disallowNullValue property
If true, generated code will throw a DisallowedNullValueException if
the corresponding key exists, but the value is null.
Note: this value does not affect the behavior of a JSON map without the associated key.
If disallowNullValue is true, includeIfNull will be treated as
false to ensure compatibility between toJson and fromJson.
If both includeIfNull and disallowNullValue are set to true on the
same field, an exception will be thrown during code generation.
Implementation
final bool? disallowNullValue;