Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[Unreleased]

JsonSubTypes.Text.Json

Added

• New JsonSubTypeConverterAttribute convenience constructors that close the generic JsonSubtypes<T> converter over the annotated type, so the base type does not need to be repeated: [JsonSubTypeConverter("Kind")] instead of [JsonSubTypeConverter(typeof(JsonSubtypes<Animal>), "Kind")].

  Changed

• Renamed FallBackSubTypeAttribute to FallbackSubTypeAttribute and FallBackToNearestAncestor() to FallbackToNearestAncestor() for consistent capitalization. The FallBack* names still work in JsonSubTypes (Newtonsoft), which keeps its historical API.

  Fixed

• The attribute-based converter now writes the discriminator on serialization, as documented: the attribute’s CreateConverter override was previously bypassed by System.Text.Json (the converter was built through its parameterless constructor), so the discriminator was only read, never written. The attribute now routes through CreateConverter, which also activates the discriminator-injection write path for registered subtypes.

[2.2.0] - 2026-10-07

JsonSubTypes

Added

• JsonSubtypesConverter exposes protected static bool IsClosedGenericFormOf(Type objectType, Type genericType), so custom converters built on the public base can reuse the closed-generic base matching.

Fixed

• Deserialization with an open generic base type (e.g. Base<>) now closes the generic subtype correctly (e.g. Nested1<int> for Base<int>) instead of failing. #177
• Errors and exceptions raised while deserializing a subtype now carry the fully qualified JSON path (e.g. Property2.Value instead of Value), matching stock Newtonsoft.Json error handling. #182

Changed

• Faster deserialization and serialization, output unchanged: the attribute-derived subtype mapping and property-presence list are cached per type, single-level type resolution skips the multi-level converter walk, and string/int discriminators are converted directly instead of round-tripping through JToken.FromObject/ToObject reflection. A custom JsonConverter registered on the serializer for the discriminator type still takes the serializer-aware path on both read and write. Measured with BenchmarkDotNet on net10: single deserialize 2.54µs → 2.33µs, collection deserialize 10.21µs → 7.72µs, single serialize 1.54µs → 1.31µs, collection serialize 5.51µs → 4.86µs.
• Generic subtype matching is restricted to the base class hierarchy: CanConvert no longer claims types that merely implement an unrelated generic interface of the base type.
• The name-based resolution risk (declared only when no subtype mapping exists) is documented on the converters, so it shows up in the IDE, and in the README security section.

Security

• netstandard1.3: System.Net.Http and System.Text.RegularExpressions are pinned to the patched 4.3.4 and 4.3.1; NETStandard.Library 1.6.1 otherwise resolves them to the vulnerable 4.3.0 versions.

[1.0.0-rc.4] - 2026-10-07

JsonSubTypes.Text.Json

Changed

• The converter caches the resolved IJsonSubtypes converter list per JsonSerializerOptions (frozen on first use) and resolves single-level hierarchies without per-object allocations.
• Deserialization reads the resolved subtype from the already-parsed JsonElement instead of re-reading the raw bytes through a second materialization.
• The discriminator write path streams the payload as UTF-8 (ArrayBufferWriter + Utf8JsonWriter) instead of round-tripping through a UTF-16 string.

Security

• The name-based resolution risk (declared only when no subtype mapping exists) is documented on the converter and in the README security section.

[1.0.0-rc.2] - 2026-10-07

JsonSubTypes.Text.Json.Aot

Changed

• Breaking (pre-1.0): the package is renamed JsonSubTypes.Aot → JsonSubTypes.Text.Json.Aot: new NuGet package id, new project/namespace, and the generated-code namespace becomes JsonSubTypes.Text.Json.Aot.Generated instead of JsonSubTypes.Aot.Generated. Update the PackageReference and the using directives. The previously published JsonSubTypes.Aot 1.0.0-rc.1 is superseded and receives no further updates.
• Generated converters get unique names and are emitted without a .g.cs suffix, a shared converter base class carries the common skeleton once per compilation, and the value-mode Write is hardened (redundant && true removed).
• Generator diagnostics now check the cancellation token before every report, so generation stops promptly.
• Bumped the build-time Microsoft.CodeAnalysis.CSharp dependency from 5.6.0 to 5.9.0 (not shipped in the package).

[1.0.0-rc.3] - 2026-08-12

JsonSubTypes.Text.Json

Added

• New JsonSubTypesAotConverterAttribute opting a base type into the JsonSubTypes.Text.Json.Aot source generator.

JsonSubTypes.Text.Json.Aot

Added

• New package JsonSubTypes.Text.Json.Aot (1.0.0-rc.1): a Roslyn source generator emitting compiled subtype converters. Routing (property presence, fallback, enums, nested hierarchies, dynamic registration) is compiled, so it works in Native AOT / trimmed binaries without reflection.

