feat: add getState for StateWrapperImpl

[hannojg]

Summary:

We're trying to pass jsi::Values directly to our view components (and convert them to java/swift types manually). That way we can pass "complex" objects to our views (such as jsi::Objects with NativeState attached, without the need to convert them to e.g. folly::dynamic).

On android we store our complex prop values on the StateWrapperImpl to pass the complex types between c++ and java/kotlin. See an example here:

https://github.com/hannojg/nitro/blob/2378fe7754294c496b2cbcd62f7109529e276427/packages/react-native-nitro-image/nitrogen/generated/android/c%2B%2B/JValueFromStateWrapper.cpp#L21-L23

  const auto& customStateData = dynamic_cast<const ConcreteState<CustomStateData>&>(state);
  CustomStateData data = customStateData.getData();
  std::shared_ptr<HybridTestObjectSwiftKotlinSpec> nativeProp = data.nativeProp;

(And then it might be used in java like this:)
https://github.com/hannojg/nitro/blob/2378fe7754294c496b2cbcd62f7109529e276427/packages/react-native-nitro-image/android/src/main/java/com/margelo/nitro/image/NitroExampleViewManager.java#L31-L38

public Object updateState(@NonNull View view, ReactStylesDiffMap props, StateWrapper stateWrapper) {
   StateWrapperImpl stateWrapperImpl = (StateWrapperImpl) stateWrapper;

    HybridTestObjectSwiftKotlinSpec nativeProp = ValueFromStateWrapper.valueFromStateWrapper(stateWrapperImpl);
    long value = nativeProp.getBigintValue();
    Log.d("NitroExampleViewManager", "Value from state: " + value);

For that we need to be able to access the underlying state, which is what we added in this PR.

Changelog:

[ANDROID] [ADDED] - Added getState method for StateWrapperImpl

Test Plan:

Internal change, just make sure all tests are passing

[javache]

The first const doesn't add any value

Suggested change

	const std::shared_ptr<const State> getState() const;
	std::shared_ptr<const State> getState() const;

[hannojg]

On a second thought, I think returning a const ref might be a better option here to avoid an unnecessary copy?

[javache]

Yes, that's fine too. Although you do have to make sure you don't hold on to the shared_ptr beyond the lifecycle of the StateWrapperImpl then.

[facebook-github-bot]

@javache has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[rubennorte]

The state returned here is mutable, so returning a reference here seems a bit dangerous. We're making some assumptions about the fact that the caller will manage the lifecycle correctly. Maybe it'd be better to just return a copy of the shared pointer.

[hannojg]

alright, agree - let me change!

[facebook-github-bot]

@javache has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@javache merged this pull request in ed36e89.

[react-native-bot]

This pull request was successfully merged by @hannojg in ed36e89

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