Add DateOnly and TimeOnly support (#2)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: ScarletKuro <19953225+ScarletKuro@users.noreply.github.com>

Author: Copilot

AGENT.md

@@ -11,7 +11,7 @@ This document provides guidance for AI agents and developers working on the **Sc
 - Custom date/time format attributes (`JsonDateTimeConverterAttribute` for reflection, `JsonDateTimeFormatAttribute` for source generators)
 - Source generator-compatible format converters (`JsonDateTimeFormatConverter<T>`)
 - .NET 9+ contract customization resolver (`DateTimeConverterResolver`)
-- Support for `DateTime`, `DateTimeOffset`, and nullable variants
+- Support for `DateTime`, `DateTimeOffset`, `DateOnly`, `TimeOnly`, and nullable variants
 - Multi-target framework support (.NET 6, 7, 8, 9, 10)
 
 ## Repository Structure
@@ -31,7 +31,11 @@ Scarlet.System.Text.Json.DateTimeConverter/
 │   │   │   ├── DateTimeConverter.cs
 │   │   │   ├── DateTimeNullableConverter.cs
 │   │   │   ├── DateTimeOffsetConverter.cs
-│   │   │   └── DateTimeOffsetNullableConverter.cs
+│   │   │   ├── DateTimeOffsetNullableConverter.cs
+│   │   │   ├── DateOnlyConverter.cs
+│   │   │   ├── DateOnlyNullableConverter.cs
+│   │   │   ├── TimeOnlyConverter.cs
+│   │   │   └── TimeOnlyNullableConverter.cs
 │   │   ├── DateTimeConverterFactoryHelper.cs
 │   │   ├── DateTimeConverterResolver.cs  # .NET 9+ contract customization
 │   │   ├── IJsonDateTimeFormat.cs
@@ -187,11 +191,15 @@ The project uses a standard GitHub workflow:
 
 #### 1. Converters (Internal)
 
-Four internal converter classes handle actual JSON serialization/deserialization:
+Eight internal converter classes handle actual JSON serialization/deserialization:
 - `DateTimeConverter` - for `DateTime`
 - `DateTimeNullableConverter` - for `DateTime?`
 - `DateTimeOffsetConverter` - for `DateTimeOffset`
 - `DateTimeOffsetNullableConverter` - for `DateTimeOffset?`
+- `DateOnlyConverter` - for `DateOnly`
+- `DateOnlyNullableConverter` - for `DateOnly?`
+- `TimeOnlyConverter` - for `TimeOnly`
+- `TimeOnlyNullableConverter` - for `TimeOnly?`
 
 All use `CultureInfo.InvariantCulture` for consistent formatting.
 
@@ -269,7 +277,7 @@ Tests verify four distinct usage patterns:
 4. **Source generator with resolver (old attribute)** - Uses `JsonDateTimeConverterAttribute` + `DateTimeConverterResolver` (.NET 9+, with SYSLIB1223 warnings for backward compatibility)
 
 Each pattern is tested with:
-- Individual types (`DateTime`, `DateTime?`, `DateTimeOffset`, `DateTimeOffset?`)
+- Individual types (`DateTime`, `DateTime?`, `DateTimeOffset`, `DateTimeOffset?`, `DateOnly`, `DateOnly?`, `TimeOnly`, `TimeOnly?`)
 - Complete models
 - Null value handling
 

README.md

@@ -4,7 +4,7 @@
 [![Nuget](https://img.shields.io/nuget/dt/Scarlet.System.Text.Json.DateTimeConverter?color=ff4081&label=nuget%20downloads&logo=nuget)](https://www.nuget.org/packages/Scarlet.System.Text.Json.DateTimeConverter)
 [![GitHub](https://img.shields.io/github/license/ScarletKuro/Scarlet.System.Text.Json.DateTimeConverter?color=594ae2&logo=github)](https://github.com/ScarletKuro/Scarlet.System.Text.Json.DateTimeConverter/blob/master/LICENSE)
 
-A flexible and powerful library for customizing `DateTime` and `DateTimeOffset` serialization in System.Text.Json, with full support for both reflection-based and source generator approaches.
+A flexible and powerful library for customizing `DateTime`, `DateTimeOffset`, `DateOnly`, and `TimeOnly` serialization in System.Text.Json, with full support for both reflection-based and source generator approaches.
 
