feat(option): new Option::merge() method

[devnix]

The idea, as shown, is easy.

I propose a versatile merge method to make several operations easier between two Options:

Option\some(1)->merge(Option\some(2), static fn (int $a, int $b) => $a + $b)); // Option<3>
Option\none()->merge(Option\some(2), static fn (int $a, int $b) => $a + $b)); // Option<*never*>
Option\some(1)->merge(Option\none(), static fn (int $a, int $b) => $a + $b)); // Option<*never*>

Option\some('Hello')->merge(
    Option\some('World'), 
    static fn (string $a, string $b) => $a.' '.$b)
); // Option<"Hello World">

This is what triggered this particular need in my case:

$value1 = Option\some(false);
$value2 = Option\some(true);

$value1->merge($value2, static fn (bool $a, bool $b) => $a && $b)->unwrapOr(false); // false

$value1 = Option\some(Money::EUR(100));
$value2 = Option\some(Money::USD(100));

$value1->merge($value2, static fn (Money $a, Money $b) => $a->equals($b))->unwrapOr(false); // false

Probably there is a better name for this method, for sure!

[coveralls]

Pull Request Test Coverage Report for Build 6562143288

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 98.999%

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Totals
Change from base Build 6487837444:	0.0%
Covered Lines:	4155
Relevant Lines:	4197

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💛 - Coveralls

[devnix]

I'm unsure about those mutation test errors. Any change in my branch does not cause them, am I right?

[veewee]

Looks like a nice feature. Haven't jumped in the code yet, but was thinking about the name in line of $option->combineWith($other, $closure). WDYT?

[devnix]

I was thinking along the lines of using a short name, join was a candidate I was thinking of too. To me, and/andThen was the nicer options here

[veewee]

I'm unsure about those mutation test errors. Any change in my branch does not cause them, am I right?

I was looking at the mutation errors in #427. Gonna continue somewhere next week most likely.

[veewee]

@devnix can you rebase against the next branch to get the github actions green again?
I was thinking about naming it compose() this morning. What do you think about that one?

[devnix]

Hi @veewee! I've been playing with Rust for the last couple of weeks, and I've found that Option has a zip method that may be useful for this purpose. Instead of requiring a callback to join two Some values into one like my idea, it creates a tuple if both are Some. Check this example: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=bf6a95e1e06b98093c114a274a6e0fe6

My original proposal would be something like zip_with I guess, which is currently experimental, and equivalent to .zip().map(). I could provide the implementation of both if you are ok with that, but I'm unsure about how to represent this tuple in php/phpdoc. Also, maybe the unzip method would be interesting too?

[veewee]

Just looked at the rust documentation and that indeed seems the way to go and the naming to use here. Feel free to provide all 3 of those functions.
Type-hinting tuples can be done with array{0: A, 1: B} iirc.

https://psalm.dev/r/06049ede28

[devnix]

Superseded by #434