## Summary Add support in FPC for the modern Delphi JSON serialization framework introduced in Delphi 10.3 Rio (`System.JSON.Serializers`), including full support for generic serialization/deserialization of objects, collections, and complex types. Delphi’s modern JSON serializer provides attribute-based configuration, automatic handling of generics, converters, contract resolution, and a high-level API via `TJsonSerializer`. This greatly simplifies JSON ↔ object mapping compared to manually constructing JSON using `fcl-json`. Free Pascal already provides `System.JSON`, but it lacks: - System.JSON.Serializers - System.JSON.Types - System.JSON.Readers - System.JSON.Writers - System.JSON.Converters - Attribute-based serialization ecosystem - Generic-aware serialization/deserialization ## System Information Not platform-specific. Applies to all FPC-supported platforms. ## Relevant 3rd-party Information ### Delphi Documentation Modern JSON serialization in Delphi: https://docwiki.embarcadero.com/Libraries/Florence/en/System.JSON https://docwiki.embarcadero.com/Libraries/Florence/en/System.JSON.Serializers ### Delphi Version Compatibility Modern serializer first appeared in: - Delphi 10.3 Rio Includes: - `System.JSON.Serializers` - `TJsonSerializer` - `TJsonTypeInfo`, `TJsonConverter`, `TJsonReader`, `TJsonWriter`, etc. - Full generic support for JSON serialization/deserialization - Attribute-based serialization (`JsonName`, `JsonNumberHandling`, converters, etc.) ## Example Project ```pascal type TPerson = class public Name: string; Age: Integer; end; var P: TPerson; Json: string; begin P := TPerson.Create; P.Name := 'Alice'; P.Age := 30; Json := TJsonSerializer.Serialize<TPerson>(P); // {"Name":"Alice","Age":30} P := TJsonSerializer.Deserialize<TPerson>(Json); end; ``` ## Motivation - Improves modern Delphi compatibility - Enables cross-compilation of Delphi codebases - Provides robust attribute-based JSON serialization for FPC