golint-sl

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nestingdepth

About 229 words

Enforces shallow nesting with early returns.

Category

Safety

What It Checks

This analyzer detects deeply nested code that should use early returns instead.

Why It Matters

Deep nesting is hard to read and reason about:

func Process(x int) error {
    if x > 0 {
        if x < 100 {
            if isValid(x) {
                if hasPermission() {
                    return doWork(x)  // Where am I?
                }
            }
        }
    }
    return nil
}

Examples

Bad: Deep Nesting

func Process(user *User) error {
    if user != nil {
        if user.Active {
            if user.HasPermission("write") {
                if user.Quota > 0 {
                    return performAction(user)
                } else {
                    return ErrQuotaExceeded
                }
            } else {
                return ErrNoPermission
            }
        } else {
            return ErrUserInactive
        }
    } else {
        return ErrNilUser
    }
}

Good: Early Returns

func Process(user *User) error {
    if user == nil {
        return ErrNilUser
    }
    if !user.Active {
        return ErrUserInactive
    }
    if !user.HasPermission("write") {
        return ErrNoPermission
    }
    if user.Quota <= 0 {
        return ErrQuotaExceeded
    }
    return performAction(user)
}

The Pattern

  1. Check error conditions first
  2. Return early on failure
  3. Happy path flows straight down
func Process(input Input) (Output, error) {
    // Validation - early returns
    if input.A == "" {
        return Output{}, errors.New("A is required")
    }
    if input.B < 0 {
        return Output{}, errors.New("B must be positive")
    }

    // Happy path - no nesting
    result := compute(input.A, input.B)
    return Output{Value: result}, nil
}

Configuration

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

When to Disable

  • Complex algorithms where nesting is unavoidable
  • Generated code
analyzers:
  nestingdepth: false