Golang | Prevent empty values in Marshaled JSON

[atc0005]

From the documentation:

The "omitempty" option specifies that the field should be omitted from the encoding if the field has an empty value, defined as false, 0, a nil pointer, a nil interface value, and any empty array, slice, map, or string.

For some fields, even when omitempty is specified the resulting JSON will still contain empty fields.

Examples:

• proposal: encoding/json, encoding/xml: support zero values of structs with omitempty golang/go#11939
• DecorationConfig: add pointers to Durations. kubernetes/test-infra#12414

Workaround as noted by golang/go#11939 (comment):

It appears there are only two ways to have omitempty work with a struct.

• Use a pointer to the struct where the pointer is nil rather than a zero value struct.
• Implement Marshaler interface for the surrounding type to provide special handling for zero value structs

The later can be somewhat cumbersome to maintain field parity for large structures. The former means data is no longer contiguous and requires care for multi-threaded use.

[atc0005]

Further reading:

• https://stackoverflow.com/questions/33447334/golang-json-marshal-how-to-omit-empty-nested-struct
• https://stackoverflow.com/questions/18088294/how-to-not-marshal-an-empty-struct-into-json-with-go
• https://www.sohamkamani.com/golang/2018-07-19-golang-omitempty/

[atc0005]

I believe that I saw this topic mentioned recently, either as Go 1.15 item or perhaps related to Generics?