 
  72     Call to function method_exists() with string and 'initialize' will  
         always evaluate to false.     

And PHP docs state it can be object or fqcn class name string, and this code works fine :)

[josephzidell]

bump

[ondrejmirtes]

@josephzidell What does "bump" mean? Either send a pull request with a fix, or wait. Issue is urgent when a lot of people have the same problem, not just because one guy says "bump".

[szepeviktor]

send a pull request with a fix, or wait

Hard to decide!

[marcospassos]

Similar issue here:

// Call to function method_exists() with string and '__invoke' will always evaluate to false.
if (\method_exists($this->name, '__invoke')) {
}

[ondrejmirtes]

There has been a fix of the method_exists error issue: phpstan/phpstan-src#12

But PHPStan will still complain about Call to an undefined static method Greetings::waveGoodbye(). inside the condition. Unfortunately there's not an easy way to represent this in the type system.

[josephzidell]

I've moved on from PHP and am not following this anymore. @ondrejmirtes, should we keep this open for others?

[ondrejmirtes]

Yes, please keep this open, a bug is still a bug.

[keichinger]

I may have found another example where PhpStan is complaining that a certain method doesn't exist, though my example may be a bit extreme 😅

https://phpstan.org/r/eed4b23c-b6e7-424f-87fa-9f88ac7150e3

In this particular case, I've got a very generic Trait that may or may not be used within a class-inheritance. The actual code works flawlessly, it's just that PhpStan is (rightfully) getting confused here :D

Without knowing the internals of PhpStan, I can imagine that fixing this particular case may be an extreme case of „This code is making sure that it's safe to call said method though parent:: doesn't know about it” 😅

[ondrejmirtes]

@keichinger Your problem is unrelated, please open a separate issue.

[justlevine]

Exact same use case here.

Ive got an abstract class ObjectType, whose children can optionally implement various interfaces.

/**
 * Class - ObjectType
 */
abstract class ObjectType {
 	...
	 protected static function get_type_config() : array {
		$config = parent::get_type_config();

		$config['fields'] = static::get_fields();

		if ( method_exists( static::class, 'get_connections' ) ) { // children that implement TypeWithConnections.php
			$config['connections'] = static::get_connections();
		}

		if ( method_exists( static::class, 'get_interfaces' ) ) { // children that implement TypeWithInterfaces.php
			$config['interfaces'] = static::get_interfaces(); 
		}

		return $config;
	}
}

/**
 * Class - Post
 */
class  Post extends ObjectType implements TypeWithConnections {
	...
	public static function get_interfaces() : array {
		return [ 'some config array' ];
	}
}

[acrobat]

I've also a similar problem related to a BC layer needed in our library to support multiple versions of symfony. Although it's not related to static methods in this case

https://phpstan.org/r/c3ccc112-1178-415a-b3e6-dc0e67f8978e

[ondrejmirtes]

@acrobat This makes sense: Call to an undefined method ExceptionEvent::getException(). - you're never checking for existence of that method.

[acrobat]

Hmm good point actually, nevermind 😅

[github-actions]

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