func handlerTakesContext()

in lambda/handler.go [158:187]
27 lines of code
11 McCabe index (conditional complexity)

func handlerTakesContext(handler reflect.Type) (bool, error) {
	switch handler.NumIn() {
	case 0:
		return false, nil
	case 1:
		contextType := reflect.TypeOf((*context.Context)(nil)).Elem()
		argumentType := handler.In(0)
		if argumentType.Kind() != reflect.Interface {
			return false, nil
		}

		// handlers like func(event any) are valid.
		if argumentType.NumMethod() == 0 {
			return false, nil
		}

		if !contextType.Implements(argumentType) || !argumentType.Implements(contextType) {
			return false, fmt.Errorf("handler takes an interface, but it is not context.Context: %q", argumentType.Name())
		}
		return true, nil
	case 2:
		contextType := reflect.TypeOf((*context.Context)(nil)).Elem()
		argumentType := handler.In(0)
		if argumentType.Kind() != reflect.Interface || !contextType.Implements(argumentType) || !argumentType.Implements(contextType) {
			return false, fmt.Errorf("handler takes two arguments, but the first is not Context. got %s", argumentType.Kind())
		}
		return true, nil
	}
	return false, fmt.Errorf("handlers may not take more than two arguments, but handler takes %d", handler.NumIn())
}