feat: provider wrapper to support state race fix

[toddbaert]

PoC for open-feature/spec#365. This adds a StateManagingProvider interface (opt-in) so providers can own their state and event emissions, fixing the race between SDK-managed state writes and provider-emitted events during/after init. When a provider implements this interface, the SDK reads state directly from the provider and skips its own state writes and event emissions in the init, shutdown, and runtime event paths. Legacy providers that do not implement the interface continue to work exactly as before (SDK manages their state). Not breaking for application-authors or provider-authors.

Companion PoCs:

• JS: feat: provider wrapper to support state race fix #1362
• Java: feat: provider wrapper to support state race fix java-sdk#1892
• Go: feat: provider wrapper to support state race fix go-sdk#487

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a mechanism for providers to manage their own state, which allows for more control and potentially better concurrency. It modifies the 'ProviderWrapper' to respect this new state management, and adds a type guard to identify these new providers. This change aims to address state race conditions and improve the overall reliability of the system.

Highlights

• State Management: Introduces the concept of 'StateManagingProvider' to allow providers to manage their own state, rather than relying on the SDK to maintain shadow state.
• Provider Wrapper Modification: Updates the 'ProviderWrapper' to accommodate state-managing providers, ensuring that status updates are handled correctly based on whether the provider manages its own state.
• Type Guard Implementation: Adds a type guard, 'isStateManagingProvider', to easily identify providers that manage their own state.

Changelog

• packages/shared/src/open-feature.ts
  • Added check for state-managing providers in ProviderWrapper to handle status updates accordingly.
• packages/shared/src/provider/provider.ts
  • Introduced StateManagingProvider interface and isStateManagingProvider type guard.

Activity

• Initial commit of provider wrapper to support state race fix.

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[gemini-code-assist]

Code Review

This pull request introduces a StateManagingProvider interface to allow providers to manage their own state, which should help resolve state-related race conditions. The ProviderWrapper is updated to delegate state management to these providers while preserving backward compatibility. The implementation is logical, and I have one minor suggestion to improve the type safety of the new type guard.

[gemini-code-assist]

Casting to the full StateManagingProvider<S> interface within the type guard that is meant to validate it can be slightly circular. A more precise approach is to cast to a minimal anonymous type that only contains the property being checked. This improves type safety by not over-stating the type before it's fully validated.

Suggested change

	return 'managesState' in provider && (provider as StateManagingProvider<S>).managesState === true;
	return 'managesState' in provider && (provider as { managesState?: boolean }).managesState === true;