90 lines
2.8 KiB
Markdown
90 lines
2.8 KiB
Markdown
# Go Anti-Patterns (Auto-Fail)
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> **Load this file** during code reviews of Go code. Patterns listed here are **immediate findings** — no judgment needed. If the pattern exists, it is a finding.
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---
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## Auto-Fail Table
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| Pattern | Severity | Tag | Correct Fix |
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|---|---|---|---|
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| `defer X.Close()` (bare) | Critical | `[RES]` | Error-checked closure with `slog.Warn` |
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| `//nolint:errcheck` | Critical | `[ERR]` | Handle the error — use error-checked closure |
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| `defer tx.Rollback()` (bare) | Critical | `[RES]` | Error-checked closure with `sql.ErrTxDone` guard |
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| `fmt.Printf` / `fmt.Println` | Major | `[OBS]` | Replace with `slog` structured logging |
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| `log.Printf` / `log.Println` | Major | `[OBS]` | Replace with `slog` structured logging |
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| `resp.Body.Close()` without drain | Major | `[RES]` | `io.Copy(io.Discard, resp.Body)` then close |
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| Empty `if err != nil {}` block | Critical | `[ERR]` | Handle, return, or log the error |
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| `_ = someFunc()` (discarded error) | Major | `[ERR]` | Handle the error explicitly |
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---
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## Detection Commands
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Use these grep patterns to scan for anti-patterns before manual review:
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```bash
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# Bare defer Close/Rollback (no error check)
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grep -rn 'defer.*\.Close()' --include='*.go'
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grep -rn 'defer.*\.Rollback()' --include='*.go'
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# nolint:errcheck suppression
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grep -rn 'nolint:errcheck' --include='*.go'
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# Unstructured logging in production code
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grep -rn 'fmt\.Printf\|fmt\.Println\|log\.Printf\|log\.Println' --include='*.go' | grep -v '_test.go'
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# Discarded errors
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grep -rn '_ = ' --include='*.go' | grep -v '_test.go'
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```
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---
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## Correct Patterns (Reference)
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### Resource Cleanup
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```go
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// ✅ Rows / Statements / Connections
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defer func() {
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if err := rows.Close(); err != nil {
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slog.Warn("failed to close rows", "error", err, "operation", "<operation>")
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}
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}()
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// ✅ Transaction Rollback
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defer func() {
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if err := tx.Rollback(); err != nil && !errors.Is(err, sql.ErrTxDone) {
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slog.Error("failed to rollback transaction", "error", err, "operation", "<operation>")
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}
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}()
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// ✅ HTTP Response Body
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defer func() {
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if _, err := io.Copy(io.Discard, resp.Body); err != nil {
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slog.Warn("failed to drain response body", "error", err)
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}
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if err := resp.Body.Close(); err != nil {
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slog.Warn("failed to close response body", "error", err)
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}
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}()
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```
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### Structured Logging
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```go
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// ❌ fmt.Printf("User %s logged in from %s\n", userID, ip)
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// ❌ log.Printf("User %s logged in from %s", userID, ip)
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// ✅
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slog.Info("user login", "userId", userID, "ip", ip)
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```
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---
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## References
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- Go Idioms and Patterns @go-idioms-and-patterns.md
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- Logging and Observability Principles @logging-and-observability-principles.md
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- Error Handling Principles @error-handling-principles.md
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- Resources and Memory Management Principles @resources-and-memory-management-principles.md
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