fix!: flagd, behavioral tests conformance (evaluation and config)

[erenatas]

This PR

This change may be breaking to existing users

If both FLAGD_OFFLINE_FLAG_SOURCE_PATH and FLAGD_RESOLVER were set, FLAGD_OFFLINE_FLAG_SOURCE_PATH overrode the resolver type to File, ignoring FLAGD_RESOLVER.
What is done now:
FLAGD_RESOLVER takes precedence. If set, it is respected and FLAGD_OFFLINE_FLAG_SOURCE_PATH does not override the resolver type to File.

Add evaluation behavioral tests as well, did not require any change in implementation except error mapping with expectation

Related Issues

Improves #43

Notes

Follow-up Tasks

How to test

[gemini-code-assist]

Summary of Changes

Hello @erenatas, 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 modernizes the project by updating to the Rust 2024 edition and bringing various dependencies to their latest versions. It introduces significant enhancements to the flagd provider, focusing on improved cache management and a more robust targeting evaluation system through an updated integration with datalogic-rs. The env-var provider also benefits from refined testing practices, ensuring greater stability and reliability across the board.

Highlights

• Rust Edition and Dependency Updates: The project has been updated to Rust 2024 edition across multiple crates (main, env-var, flagd, flipt), along with a bump in the minimum supported Rust version (MSRV) for flagd. Numerous dependencies, including open-feature, async-trait, tokio, tonic, prost, datalogic-rs, and various testing utilities, have been upgraded to their latest versions.
• Enhanced env-var Provider Testing: The env-var provider's example code and Cucumber tests have been refactored to use temp-env and test-with::runner! for safer and more isolated environment variable handling, preventing test pollution and ensuring reliable test execution.
• flagd Provider Cache Management: The flagd provider's cache service now includes a purge method, and both FileResolver and InProcessResolver have been updated to clear their caches automatically when flag store updates are detected, ensuring data freshness.
• Improved flagd Targeting Logic: The flagd provider's in-process targeting logic has been significantly refactored to integrate with the updated datalogic-rs library's Operator trait. This change modernizes the fractional and semver targeting implementations, improving context handling and evaluation.
• Code Modernization and Test Reliability: The codebase now utilizes newer Rust syntax like if let Some(...) && let Some(...) for cleaner optional value unwrapping. Additionally, retry mechanism tests in flagd have been made more robust by using dynamic ports, and environment variable handling in gherkin_config_test.rs has been improved for better test isolation.

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[gemini-code-assist]

Code Review

This pull request introduces a number of significant improvements and fixes across the flagd and env-var crates. Key changes include upgrading to the Rust 2024 edition, updating numerous dependencies, and most notably, a major refactoring of the in-process targeting engine to use datalogic-rs v4. This refactoring has greatly improved the code's safety and clarity, especially in the fractional and semver targeting operators.

The behavioral tests have also been substantially improved for better conformance and reliability. The use of test-with and temp-env to manage environment variables in tests is a great change that addresses potential flakiness from parallel test execution.

I have one suggestion in crates/flagd/src/resolver/in_process/resolver/grpc.rs to improve code consistency in cache handling, bringing it in line with the FileResolver. Overall, this is a high-quality pull request with excellent changes.

[aepfli]

should we also add a check here that source_configuration needs to be set, if the ResolverType is file?

[erenatas]

Thank you very much! I updated it.

[aepfli]

i am not sure i can really provide a review - i have no clue about rust, i just saw that this behaviour was missing, but i can give it a shot

[beeme1mr]

I'm in the same boat as @aepfli. I don't know Rust well enough to be confident in my review but the change is relatively straightforward and looks okay to me.