Always send lowlevel_error response to client (#2731)

[MitchLewis930]

PR_052

[greptile-apps]

Greptile Overview

Greptile Summary

Refactored error response handling to ensure lowlevel_error responses are always sent to clients

• Extracted write_response method from handle_request to enable reuse in error paths
• Modified client_error in lib/puma/server.rb to call lowlevel_error + write_response instead of client.write_error
• Ensured custom error handlers return normalized Rack tuples [status || default_status, headers || {}, body || []]
• Fixed indentation for chunked transfer encoding code
• Added nil-safety check client.body.close if client.body in cleanup
• Updated tests to verify custom error handler responses are sent correctly

Confidence Score: 5/5

• Safe to merge - well-tested refactoring that improves error handling consistency
• Code follows existing patterns, adds proper test coverage, and fixes a bug where custom error handlers weren't being sent to clients. The refactoring reduces code duplication and improves maintainability.
• No files require special attention

Important Files Changed

Filename	Overview
lib/puma/request.rb	Extracted write_response method to enable reuse in error handling paths; simplified request flow by removing nested begin blocks
lib/puma/server.rb	Modified client_error to send proper error responses via lowlevel_error + write_response; ensured handler return values are normalized to proper Rack tuple format

Sequence Diagram

sequenceDiagram
    participant Client
    participant Server
    participant Request
    participant App
    
    Client->>Server: HTTP Request
    Server->>Server: process_client()
    Server->>Request: handle_request()
    
    alt Normal Flow
        Request->>App: @app.call(env)
        App-->>Request: [status, headers, body]
        Request->>Request: write_response()
        Request->>Client: HTTP Response
    else ThreadPool::ForceShutdown
        Request->>Request: lowlevel_error(503)
        Request->>Request: write_response()
        Request->>Client: 503 Error Response
    else Exception in App
        Request->>Request: lowlevel_error(500)
        Request->>Request: write_response()
        Request->>Client: 500 Error Response
    else Client I/O Error (HttpParserError)
        Server->>Server: client_error()
        Server->>Server: lowlevel_error(400)
        Server->>Request: write_response()
        Request->>Client: 400 Error Response
    else Client I/O Error (Other)
        Server->>Server: client_error()
        Server->>Server: lowlevel_error(500)
        Server->>Request: write_response()
        Request->>Client: 500 Error Response
    end

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