[ENH] [DO NOT MERGE] Demo for #4660

[HammadB]

demo for #4660

[github-actions]

Reviewer Checklist

Please leverage this checklist to ensure your code review is thorough before approving

Testing, Bugs, Errors, Logs, Documentation

• Can you think of any use case in which the code does not behave as intended? Have they been tested?
• Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• If appropriate, are there adequate property based tests?
• If appropriate, are there adequate unit tests?
• Should any logging, debugging, tracing information be added or removed?
• Are error messages user-friendly?
• Have all documentation changes needed been made?
• Have all non-obvious changes been commented?

System Compatibility

• Are there any potential impacts on other parts of the system or backward compatibility?
• Does this change intersect with any items on our roadmap, and if so, is there a plan for fitting them together?

Quality

• Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)

[github-actions]

Please tag your PR title with one of: [ENH | BUG | DOC | TST | BLD | PERF | TYP | CLN | CHORE]. See https://docs.trychroma.com/contributing#contributing-code-and-ideas

[HammadB]

not good

[propel-code-bot]

Add Example: Extensible Metering Capability System with Trait-Based Macros in Rust

This PR introduces a comprehensive demonstration of a trait-based, macro-powered approach for extensible metering event capabilities in Rust. It includes new macro definitions for managing event capabilities, example trait and struct implementations, and an illustrative event stack mechanism. Documentation and commentary outline the design rationale, trade-offs, and usage patterns for adding new capabilities, emphasizing callsite ergonomics and extensibility. The changes are encapsulated in a new example.rs module, with supporting macro infrastructure added, and integrated into the crate.

Key Changes:
• Introduced example.rs with a demo implementation of a capability-based Metering event system using Rust traits and macros.
• Defined and exported macros: declare_event_capabilities, impl_event_capabilities, and impl_dyn_event_forwarders to facilitate extensible metering context capabilities.
• Demonstrated creation and use of traits (e.g., AddRequestStartTime, LogCacheAccess), context struct (AMeteringContext), and dynamic event stack (EventStack).
• Added test coverage in the example module to show real usage (stack push/pop, capability assignment, trait pattern usage).
• Updated library root (lib.rs) to include the example code and macro module.

Affected Areas:
• rust/metering/src/example.rs (new example code and documentation)
• rust/metering/src/macros.rs (new macros for trait extensibility)
• rust/metering/src/lib.rs (integration of new example and macros)
• rust/js_bindings/npm/darwin-arm64/package-lock.json (minor addition, likely unrelated to metering changes)

Potential Impact:

Functionality: Does not alter production metering logic, but introduces reusable patterns/macros for future capability extension. Intended as a demo-future integrations could leverage these macros to add new functionalities with reduced boilerplate.

Performance: No direct runtime impact; dynamic capability checks may add minimal cost when/if this pattern is adopted in production code.

Security: No security implications introduced.

Scalability: Pattern supports scalable addition of new context capabilities and partial implementations; boilerplate remains manageable due to macro usage.

Review Focus:
• Macro correctness, robustness, and ergonomic design for future extension.
• Clarity and extensibility of the trait pattern and macro integration.
• Validate that example code aligns with the proposed approach for modularity and future-proofing.
• Ensure that modifications to the crate root/module layout are non-invasive to existing functionality.

Testing Needed

• Run the included unit test (test_example) in example.rs to verify stack and capability behaviors.
• Test macro expansions with other traits/capabilities to confirm generic applicability and correctness.

Code Quality Assessment

rust/metering/src/example.rs: Well-commented and structured as a demonstration. Naming is intentionally generic/example-oriented, as noted by the author.

rust/metering/src/macros.rs: Clear, Rust-idiomatic macros with documentation and multiple expansion cases covered.

rust/metering/src/lib.rs: Straightforward integration; separation of example code is appropriate.

rust/js_bindings/npm/darwin-arm64/package-lock.json: No issues; appears auto-generated/minor.

Best Practices

Modularity:
• Trait-based composition
• Macro-powered extensibility
• Separation of concerns between example/demo and actual implementation

Testing:
• Inclusion of representative tests for new patterns

Documentation:
• Extensive inline commentary and guidelines
• Design rationale documented in code

Potential Issues

• Macro-generated error paths return default values or errors that could be easy to misuse (silent no-ops on missing capabilities). This risk is documented by the author.
• Trait naming and organization is currently 'example-y' and will need refinement before wider adoption.
• Actual integration with live metering infrastructure is not attempted here; migration path is not part of this demo.

