feat(flagd): use flagd-evaluator (rust unified implementation) for python - POC - java uses the same with wasm

[aepfli]

This PR

• adds this new feature

Related Issues

Fixes #1234523

Notes

Follow-up Tasks

How to test

[gemini-code-assist]

Summary of Changes

Hello @aepfli, 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 represents a significant architectural shift in the Python flagd provider by integrating a native Rust-based flag evaluator. This change aims to enhance performance and standardize the flag evaluation mechanism across different language SDKs. The update involves replacing the Python-based in-process resolver with a new WasmInProcessResolver that leverages the native evaluator, streamlining the targeting logic, and updating project dependencies accordingly.

Highlights

• Native Flag Evaluation: The core flag evaluation logic has been migrated from a Python-based implementation to a native Rust-based flagd-evaluator for improved performance and consistency with other language SDKs (e.g., Java uses WASM for the same evaluator).
• Dependency Updates: Outdated Python dependencies related to the previous evaluation logic (mmh3, panzi-json-logic, semver) have been removed, and the new flagd-evaluator package has been added.
• New Resolver Implementation: A new WasmInProcessResolver has been introduced, which directly utilizes the flagd-evaluator for all in-process flag resolution, replacing the older Python-based InProcessResolver.
• Targeting Logic Refactor: The targeting.py module has been completely refactored to remove custom Python operators and json_logic, instead delegating all targeting rule evaluation to the native flagd-evaluator.
• Test Suite Updates: Existing test files (test_errors.py and test_targeting.py) that were specific to the previous Python-based evaluation logic have been removed, reflecting the shift to the native evaluator.

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[gemini-code-assist]

Code Review

This pull request introduces a proof-of-concept to switch the Python flagd provider to use the flagd-evaluator Rust-based implementation. This is a positive step towards unifying evaluation logic and improving performance. The core logic changes in targeting.py and the new WasmInProcessResolver are well-structured. However, there are some critical issues that need to be addressed. A large number of files from a Python virtual environment (venv) have been committed, which should be removed and added to .gitignore. Additionally, tests for the old implementation were removed, but no new tests for the new Rust-based implementation were added. It's crucial to add tests to verify the correctness of the new implementation. I've also left a minor comment regarding Python best practices in the new wasm_in_process.py file.

[gemini-code-assist]

It's standard practice to place all imports at the top of the file. This improves readability and avoids re-importing the module on every call to this method during an exception. Please move import logging to the top of the file. It's also a good practice to initialize the logger as a module-level constant, for example:

# At top of file
import logging

_logger = logging.getLogger("openfeature.contrib")

And then use _logger in your except block.