[1.0.0-rc.2] - 2026-08-10

Changed

• Rebuilt with Source Link, deterministic builds and .snupkg symbol packages so symbols validate against the published package.

[1.0.0-rc.1] - 2026-08-10

Added

• New package JsonSubTypes.Text.Json bringing polymorphic subtype serialization to System.Text.Json (.NET 8+).
  • Attribute-based and builder-based subtype registration.
  • Discriminator mapping by property presence (KnownSubTypeWithProperty).
  • Fallback subtype support (FallBackSubType).
  • Opt-in cross-assembly subtype resolution (JsonSubTypesTypeResolution.AddAssembly).
  • Comprehensive unit test suite with 129 test cases.

[2.1.0] - 2026-08-10

Added

• Make JsonSubtypesConverter and JsonSubtypesByDiscriminatorValueConverter public and subclassable: custom subtype converters can now be built with a custom discriminator mapping and control over discriminator serialization, instead of being limited to the fluent builder. #138

Fixed

• Deserializing dates now matches stock Newtonsoft deserialization #166 #167

Changed

• Bump Newtonsoft.Json dependency to 13.0.4
• Deterministic builds, Source Link and .snupkg symbol packages

[2.0.1] - 2022-05-09

Fixed

• Add package description with an included README.md

[2.0.0] - 2022-05-09

Changed

• Discriminator property is placed first by default now #46 #149
• Depends on the latest Newtonsoft.Json #131 #148
• Signature of SetFallbackSubtype has been changed to fix a design bug #152 #147

Added

• Allow to stop searching when a match is found #128 #151

Fixed

• Fix a DateTime issue introduced in release 1.8.0 #120 #128

[1.9.0] - 2022-05-09

Added

• Add version of builder methods with generic types for cleaner syntax. #110
• Support (serializing) sub types with generic type parameters when using JsonSubtypesConverterBuilder #135
• Add cache of type’s attributes #119

Fixed

• Newtonsoft.Json dependency version should be lowest supported, not latest available #101
• Multiple type discriminators in JSON silently passes. #100
• Incorrect handling of datetime field in a sub-type #114
• Too many target framework inside the nuget package #48
• Copy MaxDepth when creating internal JObjectReader #137
• Fix deserialization of hierarchy with multiple levels #118

[1.8.0] - 2020-09-24

Added

• Add version of builder methods with generic types for cleaner syntax. #115

Fixed

• Newtonsoft.Json dependency version should be lowest supported, not latest available #101
• Multiple type discriminators in JSON silently passes. #100
• Incorrect handling of datetime field in a sub-type #114

[1.7.0] - 2020-03-28

Added

• Fallback to JSONPath to allow nested field as a deserialization property. #89
• Bump Newtonsoft.Json from 11.0.2 to 12.0.3 #88
• Implements dynamic registration for subtype detection by property presence. #50

Fixed

• JsonSubtypes does not respect naming strategy for discriminator property value #80
• Fix infinite loop when specifying name of abstract base class as discriminator #83
• Serializing base class with discriminator property results in KeyNotFoundException #79

[1.6.0] - 2019-06-25

Added

• Support for multiple discriminators on single type #66
• Support for per inheritance level discriminators #60
• Support specifying a falback sub type if none matched #63
• Provide NuGet package with strong name #75
• Changelog history and documentation arround versionning

[1.5.2] - 2019-01-19

Security

• Arbitrary constructor invocation #56

[1.5.1] - 2018-10-15

Fixed

• Read.me was imported by the nuget install #51

[1.5.0] - 2018-08-27

Added

• Ability to set the discriminator property order to first (see #46)
• Compatibility with JSON.NET 11.0.2 (see #47)

[1.4.0] - 2018-04-18

Added

• Support for both camel case and non camel case parameters #31
• Explicit support for netstandard2.0 #34

Fixed

• Code refactoring to reduce the number of conditional compilation statements #36

[1.3.1] - 2014-04-12

Fixed

• fixed exception that was returned instead of thrown #32

[1.3.0] - 2018-29-01

Added

• De-/Serialization for sub-types without “type” property #13
• Option for avoiding mapping on the Parent #26

Fixed

• Sonar (Coverage) analysis is broken #23

[1.1.3] - 2017-11-15

Fixed

• fixed support of framework net40 #21

[1.1.2] - 2017-11-20

Fixed

• fix #18 : Deserialisation is not thread safe

[1.1.1] - 2017-09-22

Fixed

• fix #11 Nuget packages doesn’t work for .Net Framework projects

[1.1.0] - 2017-09-19

Added

• Parse string enum values #9.

[1.0.0] - 2017-07-23

Initial release !