Methods of Strings keep right return type

[h4kuna]

• bug fix
• BC break? no
• doc PR: nette/docs no need

Hello,
The Strings class does not keep incoming type for few method and this implicated, then I have to use helpers in my projects.

For example, in this case variables $a and $b have type string

use Nette\Utils\Strings as NetteStrings;

class Foo {
	/**
	 * @param non-empty-string $nonEmptyString
	 */
	public function __construct(
		public string $emptyString,
		public string $nonEmptyString,
	) {

	}
}

$a = NetteStrings::lower($foo->emptyString);
$b = NetteStrings::lower($foo->nonEmptyString);

\PHPStan\dumpType($a);
\PHPStan\dumpType($b); // string

The methods does not change type from non-empty-string to string.

Now, variable $b keeps type non-empty-string.

final class Strings
{
	/**
	 * @template T of string
	 * @param T $lower
	 * @return T
	 */
	public static function lower(string $lower): string
	{
		/** @var T $v */
		$v = NetteStrings::lower($lower);

		return $v;
	}
}

$a = Strings::lower($foo->emptyString);
$b = Strings::lower($foo->nonEmptyString);

\PHPStan\dumpType($a);
\PHPStan\dumpType($b); // non-empty-string

[dg]

Thanks for the suggestion. You're technically correct that template types would preserve non-empty-string through these methods.

However, I'm a bit hesitant to add this complexity for what seems like a fairly niche use case. In practice, very few projects use non-empty-string annotations extensively, and those that do can easily create their own typed wrappers.

The added template syntax would make the API more complex without much real-world benefit for most users. What do you think - do you have a concrete use case where this is causing significant issues?

[h4kuna]

I didn't find edge case. At this moment I use wrapper only for lower function.

But I can be more specific, phpstan support non-empty-lowercase-string and lowercase-string and use return condition, because template support numeric-string, callable-string, non-falsy-string etc.

But phpstan does not support uppercase-string..., for other methods I would keep the template.

Example:

final class Strings
{
	/**
	 * @return ($s is non-empty-string ? non-empty-lowercase-string : lowercase-string)
	 */
	public static function lower(string $s): string
	{
		return NetteStrings::lower($s);
	}
}

---

I can send a PR only for Strings::lower now, and update the other methods in a few months.

[dg]

Isn't it better to create stub files than wrappers?

[dg]

Thanks for the PR, but I'm closing it. The problem is that the generic template T would preserve types that don't make sense – for example, uppercase-string would be returned as uppercase-string, which is wrong when the method converts to lowercase.