Make frame processors stateless

[leynos]

Summary

• define a SendError preserving encode and write failures
• change FrameProcessor trait to use synchronous, immutable methods
• update WireframeApp::send_response to use &self and return SendError
• extend response tests for encode and IO errors
• switch to trait-based serialization using Serializer and BincodeSerializer
• remove unnecessary default() calls in examples and tests
• document response serialization tests module

Testing

• cargo clippy -- -D warnings
• RUSTFLAGS="-D warnings" cargo test
• markdownlint docs/preamble-validator.md docs/roadmap.md docs/rust-binary-router-library-design.md docs/rust-testing-with-rstest-fixtures.md README.md
• nixie docs/preamble-validator.md docs/roadmap.md docs/rust-binary-router-library-design.md docs/rust-testing-with-rstest-fixtures.md README.md

---

https://chatgpt.com/codex/tasks/task_e_6850a3439ea8832287c8431cdfbb87f9

Summary by Sourcery

Make frame processors stateless by refactoring the FrameProcessor trait to synchronous immutable methods, introduce SendError for improved error handling, switch to a trait-based serialization model, and bolster tests and documentation for response serialization.

New Features:

• Introduce SendError type to capture both encoding and write failures
• Adopt trait-based serialization with a Serializer trait and BincodeSerializer implementation

Enhancements:

• Refactor FrameProcessor trait to use synchronous, immutable methods
• Update WireframeApp::send_response to take &self and return SendError

Documentation:

• Document the response serialization tests module

Tests:

• Extend response tests to cover encoding and I/O errors

Chores:

• Remove unnecessary default() calls in examples and tests

Summary by CodeRabbit

• New Features

  • Introduced configurable serialisation and framing support, allowing custom serialisers and frame processors.
  • Added a default length-prefixed framing strategy and bincode serialiser.
  • Exposed serialiser configuration directly in the application builder.

• Bug Fixes

  • Improved error handling for response encoding and transmission failures.

• Documentation

  • Updated and clarified example code and documentation to reflect new configuration options and usage.
  • Added a new section explaining response serialisation and framing mechanisms.

• Tests

  • Added comprehensive tests for response serialisation, framing, and error scenarios.

[sourcery-ai]

Reviewer's Guide

This PR refactors framing and serialization to be fully stateless and synchronous, introduces a pluggable Serializer API with a default BincodeSerializer, overhauls WireframeApp::send_response to return a detailed SendError, and updates tests, examples, and documentation to reflect these changes.

File-Level Changes

Change	Details	Files
Introduce trait-based serialization with a default Bincode serializer	Define new Serializer trait for encoding messages Implement BincodeSerializer as the default serializer Replace ad-hoc serialization logic with the new Serializer API	src/serializer.rs src/app.rs
Refactor FrameProcessor to be stateless and synchronous	Change FrameProcessor methods to take &self and return synchronously Provide a new LengthPrefixedProcessor implementation Update application builder to accept a custom frame processor	src/frame_processor.rs src/app_builder.rs
Overhaul response handling to return detailed send errors	Add SendError type capturing encode and I/O failures Change WireframeApp::send_response to use &self and return Result<_, SendError> WireframeApp builder now accepts custom serializer and frame processor	src/error.rs src/app.rs
Extend tests and documentation for serialization and error cases	Add tests covering encoding failures and I/O error propagation Document the response serialization and framing tests module Update README and design docs to describe the new APIs	tests/response.rs docs/preamble-validator.md docs/roadmap.md docs/rust-binary-router-library-design.md docs/rust-testing-with-rstest-fixtures.md README.md
Cleanup redundant default() calls in examples and tests	Remove unnecessary default() invocations from examples Strip default() calls in test setups	examples/* tests/*

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Walkthrough

This update introduces a generic Serializer trait and a default BincodeSerializer implementation, enabling custom serialisation strategies in the framework. The WireframeApp struct is now generic over the serializer and allows configuration of both serialisation and framing. Synchronous, stateless frame processing is implemented, and comprehensive response serialisation and error handling are added. Documentation and tests are updated accordingly.

Changes

File(s)	Change Summary
src/serializer.rs	New module introducing the Serializer trait and BincodeSerializer implementation for serialising/deserialising messages with error handling.
src/app.rs	Refactored WireframeApp to be generic over serializer; added fields for serializer and frame processor; implemented builder methods for configuration; introduced SendError enum and send_response method for serialising and sending responses; updated trait bounds and method signatures.
src/frame.rs	Refactored FrameProcessor trait to use synchronous, immutable methods; removed async dependencies; added LengthPrefixedProcessor for big-endian length-prefixed framing.
src/lib.rs	Added public serializer module; re-exported BincodeSerializer and Serializer at the crate root.
tests/response.rs	New test module verifying response serialisation, framing, error propagation, and handling of incomplete frames and write failures using custom test types and a failing writer.
README.md, docs/roadmap.md, docs/rust-binary-router-library-design.md	Updated documentation and examples to reflect new serializer API, clarify usage, describe response serialisation and framing, and mark roadmap item as complete. Improved formatting and code block consistency.

Sequence Diagram(s)

sequenceDiagram
    participant App as WireframeApp
    participant Handler as Handler
    participant Serializer as Serializer
    participant FrameProc as FrameProcessor
    participant Stream as AsyncWrite

    Handler->>App: Returns response (implements Responder)
    App->>Serializer: serialize(response)
    Serializer-->>App: Serialised bytes
    App->>FrameProc: encode(bytes)
    FrameProc-->>App: Framed bytes
    App->>Stream: write(framed bytes)
    Stream-->>App: Write result (Ok or Error)

Loading

Possibly related PRs

• leynos/wireframe#44: Updates the Message trait and decoding bounds to use bincode::BorrowDecode, conceptually related as both PRs address serialisation/deserialisation traits.
• leynos/wireframe#8: Introduced the original async FrameProcessor trait, which is now refactored in this PR to use synchronous methods.

Poem

In bytes and frames we rabbits play,
With serializers leading the way.
Bincode or custom, choose your delight,
Length-prefixed framing keeps packets tight.
Errors are handled, responses are sent,
Our wireframe dreams are now content!
🐇✨

✨ Finishing Touches

🧪 Generate Unit Tests

• Create PR with Unit Tests
• Post Copyable Unit Tests in Comment
• Commit Unit Tests in branch l7tg5u-codex/add-response-serialization-and-transmission

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