Can be specified only if this field is repeated. If unspecified, it falls back to the file option named collection_type, which defaults to scala.collection.Seq.
keyType
If the field is a map, you can specify custom Scala types for the key or value.
mapType
Can be specified only if this field is a map. If unspecified, it falls back to the file option named map_type which defaults to scala.collection.immutable.Map
noBox
Do not box this value in Option[T]. If set, this overrides MessageOptions.no_box
noDefaultValueInConstructor
If true, no default value will be generated for this field in the message constructor. If this field is set, it has the highest precedence and overrides the values at the message-level and file-level.
required
Like no_box it does not box a value in Option[T], but also fails parsing when a value is not provided. This enables to emulate required fields in proto3.