Creating a faker instance via `Factroy::create` shares a state with other instances

[michiruf]

Summary

I've run into issues assuming a faker instance created via the factory is isolated from other faker instances.

Versions

	Version
PHP	8.4.12
fakerphp/faker	1.24.1

Self-enclosed code snippet for reproduction

use Faker\Factory;

test('faker should return the same uuid on different instances', function () {
    $f1 = Factory::create();
    $f1->seed(0);

    $f2 = Factory::create();
    $f2->seed(0);

    expect($f1->uuid())->toBe($f2->uuid());
});

Expected output

Test passed

Actual output

Failed asserting that two strings are identical.
Expected :'46d87f7a-fb2f-35f9-a552-02133b0464df'
Actual   :'e72d9fb1-c496-3ce0-bdb5-cb77f63adfb4'

[johnykvsky]

I think this is the way randomizer works internally - you use seed 0 twice, get different results for attempt 1 and 2, but they should be the same all the time. If you run this script 1000 times it will always give you same result as attempt 1 46d87f7a-fb2f-35f9-a552-02133b0464df, and same result as attempt 2 e72d9fb1-c496-3ce0-bdb5-cb77f63adfb4

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 1 week if no further activity occurs. Thank you for your contributions.

[michiruf]

Hi @teal-bauer,

I might not have performed a clean set up, but it seems that the test I provided still failes when using faker from the repo and commit you specified. I tried starsong-consulting@2a4adcd by using

"fakerphp/faker": "dev-fix/instance-isolated-random-state#2a4adcd01ebc6a01c8ce1872023b87f8ece5dd0a",

and

"fakerphp/faker": "dev-fix/instance-isolated-random-state",

with this repo configuration:

{
    "type": "vcs",
    "url": "https://github.com/starsong-consulting/faker-php.git"
}

Kind regards

[teal-bauer]

Hi @michiruf yes I decided to undo the change because there is no way for Faker in the current form to create independent randomness. While newer PHP versions allow creating separate Randomizer instances, PHP core like array_rand will still use (and thus modify) the global MT state, so we'd still need to seed that, which then leads to potential other problems and ... It's quite messy TBH. I put a low priority item on my backlog to come back to this and make a fully deterministic and independent version of Faker, but for now I don't think this is feasible/sensible

[pimjansen]

I dont think it will be in at initial release but i pinned this since it is actually true. I first want to get the first release of 2.x out and then have a look at this.

[johnykvsky]

Nope, you @michiruf are right- just checked this in code, it should return same value, sorry for wrong earlier answer (was just guessing)