 ## Table of Contents
 
@@ -24,7 +24,7 @@ A flexible and powerful library for customizing `DateTime` and `DateTimeOffset`
 
 ## Overview
 
-This package provides four ways to specify custom date formats for `DateTime`, `DateTimeOffset`, and their nullable counterparts when serializing and deserializing JSON using `System.Text.Json`:
+This package provides four ways to specify custom date formats for `DateTime`, `DateTimeOffset`, `DateOnly`, `TimeOnly`, and their nullable counterparts when serializing and deserializing JSON using `System.Text.Json`:
 
 1. **`JsonDateTimeConverterAttribute`** - Simple attribute-based approach (reflection only, or .NET 9+ with resolver but produces warnings)
 2. **`JsonDateTimeFormatAttribute`** - Clean attribute for source generators with .NET 9+ resolver (no warnings)
@@ -102,19 +102,27 @@ public class Order
 
     [JsonDateTimeConverter("yyyy-MM-ddTHH:mm:ss.fffZ")]
     public DateTimeOffset ShippedAt { get; set; }
+
+    [JsonDateTimeConverter("MM/dd/yyyy")]
+    public DateOnly DeliveryDate { get; set; }
+
+    [JsonDateTimeConverter("HH:mm")]
+    public TimeOnly DeliveryTime { get; set; }
 }
 
 // Usage
 var order = new Order
 {
     OrderDate = new DateTime(2026, 1, 15),
     ProcessedDate = new DateTime(2026, 1, 15, 14, 30, 0),
-    ShippedAt = DateTimeOffset.UtcNow
+    ShippedAt = DateTimeOffset.UtcNow,
+    DeliveryDate = new DateOnly(2026, 1, 20),
+    DeliveryTime = new TimeOnly(10, 30)
 };
 
 string json = JsonSerializer.Serialize(order);
 Console.WriteLine(json);
-// Output: {"OrderDate":"2026-01-15","ProcessedDate":"2026-01-15T14:30:00","ShippedAt":"2026-01-15T14:30:00.123Z"}
+// Output: {"OrderDate":"2026-01-15","ProcessedDate":"2026-01-15T14:30:00","ShippedAt":"2026-01-15T14:30:00.123Z","DeliveryDate":"01/20/2026","DeliveryTime":"10:30"}
 
 var deserializedOrder = JsonSerializer.Deserialize<Order>(json);
 ```
@@ -150,6 +158,12 @@ public class Order
 
     [JsonConverter(typeof(JsonDateTimeFormatConverter<DateFormats.ISO8601>))]
     public DateTimeOffset ShippedAt { get; set; }
+
+    [JsonConverter(typeof(JsonDateTimeFormatConverter<DateFormats.DateOnlySlash>))]
+    public DateOnly DeliveryDate { get; set; }
+
+    [JsonConverter(typeof(JsonDateTimeFormatConverter<DateFormats.TimeOnlyShort>))]
+    public TimeOnly DeliveryTime { get; set; }
 }
 
 // Define your custom date formats
@@ -169,6 +183,16 @@ public static class DateFormats
     {
         public static string Format => "yyyy-MM-ddTHH:mm:ss.fffZ";
     }
+
+    public class DateOnlySlash : IJsonDateTimeFormat
+    {
+        public static string Format => "MM/dd/yyyy";
+    }
+
+    public class TimeOnlyShort : IJsonDateTimeFormat
+    {
+        public static string Format => "HH:mm";
+    }
 }
 
 // Create a JsonSerializerContext for source generation
@@ -181,7 +205,9 @@ var order = new Order
 {
     OrderDate = new DateTime(2026, 1, 15),
     ProcessedDate = new DateTime(2026, 1, 15, 14, 30, 0),
-    ShippedAt = DateTimeOffset.UtcNow
+    ShippedAt = DateTimeOffset.UtcNow,
+    DeliveryDate = new DateOnly(2026, 1, 20),
+    DeliveryTime = new TimeOnly(10, 30)
 };
 
 string json = JsonSerializer.Serialize(order, typeof(Order), OrderJsonContext.Default);
@@ -225,6 +251,12 @@ public class Order
 
     [JsonDateTimeFormat("yyyy-MM-ddTHH:mm:ss.fffZ")]
     public DateTimeOffset ShippedAt { get; set; }
+
+    [JsonDateTimeFormat("MM/dd/yyyy")]
+    public DateOnly DeliveryDate { get; set; }
+
+    [JsonDateTimeFormat("HH:mm")]
+    public TimeOnly DeliveryTime { get; set; }
 }
 
 [JsonSerializable(typeof(Order))]
@@ -427,6 +459,10 @@ This matches standard `System.Text.Json` behavior.
 - `DateTime?`
 - `DateTimeOffset`
 - `DateTimeOffset?`
+- `DateOnly`
+- `DateOnly?`
+- `TimeOnly`
+- `TimeOnly?`
 
 All types support any valid [.NET date and time format string](https://learn.microsoft.com/en-us/dotnet/standard/base-types/custom-date-and-time-format-strings).