This summary was automatically generated by @propel-code-bot

[HammadB]

example of what downstream callers who want to populate may do

[HammadB]

this is an example of what you'd do at the "end of the request"

[HammadB]

example, we can make it a bit nicer facade

[entelligence-ai-reviews]

Review Summary

Skipped posting 6 drafted comments based on your review threshold. Feel free to update them here.

Draft Comments

rust/metering/src/example.rs:73-76

The `MeteringContext` trait uses undefined macros `declare_event_capabilities!` in its definition. Without these macro definitions, the trait cannot be properly compiled or used.

Scores:

• Production Impact: 5
• Fix Specificity: 2
• Urgency Impact: 5
• Total Score: 12

Reason for filtering: Comment does not violate any strict rules

Analysis: Undefined macros will cause compilation failures preventing deployment, but the fix direction is vague without knowing where the macro should be defined or imported from

rust/metering/src/example.rs:84-88

The `impl_dyn_event_forwarders!` macro is called but not defined, which will prevent compilation. The macro appears to be essential for the capability forwarding mechanism.

Scores:

• Production Impact: 5
• Fix Specificity: 3
• Urgency Impact: 5
• Total Score: 13

Reason for filtering: Comment identifies a critical compilation issue that prevents the code from building

Analysis: This is a compilation-blocking issue where a required macro is undefined. Production impact is maximum since code won't compile. Fix specificity is moderate as the macro needs to be defined but implementation details aren't provided. Urgency is maximum as this prevents any deployment.

rust/metering/src/example.rs:126-128

The `impl_event_capabilities!` macro is used but not defined, preventing the `AMeteringContext` from properly implementing the capability interface required by the `MeteringContext` trait.

Scores:

• Production Impact: 5
• Fix Specificity: 3
• Urgency Impact: 5
• Total Score: 13

Reason for filtering: Comment does not violate any strict rules and meets quality threshold

Analysis: Undefined macro will cause compilation failure preventing deployment. Clear compilation error but fix requires defining the macro implementation. Critical issue that blocks system functionality completely.

rust/metering/src/lib.rs:97-97

The `action` parameter is redundantly assigned using `action: action` instead of the more idiomatic field shorthand syntax `action`. This creates unnecessary verbosity without any functional benefit.

Scores:

• Production Impact: 1
• Fix Specificity: 5
• Urgency Impact: 1
• Total Score: 7

Reason for filtering: This is a minor style improvement with no production impact, low urgency, and falls well below the required threshold of 13

Analysis: This comment addresses Rust field shorthand syntax which is purely stylistic with zero production impact or urgency. While the fix is very specific and correct, the total score of 7 is well below the required threshold of 13 for inclusion.

rust/metering/src/macros.rs:60-68

The macro generates methods that return `Result<&mut dyn $cap_trait, String>` but the error handling in `impl_dyn_event_forwarders` only uses `Err(_)` pattern matching, which discards potentially useful error information that could help with debugging capability mismatches.

Scores:

• Production Impact: 1
• Fix Specificity: 5
• Urgency Impact: 1
• Total Score: 7

Reason for filtering: This is a logging/debugging improvement suggestion rather than a critical bug fix. The current error handling works correctly by providing default values when capability access fails. Adding error logging is a nice-to-have enhancement but doesn't fix any broken functionality.

Analysis: Production impact is minimal since the code already handles errors correctly with fallback behavior. Fix is very specific with exact code provided. Urgency is very low as this is purely a debugging enhancement, not a functional fix. Total score of 7 is well below the 13 threshold.

rust/metering/src/macros.rs:65-65

The `Default::default()` fallback assumes all return types implement `Default` trait, but this constraint is not enforced in the macro signature. This will cause compilation errors when the return type doesn't implement `Default`.

Scores:

• Production Impact: 5
• Fix Specificity: 2
• Urgency Impact: 4
• Total Score: 11

Reason for filtering: Comment identifies a legitimate compilation error that will occur when macro is used with types not implementing Default trait

Analysis: High production impact as this causes compilation failures, but the suggested fix is unclear and doesn't actually solve the constraint issue. The urgency is high since it breaks builds, but total score of 11 falls below threshold of 13.

