Global API

[NeaguGeorgiana23]

This PR

• Implements the OpenFeatureAPI singleton class, which serves as the primary entry point for the OpenFeature C++ SDK.
• Provides a global access point via GetInstance().
• It implements a method to generate Client instances.

Related Issues

Fixes #29

[gemini-code-assist]

Summary of Changes

Hello @NeaguGeorgiana23, 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 significantly advances the OpenFeature C++ SDK by introducing its foundational API components. It establishes a robust global entry point (OpenFeatureAPI), enables the creation of client instances for feature flag evaluation (ClientAPI), and provides a mechanism for managing global evaluation contexts (GlobalContextManager). These changes are crucial for the SDK's functionality, allowing developers to interact with feature flags and providers in a structured and thread-safe manner, while also addressing a known issue related to the API's core structure.

Highlights

• OpenFeatureAPI Implementation: The core OpenFeatureAPI singleton class has been implemented, serving as the central entry point for the C++ SDK. It provides global access via GetInstance() and methods to generate Client instances.
• ClientAPI Introduction: A new ClientAPI class has been added, which handles client-specific flag evaluation, metadata retrieval, and manages client-level evaluation contexts. It currently supports boolean flag evaluation.
• Global Context Management: The GlobalContextManager singleton has been introduced to manage the global evaluation context for the SDK in a thread-safe manner.
• API Interface Refinements: The OpenFeature interface has been updated, removing SetProviderAndWait overloads with timeout parameters and adding const qualifiers to several Get methods for better API clarity and correctness. A GetProviderStatus method was also added to the interface.
• Provider Repository Shutdown Behavior: The ProviderRepository::Shutdown method now ensures that after all providers are shut down, the repository is reset to its initial state with a default NoopProvider in a ready status.
• Build System and Testing Updates: The .bazelversion has been updated to 7.4.1. New cc_library targets for the introduced API components and corresponding cc_test targets for ClientAPI, GlobalContextManager, and OpenFeatureAPI have been added to the BUILD files.

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[gemini-code-assist]

Code Review

This pull request introduces the core OpenFeatureAPI singleton, which is a significant and well-structured addition to the C++ SDK. The overall design, including the separation of concerns into ClientAPI and GlobalContextManager, is sound and employs good practices for thread safety and API design. My review includes a few suggestions: two critical fixes for the new test files that would otherwise cause build failures, and two medium-severity recommendations to enhance code clarity and efficiency. Overall, this is a solid contribution.

[gemini-code-assist]

The Shutdown() method re-initializes the repository with a NoopProvider. While this is correct for explicit shutdowns via the API, it's inefficient when Shutdown() is called from the ~ProviderRepository() destructor, as the object is about to be destroyed.

A better approach would be to avoid this re-initialization in the destructor. This could be done by parameterizing the Shutdown method. For example:

// In provider_repository.h
void Shutdown(bool reinitialize = true);

// In provider_repository.cpp
ProviderRepository::~ProviderRepository() { 
  Shutdown(false); 
}

void ProviderRepository::Shutdown(bool reinitialize) {
  // ... existing shutdown logic ...
  if (reinitialize) {
    // ... re-initialization logic from lines 119-127 ...
  }
}

Since this change spans multiple files and locations, I'm not providing a direct code suggestion. Please consider this refactoring to improve efficiency and adhere to best practices for destructors.

[oxddr]

LGTM, but let's have #52 and #53 merged first.