StrongOf.Json 3.1.2

StrongOf.Json

System.Text.Json converters for StrongOf types. The converters support NativeAOT and trimming. Applications must supply generated JSON metadata as shown below.

NativeAOT and source generation

Install StrongOf.Json and use a JsonSerializerContext for every serialized DTO. Put the converter attribute on the strong type itself when StrongOf generates that type in the same project:

using System.Text.Json;
using System.Text.Json.Serialization;
using StrongOf.Json;
using StrongOf.SourceGeneration;

UserDto user = new() { Id = UserId.From(Guid.NewGuid()) };
string json = JsonSerializer.Serialize(user, AppJsonContext.Default.UserDto);
UserDto restored = JsonSerializer.Deserialize(json, AppJsonContext.Default.UserDto)!;

[StrongGuid]
[JsonConverter(typeof(StrongGuidJsonConverter<UserId>))]
public sealed partial class UserId;

public sealed class UserDto
{
    public UserId Id { get; set; } = null!;
}

[JsonSerializable(typeof(UserDto))]
internal partial class AppJsonContext : JsonSerializerContext;

Set these properties in the application project:

<PropertyGroup>
  <PublishAot>true</PublishAot>
  <JsonSerializerIsReflectionEnabledByDefault>false</JsonSerializerIsReflectionEnabledByDefault>
</PropertyGroup>

The StrongOf and System.Text.Json generators cannot inspect each other's generated implementation in the same compilation. A converter only on a DTO property is therefore insufficient for a newly generated strong type: the JSON generator can otherwise emit a call to a nonexistent parameterless constructor (CS7036). The explicit converter attribute on the strong type avoids this. Property-level converters remain useful for hand-written types or types already compiled in another assembly, such as StrongOf.Domains.

Options-based registration

Options still need a generated metadata resolver. For a type-level converter as above:

JsonSerializerOptions options = new()
{
    WriteIndented = true,
    TypeInfoResolver = AppJsonContext.Default,
};
AppJsonContext context = new(options);
string json = JsonSerializer.Serialize(user, context.UserDto);

For hand-written or precompiled strong types, converters may also be added to options.Converters. Registering converters alone does not supply metadata for containing DTOs. Avoid reflection-based serializer overloads in NativeAOT applications; pass the generated JsonTypeInfo<T> or JsonSerializerContext instead.

Available converters and wire format

DateTimeOffset input accepts seconds with zero to seven fractional digits and either Z or an explicit offset (+02:00, -05:30). Output uses the round-trip o format. An input without an offset is rejected. The existing converters return null for unparseable string values; callers must validate required fields.

Executable example

The NativeAOT sample publishes and runs round trips for all eleven converters with JSON reflection disabled.

Installation

dotnet add package StrongOf.Json