Optionals

[ufukty]

Current behavior

Currently marking targets as optionals is not possible. The resulting struct will contain basic/composed type regardless.

struct Config type {
  A int `yaml:"a"`
}

Proposed behavior

Providing an interface to user to let specify which targets can be optional. Then, implement additional types based on contains the value as a field, and also contains the state of value in another field, named IsSet.

type Optional[T any] struct {
  Value T
  IsSet bool
}

struct Config type {
  A Optional[int] `yaml:"a"`
}

See also

• sql.Null type providing Go users a method to distinguish set and zero values returns from queries with Go generics
• Issue for sq.Null
• Feature request for assigning pointers to optional-marked targets

[ufukty]

One method is allowing user to manually assign type, than using types like null.String will provide the functionality.

[ufukty]

One issue on Mholt's mentions using pointers for null checking. It could be a directive like { pointer: true } or { modify: pointer } which would support adding more modifications in future.

mholt/json-to-go#36