Document JsonKey.extra

Author: hacker1024

json_annotation/lib/src/json_key.dart

@@ -90,6 +90,13 @@ class JsonKey {
   /// Valid only on enum fields with a compatible enum value.
   final Object? unknownEnumValue;
 
+  /// `true` if this field should not be serialized.
+  ///
+  /// Fields annotated with [extra] set to true will not be included in JSON
+  /// output, and their values may be passed in as additional arguments
+  /// alongside JSON data in the deserialization function.
+  ///
+  /// If `null` (the default) or false, this argument has no effect.
   final bool? extra;
 
   /// Creates a new [JsonKey] instance.

json_serializable/README.md

@@ -94,6 +94,7 @@ is generated:
 |                            |                                             | [JsonKey.required]          |
 |                            |                                             | [JsonKey.toJson]            |
 |                            |                                             | [JsonKey.unknownEnumValue]  |
+|                            |                                             | [JsonKey.extra]             |
 
 [JsonSerializable.anyMap]: https://pub.dev/documentation/json_annotation/latest/json_annotation/JsonSerializable/anyMap.html
 [JsonSerializable.checked]: https://pub.dev/documentation/json_annotation/latest/json_annotation/JsonSerializable/checked.html
@@ -114,6 +115,7 @@ is generated:
 [JsonKey.required]: https://pub.dev/documentation/json_annotation/latest/json_annotation/JsonKey/required.html
 [JsonKey.toJson]: https://pub.dev/documentation/json_annotation/latest/json_annotation/JsonKey/toJson.html
 [JsonKey.unknownEnumValue]: https://pub.dev/documentation/json_annotation/latest/json_annotation/JsonKey/unknownEnumValue.html
+[JsonKey.extra]: https://pub.dev/documentation/json_annotation/latest/json_annotation/JsonKey/extra.html
 
 > Note: every `JsonSerializable` field is configurable via `build.yaml` –
   see the table for the corresponding key.