feat: add hook data per-hook mutable state

[josecolella]

Summary

• Add hook_data_for(hook) method to HookContext that provides per-hook isolated mutable state persisting across all hook stages (before → after → error → finally)
• Add spec tests verifying hook_data isolation between hook instances (spec 4.1.5)
• Add spec tests verifying finally hook receives evaluation details on both success and error paths (spec 4.3.8)

Spec References

• Requirement 4.1.5 — hook data per-hook mutable state
• Requirement 4.6.1 — hook data isolation
• Requirement 4.3.8 — finally hook receives evaluation details

Part of the spec compliance roadmap: #220

Test plan

• bundle exec rspec spec/specification/hooks_spec.rb — 22 examples, 0 failures
• bundle exec standardrb — no offenses

🤖 Jose's AI agent

[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 enhances the OpenFeature SDK by implementing a crucial feature for hooks: the ability to maintain mutable state specific to each hook instance throughout its lifecycle. This change ensures that hooks can store and retrieve data across their various stages, improving their utility and adherence to the OpenFeature specification. Accompanying these functional changes are comprehensive tests that validate the correct isolation of this per-hook data and confirm the finally hook's proper reception of evaluation details under both successful and erroneous conditions.

Highlights

• Per-Hook Mutable State: Introduced a hook_data_for(hook) method to HookContext which provides an isolated, mutable hash for each hook instance, allowing state to persist across all hook stages (before, after, error, finally) as per OpenFeature specification 4.1.5 and 4.6.1.
• Hook Data Isolation Tests: Added new spec tests to verify that the hook_data provided by hook_data_for is correctly isolated between different hook instances, ensuring no unintended state leakage.
• Finally Hook Evaluation Details Tests: Implemented spec tests to confirm that the finally hook receives comprehensive evaluation details, including the resolved value on success and default value with error information on failure, aligning with OpenFeature specification 4.3.8.

Changelog

• lib/open_feature/sdk/hooks/hook_context.rb
  • Initialized @hook_data as an empty hash in the constructor.
  • Added hook_data_for(hook) method to return a mutable hash scoped to a specific hook instance using its object_id.
• spec/specification/hooks_spec.rb
  • Added a new context block for Requirement 4.1.5, including tests for per-hook data persistence across stages and isolation between hook instances.
  • Added a new context block for Requirement 4.3.8, including tests to verify that the finally hook receives correct evaluation details on both success and error paths.

Activity

• The pull request author, josecolella, has added new functionality to support per-hook mutable state.
• New spec tests have been added to cover OpenFeature specification requirements 4.1.5, 4.6.1, and 4.3.8.
• The author confirmed that all existing RSpec tests pass and no StandardRB offenses were found.
• The PR description indicates that an AI agent was involved in the process.

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[gemini-code-assist]

Code Review

This pull request introduces a mechanism for hooks to maintain mutable state across their lifecycle stages, along with corresponding specification tests. The implementation in HookContext uses hook.object_id to scope data, which could lead to potential data leakage in long-running applications due to object_id reuse. I've suggested a more robust approach using the hook object itself as the key. The new tests are well-written and cover the intended functionality.

[gemini-code-assist]

Using hook.object_id as a key in the hash can be problematic. While unlikely in short-lived processes, object_ids can be reused by the Ruby garbage collector for new objects after old ones are destroyed. This could lead to data leakage between different hook instances over the lifetime of a long-running application. A more robust approach is to use the hook object itself as the key. Ruby's Hash handles object keys correctly based on their identity, which is safer and more idiomatic.

          @hook_data[hook] ||= {}