[duplicate-code] Duplicate Code Detected: Parallel MCP server implementations

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🔍 Duplicate Code Detected: Parallel MCP server implementations

Analysis of commit 8d26b38

Assignee: @copilot

Summary

Two separate MCP server implementations exist in the JavaScript runtime: mcp_server.cjs and mcp_server_core.cjs. Both register tools and handle JSON-RPC requests but differ in data structures, logging, and validation, increasing the risk of divergent behavior across transports (HTTP vs stdio) and duplicated maintenance.

Duplication Details

Pattern: Duplicate MCP server cores for tool registration/JSON-RPC

• Severity: Medium
• Occurrences: 2 implementations
• Locations:
  • pkg/workflow/js/mcp_server.cjs (lines 23-186)
  • pkg/workflow/js/mcp_server_core.cjs (lines 458-575)
• Code Sample:

  // mcp_server.cjs: tool registration and handler dispatch
  tool(name, description, inputSchema, handler) { this.tools.set(name, { name, description, inputSchema, handler }); }
  async handleRequest({ id, method, params }) { /* initialize, tools/list, tools/call, ping */ }
  
  // mcp_server_core.cjs: duplicated registration and dispatch
  function registerTool(server, tool) { server.tools[normalizeTool(tool.name)] = { ...tool }; }
  async function handleMessage(server, req) { /* initialize, tools/list, tools/call */ }

Impact Analysis

• Maintainability: Two code paths to keep in sync for MCP behavior and validation; fixes may land in one server but not the other.
• Bug Risk: Divergent capabilities (e.g., error handling, schema validation) can yield different outcomes between HTTP and stdio transports, complicating debugging.
• Code Bloat: Extra server core inflates surface area and documentation burden.

Refactoring Recommendations

1. Unify MCP server core

   • Extract a single shared server implementation (e.g., reuse mcp_server_core for both HTTP and stdio) and make MCPServer a thin adapter around it.
   • Estimated effort: 4-6 hours (API alignment, tests).
   • Benefits: Single source of truth for JSON-RPC behavior and validation.

2. Share validation and tool registration utilities

   • Export common functions (normalize/register/handle) and have transports depend on them instead of bespoke logic.
   • Estimated effort: 2-3 hours.
   • Benefits: Eliminates drift between transports and simplifies future fixes.

Implementation Checklist

• Review duplication findings
• Prioritize refactoring tasks
• Create refactoring plan
• Implement changes
• Update tests
• Verify no functionality broken

Analysis Metadata

• Analyzed Files: 4
• Detection Method: Serena semantic code analysis
• Commit: 8d26b38
• Analysis Date: 2025-12-07 21:05:05Z

AI generated by Duplicate Code Detector