[WIP] Add DatePeriod::getEndDate dynamic return type

[Alban-io]

Resolve phpstan/phpstan#5953

[Alban-io]

Currently my test works only because MethodCall is directly the constructor (new DatePeriod($start, $interval, $recurrences))->getEndDate().

Is there a way to retrieve the constructor arguments from this method ?

[staabm]

I think, the object on which the method is called on, is available via https://github.com/nikic/PHP-Parser/blob/99a24b6a556cb2f85c48f62a5311cbc1f8b6eb92/lib/PhpParser/Node/Expr/MethodCall.php#L13

and you might resolve it via the scope to the actual object (like you did with the method arguments)

[Alban-io]

I've already tried it but I couldn't find the constructor arguments types from MethodCall->var only object type 😕

[staabm]

isn't the 3rd arg returned by getRecurrences()?

[Alban-io]

Not really, DatePeriod are 3 constructors :

public __construct(
    DateTimeInterface $start,
    DateInterval $interval,
    int $recurrences,
    int $options = 0
)

public __construct(
    DateTimeInterface $start,
    DateInterval $interval,
    DateTimeInterface $end,
    int $options = 0
)

public __construct(string $isostr, int $options = 0)

The 3rd arg can have three types : null, int, DateTimeInterface.

null or int

public getEndDate(): null
public getRecurrences(): int

DateTimeInterface

public getEndDate(): DateTimeInterface
public getRecurrences(): null

[staabm]

I see. we need to wait for input from Ondrey ;-)

[Alban-io]

I think DynamicMethodReturnTypeExtension may not be the right choice.

Another way :

Create an Type-Specifying Extensions but I feel like they are not available with constructor (New_), only available on Method, StaticMethod and Function.

@ondrejmirtes What is your point of view about that ?

[ondrejmirtes]

What logic you want to implement in a dynamic return type extension for the constructor?

[ondrejmirtes]

Superseded by #951 for now. Feel free to open a new PR with improvements.

[Alban-io]

What logic you want to implement in a dynamic return type extension for the constructor?

More like an MethodTypeSpecifyingExtension to make specify types (TypeSpecifier).

Example with DatePeriod :

By default (without type specification) :

public getEndDate(): ?DateTimeInterface
public getRecurrences(): ?int

based on the type of the third constructor argument, we can specify the return type of the methods (getEndDate, getRecurrences) for object instance

// A
public __construct(
    DateTimeInterface $start,
    DateInterval $interval,
    DateTimeInterface $end,
    int $options = 0
)
// B
public __construct(
    DateTimeInterface $start,
    DateInterval $interval,
    int $recurrences,
    int $options = 0
)
// C
public __construct(string $isostr, int $options = 0)

in the case of the constructor A, we can remove null on getEndDate & and specify getRecurrences will always return null

public getEndDate(): DateTimeInterface
public getRecurrences(): null

inversely for constructor B & C

public getEndDate(): null
public getRecurrences(): int

[ondrejmirtes]

This would require making DatePeriod generic with two template types - for endDate and recurrences count.

[Alban-io]

Is it possible to make conditional return type with PHPStan ?

<?php

/**
 * @template T of int|\DateTimeInterface|null
 */
class TestDatePeriod {

	/** @var T */
	private $value;

	/**
	 * @param T $value
	 */
	public function __construct($value)
	{
		$this->value = $value;
	}

	/**
	 * @psalm-return (T is \DateTimeImmutable ? \DateTimeImmutable : null)
	 * @phpstan-return (T is \DateTimeImmutable ? \DateTimeImmutable : null)
	 */
	public function getEndDate(): ?DateTimeImmutable
	{
		return $this->value instanceof \DateTimeInterface ? new DateTimeImmutable() : null;
	}

	/**
	 * @psalm-return (T is \DateTimeInterface ? null : int)
	 * @phpstan-return (T is \DateTimeInterface ? null : int)
	 */
	public function getRecurrences(): ?int
	{
		return is_int($this->value) ? 0 : null;
	}
}

$intExpected = fn(int $value): int => $value + 1;
$dateExpected = fn(\DateTimeInterface $dateTime): \DateTimeInterface => $dateTime;

$datePeriod = new TestDatePeriod(new DateTimeImmutable());
$dateExpected($datePeriod->getEndDate());
$intExpected($datePeriod->getRecurrences());

$datePeriod = new TestDatePeriod(55);
$dateExpected($datePeriod->getEndDate());
$intExpected($datePeriod->getRecurrences());

$datePeriod = new TestDatePeriod(null);
$dateExpected($datePeriod->getEndDate());
$intExpected($datePeriod->getRecurrences());

[canvural]

@Alban-io Not yet.

[ondrejmirtes]

But you can write a dynamic return type extension for the same purpose.

[Alban-io]

Thanks for your answers

I tried to make an implementation using DynamicStaticMethodReturnTypeExtension

I am able to determine the third argument type, but I can't find how to specify class methods return type

[ondrejmirtes]

You need to write a DatePeriod generic stub that describes return types of thos two metods, and write a DynamicStaticMethodReturnTypeExtension for the constructor that returns different GenericObjectType based on the arguments.

The stub can look like this:

/**
 * @template TEnd of ?DateTimeInterface
 * @template TRecurrences of ?int
 */
class DatePeriod
{

	/**
	 * @return TEnd
	 */
	public function getEndDate()
	{
		
	}

	/**
	 * @return TRecurrences
	 */
	public function getRecurrences()
	{
		
	}
}

[Alban-io]

It seems to work, great 😃 Alban-io@ad22b8b

Do you want a new PR or reopen this one ?

[ondrejmirtes]

Please open a new PR.