feat: Add legacy-states-v0 Cargo feature for backward compatibility #1076

[skalwaghe-56]

Description

This PR implements the legacy-states-v0 Cargo feature to guard backward compatibility code in the Rust codebase, as requested in issue #1076.

Changes Made

Cargo.toml

• Added legacy-states-v0 feature flag, enabled by default
• Feature is currently enabled to maintain backward compatibility

Source Code Changes

• src/setup/states.rs: Guarded the deprecated key_schema field with #[cfg(feature="legacy-states-v0")]
• src/builder/exec_ctx.rs: Updated backward compatibility logic to conditionally compile based on the feature flag

CI/CD Changes

• .github/workflows/_test.yml: Added cargo test --no-default-features --verbose to ensure both code paths compile and test successfully

Implementation Details

The feature flag approach allows for:

• Current state: Legacy compatibility code is included by default
• Future state: When CocoIndex reaches v1.0, the default can be changed to default = [] and legacy code removed
• Testing: Both configurations are tested in CI to ensure stability

Testing

• ✅ All existing tests pass with default features (128 tests)
• ✅ All tests pass with --no-default-features (128 tests)
• ✅ Pre-commit checks pass (formatting, linting, type checking)
• ✅ CI workflow includes testing for both feature configurations

Future Usage

This establishes a framework for managing backward compatibility. Additional legacy code can be guarded with the same feature flag pattern:

#[cfg(feature = "legacy-states-v0")]
// legacy code here

When ready to drop v0.x compatibility:

1. Change default = [] in Cargo.toml
2. Test thoroughly
3. Remove the feature flag and guarded code

Closes #1076.

[badmonster0]

thanks @skalwaghe-56 please revert the format changes and keep the diff minimum. due to the large volume of PRs it makes it easier for contributors to merge changes.

[skalwaghe-56]

@badmonster0 Sure, I'll do it right away!

[skalwaghe-56]

@badmonster0 Can you please review it now?

[georgeh0]

@skalwaghe-56 Thanks for this PR! Mostly looks good except a minor comment on the workflow.

[skalwaghe-56]

@georgeh0 Please check it now. Thanks!

[georgeh0]

Thanks for the PR!