introduce explicit psalm template to enforce type inference and remove psalm baseline

[emnlmn]

Signed-off-by: Emanuele Menon [email protected]

[Jean85]

This is the part that I do not like, you have to fix this manually every time.
Maybe this is due to Validation::failure that says @psalm-return ValidationFailures<T> instead of @psalm-return ValidationFailures<never>?

[emnlmn]

I agree on disliking that part.
Looking further, what i see is that the codomain of Decoders::make is a Validation<A> where A is inferred by the "sum" of the codomain of the Validation::success and Validation::failure.
I guess that the blame is on the Validation::failure sign that has no clue to infer the right type of what is failed to validates here.

A possibile suggested solution is to tight the type of A inferred from the failure method making it explicit.

// Validation.php

...
/**
     * @psalm-template T
     * @psalm-param mixed $value
     * @psalm-param Context $context
     * @psalm-param class-string<T> $of
     * @psalm-param string|null $message
     * @psalm-return ValidationFailures<T>
     *
     * @param mixed $value
     */
    public static function failureT(string $of, $value, Context $context, ?string $message = null): self
    {
        return self::failures(
            [new VError($value, $context, $message)]
        );
    }
...

However, this requires you to make changes to the php-codec library.
I have no clue on how to solve it purely on client side.

[Jean85]

IMHO that's not possibile, even on the lib side: A could be not existing in a case of failure, especially in our case: the VO shouldn't exist in an invalid state, but in that way you're forcing me to create it as invalid.

Maybe you could force the failure to contain a class-string<A>, but it seems clunky.

@ilario-pierbattista WDYT?

[ilario-pierbattista]

I see your point, and I am aware of this issue.

My goal is to have Validation<T> being isomorphic to a generic Either<VError[]. T>.
Maybe I could find a better implementation in other function libraries, such as https://github.com/marcosh/lamphpda .

Btw, class-string<T> won't work in all cases, since it needs to deal also with non-object values.

[ilario-pierbattista]

facile-it/php-codec#36