golint-sl

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errorwrap

About 355 wordsAbout 1 min

2025-01-16

Detects bare error returns that lose context.

Category

Error Handling

What It Checks

This analyzer finds error returns that don't add context, making debugging difficult.

Why It Matters

Bare error returns lose the call chain:

Error: connection refused

With context, you can trace the error:

Error: get user "alice": fetch from database: connection refused

Examples

Bad

func ProcessOrder(orderID string) error {
    order, err := db.GetOrder(orderID)
    if err != nil {
        return err  // Lost context: what were we doing?
    }

    if err := validateOrder(order); err != nil {
        return err  // Lost context: which order failed?
    }

    return nil
}
func ProcessOrder(orderID string) humane.Error {
    order, err := db.GetOrder(orderID)
    if err != nil {
        return humane.Wrap(err, "failed to get order",
            "verify order ID exists in the database",
            "check database connectivity")
    }

    if err := validateOrder(order); err != nil {
        return humane.Wrap(err, "order validation failed",
            "review the order details for required fields")
    }

    return nil
}

Good: Using fmt.Errorf

func ProcessOrder(orderID string) error {
    order, err := db.GetOrder(orderID)
    if err != nil {
        return fmt.Errorf("get order %s: %w", orderID, err)
    }

    if err := validateOrder(order); err != nil {
        return fmt.Errorf("validate order %s: %w", orderID, err)
    }

    return nil
}

Prefer humane.Wrap()

When possible, use humane.Wrap() instead of fmt.Errorf():

  • Provides actionable advice to users
  • Creates structured error messages
  • Enables better error presentation in CLIs

The %w Verb

If using fmt.Errorf, use %w (not %v or %s) to wrap errors:

// Good: preserves error chain for errors.Is/As
return fmt.Errorf("context: %w", err)

// Bad: breaks error chain
return fmt.Errorf("context: %v", err)

Exceptions

The analyzer allows bare returns in certain cases:

// Allowed: returning sentinel errors
if notFound {
    return ErrNotFound  // Sentinel error, context not needed
}

// Allowed: simple getters that add no context
func (s *Service) Client() *http.Client {
    return s.client
}

Configuration

# .golint-sl.yaml
analyzers:
  errorwrap: true  # enabled by default

When to Disable

  • Very simple functions where context is obvious
  • Performance-critical paths (wrapping has overhead)
analyzers:
  errorwrap: false

See Also