[entelligence-ai-reviews]

Walkthrough

This PR introduces foundational infrastructure for deterministic dependency management and extensible event capability handling in the Rust metering module and its JavaScript bindings. It adds platform-specific and general package-lock.json files for reproducible npm builds, and implements a trait-based, macro-driven framework for metering capabilities, including new macros and example usage. Module visibility and declarations are updated to support these features.

Changes

File(s)	Summary
rust/js_bindings/npm/darwin-arm64/package-lock.json	Added platform-specific package-lock.json for darwin-arm64 npm package to ensure deterministic dependency resolution.
rust/js_bindings/package-lock.json	Added general package-lock.json for JavaScript bindings to lock Node.js dependencies and enable reproducible builds.
rust/metering/src/example.rs	Introduced a new example.rs file with a trait-based framework for metering capabilities, example implementations, and tests.
rust/metering/src/lib.rs	Updated module declarations: added internal 'example' module, made 'macros' module public with macro-use, no logic changes.
rust/metering/src/macros.rs	Added macros.rs defining macros for event capability trait generation, implementation, and dynamic forwarding to reduce boilerplate.

Sequence Diagram

This diagram shows the interactions between components:

sequenceDiagram
    title Metering Context Capability System

    participant Client
    participant EventStack
    participant MeteringContext as "dyn MeteringContext"
    participant AMeteringContext
    participant AddRequestStartTime as "AddRequestStartTime Trait"
    participant LogCacheAccess as "LogCacheAccess Trait"
    participant AsAny as "AsAny Trait"

    Note over MeteringContext, AsAny: The system enables type-safe capabilities<br/>on metering contexts with ergonomic access

    %% Creating and pushing an event
    Client->>AMeteringContext: new("Initial data")
    AMeteringContext-->>Client: AMeteringContext instance
    Client->>Client: Box as dyn MeteringContext
    Client->>EventStack: push_event(boxed_event)
    
    %% Using capabilities through trait methods
    Client->>EventStack: peek_event()
    EventStack-->>Client: &mut Box<dyn MeteringContext>
    
    %% Using capabilities through trait methods
    Client->>MeteringContext: add_request_start_time(Instant::now())
    activate MeteringContext
    Note over MeteringContext: Capability method forwarding
    MeteringContext->>MeteringContext: as_add_request_start_time()
    MeteringContext->>AddRequestStartTime: add_request_start_time()
    AddRequestStartTime->>AMeteringContext: add_request_start_time()
    AMeteringContext->>AMeteringContext: self.request_start_time = Some(start_time)
    deactivate MeteringContext
    
    %% Calling an unsupported capability (no-op)
    Client->>MeteringContext: cache_hit()
    activate MeteringContext
    Note over MeteringContext: Method exists but no implementation<br/>for AMeteringContext (no-op)
    MeteringContext->>MeteringContext: as_log_cache_access()
    MeteringContext-->>Client: (no-op, returns silently)
    deactivate MeteringContext
    
    %% Finalizing the event
    Client->>EventStack: finalize_event::<AMeteringContext>()
    activate EventStack
    EventStack->>EventStack: events.pop()
    EventStack->>AsAny: as_any_box()
    AsAny->>AsAny: downcast::<AMeteringContext>()
    
    alt Successful downcast
        AsAny-->>EventStack: Ok(*target_event)
        EventStack-->>Client: Ok(AMeteringContext)
    else Type mismatch
        AsAny-->>EventStack: Err
        EventStack-->>Client: Err("Event type mismatch")
    else No event
        EventStack-->>Client: Err("No event to finalize")
    end
    deactivate EventStack
    
    Note over Client, AsAny: The capability system allows strongly-typed<br/>access to capabilities without knowing<br/>concrete types at the call site

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[entelligence-ai-reviews]

Correctness: The declare_event_capabilities!, impl_dyn_event_forwarders!, and impl_event_capabilities! macros are used but not defined anywhere in the codebase. This will cause compilation failures when the code is built.

[entelligence-ai-reviews]

Correctness: The AMeteringContext struct does not implement the MeteringContext trait, but the code expects it to be usable as Box<dyn MeteringContext>. This will cause a trait bound error during compilation.

[entelligence-ai-reviews]

Correctness: The test calls cache_hit() method on a MeteringContext that doesn't implement LogCacheAccess trait. This will result in a method not found compilation error since AMeteringContext only implements AddRequestStartTime.