golint-sl

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nilcheck

About 237 wordsLess than 1 minute

2025-01-16

Enforces nil checks on pointer parameters before use.

Category

Safety

What It Checks

This analyzer detects pointer parameters that are used without being checked for nil first.

Why It Matters

Nil pointer dereferences cause panics:

panic: runtime error: invalid memory address or nil pointer dereference

Explicit nil checks provide better error messages and prevent crashes.

Examples

Bad

func ProcessUser(user *User) error {
    // Panics if user is nil!
    return user.Save()
}

Good

func ProcessUser(user *User) error {
    if user == nil {
        return errors.New("user cannot be nil")
    }
    return user.Save()
}

Bad: Multiple Usages

func UpdateProfile(user *User, profile *Profile) error {
    user.Name = profile.Name      // Both could panic!
    user.Email = profile.Email
    return user.Save()
}

Good: Check All Pointers

func UpdateProfile(user *User, profile *Profile) error {
    if user == nil {
        return errors.New("user cannot be nil")
    }
    if profile == nil {
        return errors.New("profile cannot be nil")
    }
    user.Name = profile.Name
    user.Email = profile.Email
    return user.Save()
}

Trusted Types

The analyzer skips certain types that are guaranteed non-nil by their frameworks:

  • *testing.T, *testing.B, *testing.M
  • *gin.Context, *gin.Engine
  • *cobra.Command
  • *http.Request, http.ResponseWriter
  • context.Context

Skipped Files

The analyzer skips generated files:

  • *_gen.go
  • *.pb.go
  • zz_generated*.go
  • Files in mock_* directories

Configuration

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

When to Disable

This analyzer should rarely be disabled. Nil checks are fundamental safety.

analyzers:
  nilcheck: false  # Not recommended