[duplicate-code] Duplicate Code Pattern: Upstream Forwarding and Response Reading in proxy/handler.go

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Part of duplicate code analysis: #2300

Summary

The block that forwards a request to the upstream GitHub API and reads the response body — including identical error messages — appears twice in internal/proxy/handler.go (handleWithDIFC and passthrough).

Duplication Details

Pattern: forwardToGitHub → io.ReadAll → error handling

• Severity: Low

• Occurrences: 2 instances in the same file

• Locations:

  • internal/proxy/handler.go (lines 148–165) — inside handleWithDIFC
  • internal/proxy/handler.go (lines 279–291) — inside passthrough

• Code Sample (both instances are structurally identical):

  resp, err := s.forwardToGitHub(ctx, method, path, body, contentType, clientAuth)
  if err != nil {
      http.Error(w, "upstream request failed", http.StatusBadGateway)
      return
  }
  defer resp.Body.Close()
  
  respBody, err := io.ReadAll(resp.Body)
  if err != nil {
      http.Error(w, "failed to read upstream response", http.StatusBadGateway)
      return
  }

  Even the error strings ("upstream request failed", "failed to read upstream response") are identical between the two sites.

Impact Analysis

• Maintainability: If error handling needs to change (e.g., logging, status code), both sites must be updated.
• Bug Risk: The error messages are already identical; a future edit to one site might silently diverge.
• Code Bloat: ~10 lines that could be 1–2 lines each via a shared helper.

Refactoring Recommendations

1. Extract a forwardAndReadBody helper
   • Add to internal/proxy/handler.go (or http_helpers.go from Pattern 1):

     // forwardAndReadBody forwards the request to GitHub and returns the raw response body.
     // On error it writes an appropriate HTTP error to w and returns nil, nil.
     func (h *proxyHandler) forwardAndReadBody(
         w http.ResponseWriter,
         ctx context.Context,
         method, path string,
         body io.Reader,
         contentType, clientAuth string,
     ) (*http.Response, []byte) {
         resp, err := h.server.forwardToGitHub(ctx, method, path, body, contentType, clientAuth)
         if err != nil {
             http.Error(w, "upstream request failed", http.StatusBadGateway)
             return nil, nil
         }
         respBody, err := io.ReadAll(resp.Body)
         resp.Body.Close()
         if err != nil {
             http.Error(w, "failed to read upstream response", http.StatusBadGateway)
             return nil, nil
         }
         return resp, respBody
     }

   • Replace both blocks with calls to forwardAndReadBody.
   • Estimated effort: ~1 hour (including test validation)
   • Benefits: single error-message source of truth; easier to add logging/tracing later

Implementation Checklist

• Review both duplicated forwarding blocks in internal/proxy/handler.go
• Extract forwardAndReadBody helper method
• Replace both inline blocks with helper calls
• Verify tests still pass (make test)
• Confirm no functionality broken

Parent Issue

See parent analysis report: #2300
Related to #2300

Generated by Duplicate Code Detector · ◷

• expires on Mar 29, 2026, 3:03 AM UTC