@minux There have been several occasions where I have had to implement marshaller methods to filter out fields depending on where the data is going. For example, in my models in an MVC application I sometimes like certain attributes to not be Marshalled, say a foreign key for an embedded type, back to the client and only allow it to be Unmarshalled from a request to set and perform business logic on.

As I said, I do this already with the MarshalJSON/UnmarshalJSON, though it seems redundant when there already exists a similar functionality for omitempty.

Yeah, as @minux suggested, it's probably better to just use two structs. As of Go 1.8 this is now easier. See https://beta.golang.org/doc/go1.8#language

I'm going to decline this proposal, because the json package is pretty locked down at this point and it seems like there's already a solution. Even if the solution might not be ideal for you, it's probably better than complicating the json package for everybody else.

@bradfitz What's the reasoning behind the omit ´json:"-"´option as that seems essentially the same. I could just create a struct that doesn't contain that field, but its cleaner and less copying to add the tag.