Are there any Go libraries which can tidy up Json output before it is sent to users?
We could unmarshall into a struct and do this manually, but we would like to know if there are any libraries which can make it easier to extract keys into the struct, which we could Marshall and send to the user?
The short answer is not really, due to the way Go handles JSON marshalling and un-marshalling. The common pattern for dealing with your use case is just to define a Response struct.
A classic example would be something like the following:
type User struct {
// fields
}
// Response type used when the user is asking about their own fields
type PrivateUserResponse struct {
// fields with struct tags
}
func (u *User) ToPrivateUserResponse() *PrivateUserResponse { ... }
// Response type used when the user is being listed in a public directory
type PublicUserResponse struct {
// fields with struct tags
}
func (u *User) ToPublicUserResponse() *PublicUserResponse { ... }
Because JSON key configuration is handled by struct tags, a library would be ill-suited to handle the unique business logic cases that arise in dealing with this problem. You might be able to find a code generator that solves this in a more generic way, but I'd recommend just writing the structs yourself - Go favors explicit and clear behavior.