[duplicate-code] Duplicate Code Pattern: Repeated forwardToGitHub + read-body sequence in proxy handler

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Part of duplicate code analysis: #2628

Summary

internal/proxy/handler.go repeats the same "call forwardToGitHub, check error, defer close, io.ReadAll body, check error" sequence at 3 separate locations — in ServeHTTP (GraphQL introspection passthrough), handleWithDIFC (Phase 3 upstream forward), and passthrough.

Duplication Details

Pattern: forwardToGitHub + defer close + io.ReadAll body

• Severity: Medium
• Occurrences: 3 sites in one file
• Locations:
  • internal/proxy/handler.go (lines 83–90) — GraphQL introspection passthrough
  • internal/proxy/handler.go (lines 173–189) — DIFC Phase 3 upstream forward
  • internal/proxy/handler.go (lines 332–343) — write passthrough
• Code Sample:

  // Site 1 (lines 83-90, slightly abbreviated):
  resp, err := h.server.forwardToGitHub(r.Context(), http.MethodPost, "/graphql", bytes.NewReader(graphQLBody), "application/json", clientAuth)
  if err != nil {
      http.Error(w, "upstream request failed", http.StatusBadGateway)
      return
  }
  defer resp.Body.Close()
  respBody, _ := io.ReadAll(resp.Body)
  
  // Site 2 (lines 177-189):
  if err != nil {
      logHandler.Printf("[DIFC] Phase 3 failed: %v", err)
      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
  }
  
  // Site 3 (lines 332-343): identical to site 2 without DIFC log line
  resp, err := h.server.forwardToGitHub(r.Context(), r.Method, path, body, ...)
  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
  }

Impact Analysis

• Maintainability: Three independent copies of the same 8-line sequence. A future change (e.g., adding a timeout, changing the error message, adding tracing) must be applied in all three places.
• Bug Risk: Site 1 silently ignores io.ReadAll errors (respBody, _ := io.ReadAll) while Sites 2 and 3 handle them — inconsistent behavior that could hide upstream body truncation.
• Code Bloat: ~24 lines that could be replaced by a helper + 3 call sites.

Refactoring Recommendations

1. Extract a forwardAndReadBody helper method on proxyHandler:

   // forwardAndReadBody forwards a request to the upstream GitHub API and reads the
   // entire response body. It writes a 502 error to w and returns nil, nil on failure.
   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
       }
       defer resp.Body.Close()
       respBody, err := io.ReadAll(resp.Body)
       if err != nil {
           http.Error(w, "failed to read upstream response", http.StatusBadGateway)
           return nil, nil
       }
       return resp, respBody
   }

   Then callers check if resp == nil { return }.

2. Fix the silent error discard at line 89 (respBody, _ := io.ReadAll(...)) to be consistent with the other sites.

   Estimated effort: ~45 min
   Benefits: consistent error handling, single place for tracing/timeout logic, fixes inconsistency bug at line 89.

Implementation Checklist

• Add forwardAndReadBody helper to proxyHandler
• Replace three inline forward+read sequences with calls to the helper
• Fix silent io.ReadAll error at line 89
• Run make agent-finished to verify no regressions

Parent Issue

See parent analysis report: #2628
Related to #2628

Generated by Duplicate Code Detector · ◷

• expires on Apr 3, 2026, 3:34 AM UTC