fix(UniqueGenerator): prevent memory exhaustion when chaining unique()->optional()

[teal-bauer]

Fixes memory exhaustion when using unique()->optional()->method() or unique()->valid()->method() chains by adding explicit optional() and valid() methods to UniqueGenerator.

This is the 2.0 branch counterpart to #1028.

When calling $faker->unique()->optional()->safeEmail(), the UniqueGenerator::__call() handler would call optional() on the underlying generator, returning a ChanceGenerator, then attempt to serialize() it for uniqueness tracking. The ChanceGenerator contains a reference to the entire Generator with all providers, causing massive serialized strings and exponential memory growth.

By adding explicit optional() and valid() methods to UniqueGenerator, ChanceGenerator now wraps UniqueGenerator (not the base Generator). When the final method is called, it delegates back to UniqueGenerator, which serializes only the final value (e.g., the email string), not generator objects.

Fixes #1027

[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.

[teal-bauer]

Thank you but not thank you? These bots are so disrespectful.

[localheinz]

I agree, I would remove the bot, but that would require a review from someone else because I cannot merge my own pull requests, @teal-bauer.

[teal-bauer]

Hm, is there any way to revive this repo (if not project) then?

[localheinz]

The general question is whether it makes sense to continue on the path to 2.0, or instead keep this project maintained on the 1.x path.

As of the moment, I would favor the latter to keep the project usable.

[teal-bauer]

I agree. If you look at my fork, I integrated a ton of my patches and tried to go down the 2.x route, but it doesn't seem beneficial enough given the limitations of the PHP engine, so I basically ripped out the 2.x stuff and instead made a hopefully solid 1.x that could become a 2.x just because of all the fixes etc...