Disadvantages of config injection

As we have seen, config injection can be used with both constructors and functions, It is, therefore, possible to build a system with only config injection. Unfortunately, config injection does have some disadvantages.

Passing config instead of abstract dependencies leaks implementation details—Consider the following code:

type PeopleFilterConfig interface {
   DSN() string
}

func PeopleFilter(cfg PeopleFilterConfig, filter string) ([]Person, error) {
   // load people
   loader := &PersonLoader{}
   people, err := loader.LoadAll(cfg)
   if err != nil {
      return nil, err
   }

   // filter people
   out := []Person{}
   for _, person := range people {
      if strings.Contains(person.Name, filter) {
         out = append(out, person)
      }
   }

   return out, nil
}

type PersonLoaderConfig interface {
   DSN() string
}

type PersonLoader struct{}

func...