Default Values

Null Default

When the smithy.api#default trait annotating a shape contains a null value, and the shape is not additionally annotated explicitly as nullable, Smithy4s will (where possible) assume a "zero value" as the default. For example:

structure Test {
  @default // same thing as @default(null)
  one: String
}

Here the default for the field one will be assumed to be an empty string (""). Below is a table showing what all the zero values are for each different Smithy shape type:

Smithy Type	Zero Value
blob	Array.empty
boolean	false
string	""
byte	0
short	0
integer	0
long	0
float	0
double	0
bigInteger	0
bigDecimal	0
timestamp	0 epoch (01 Jan 1970)
document	Document.DNull
enum	N/A
intEnum	N/A
list	List.empty
map	Map.empty
structure	N/A
union	N/A
service	N/A
operation	N/A
resource	N/A

Not every shape type has a corresponding zero value. For example, there is no reasonable zero value for a structure or a union type. As such, they will not have a zero value set even if they are marked with a null default trait.