Serialize/Deserialize RichText instances for plain-text and array forms

src/library/Telegram.BotAPI/Converters/RichTextConverter.cs

@@ -1,6 +1,7 @@
 // Copyright (c) 2026 Quetzal Rivera.
 // Licensed under the MIT License, See LICENCE in the project root for license information.
 
+using System.Text.Json;
 using Telegram.BotAPI.RichMessages;
 
 namespace Telegram.BotAPI.Converters;
@@ -12,4 +13,41 @@ public sealed class RichTextConverter : DiscriminatorJsonConverter<RichText>
 {
     /// <inheritdoc />
     public override string PropertyName => PropertyNames.Type;
+
+    /// <inheritdoc/>
+    public override RichText? Read(
+        ref Utf8JsonReader reader,
+        Type typeToConvert,
+        JsonSerializerOptions options
+    )
+    {
+        return reader.TokenType switch
+        {
+            JsonTokenType.StartArray => new RichTextArray(
+                JsonSerializer.Deserialize<RichText[]>(ref reader, options)!
+            ),
+            JsonTokenType.String => new RichTextPlainText(reader.GetString()!),
+            JsonTokenType.StartObject => base.Read(ref reader, typeToConvert, options),
+            _ => throw new JsonException(
+                $"Failed to deserialize RichText. Unexpected token {reader.TokenType}"
+            ),
+        };
+    }
+
+    /// <inheritdoc/>
+    public override void Write(Utf8JsonWriter writer, RichText value, JsonSerializerOptions options)
+    {
+        if (value is RichTextArray array)
+        {
+            JsonSerializer.Serialize(writer, (IEnumerable<RichText>)array, options);
+        }
+        else if (value is RichTextPlainText plainText)
+        {
+            JsonSerializer.Serialize(writer, (string)plainText, options);
+        }
+        else
+        {
+            base.Write(writer, value, options);
+        }
+    }
 }

src/library/Telegram.BotAPI/RichMessages/RichText/RichText.cs

@@ -38,7 +38,7 @@ namespace Telegram.BotAPI.RichMessages;
 /// </list>
 /// </summary>
 [JsonConverter(typeof(RichTextConverter))]
-public abstract class RichText
+public abstract partial class RichText
 {
     /// <summary>
     /// Type of the rich text

src/library/Telegram.BotAPI/RichMessages/RichText/RichTextArray.cs

@@ -0,0 +1,32 @@
+using System.Collections;
+using Telegram.BotAPI.Converters;
+
+namespace Telegram.BotAPI.RichMessages;
+
+/// <summary>
+/// Represents an array of <see cref="RichText"/>.
+/// </summary>
+[JsonConverter(typeof(RichTextConverter))]
+public class RichTextArray(IEnumerable<RichText> items) : RichText, IEnumerable<RichText>
+{
+    /// <summary>
+    /// Type of the rich text
+    /// </summary>
+    public override string Type => "RichTextArray";
+
+    private readonly IEnumerable<RichText> items = items;
+
+    /// <inheritdoc/>
+    public IEnumerator<RichText> GetEnumerator() => this.items.GetEnumerator();
+
+    IEnumerator IEnumerable.GetEnumerator() => this.GetEnumerator();
+}
+
+public partial class RichText
+{
+#pragma warning disable IDE0023 // Use block body for conversion operator
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
+    public static implicit operator RichText(RichText[] value) => new RichTextArray(value);
+#pragma warning restore CS1591 // Missing XML comment for publicly visible type or member
+#pragma warning restore IDE0023 // Use block body for conversion operator
+}

src/library/Telegram.BotAPI/RichMessages/RichText/RichTextPlainText.cs

@@ -0,0 +1,36 @@
+using System.Diagnostics;
+using Telegram.BotAPI.Converters;
+
+namespace Telegram.BotAPI.RichMessages;
+
+/// <summary>
+/// Plain text
+/// </summary>
+[JsonConverter(typeof(RichTextConverter))]
+[DebuggerDisplay("{value}")]
+public class RichTextPlainText(string plainText) : RichText
+{
+    /// <summary>
+    /// Type of the rich text
+    /// </summary>
+    public override string Type => "RichTextPlainText";
+
+    private readonly string value = plainText;
+
+    /// <inheritdoc/>
+    public override string ToString() => this.value;
+
+#pragma warning disable CS1591 // Missing XML comment for publicly visible type or member
+#pragma warning disable IDE0023 // Use block body for conversion operator
+    public static implicit operator RichTextPlainText(string value) => new(value);
+
+    public static implicit operator string(RichTextPlainText instance) => instance.value;
+}
+
+public partial class RichText
+{
+    public static implicit operator RichText(string value) => new RichTextPlainText(value);
+}
+
+#pragma warning restore IDE0023 // Use block body for conversion operator
+#pragma warning restore CS1591 // Missing XML comment for publicly visible type or member

src/library/Telegram.BotAPI/Telegram.BotAPI.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
-    <Version>10.3.0</Version>
+    <Version>10.3.1</Version>
     <PackageId>$(AssemblyName)</PackageId>
     <Authors>Quetzal Rivera</Authors>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
@@ -25,7 +25,8 @@
     <PackageProjectUrl>https://github.com/Eptagone/Telegram.BotAPI</PackageProjectUrl>
     <RepositoryType></RepositoryType>
     <AssemblyName>Telegram.BotAPI</AssemblyName>
-    <PackageReleaseNotes>Updated to Bot API v10.3</PackageReleaseNotes>
+    <PackageReleaseNotes>Fix serialization/deserialization of RichText types when the value is a
+      plain text or an array of RichText instances</PackageReleaseNotes>
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
     <AnalysisLevel>latest-recommended</AnalysisLevel>
     <PackageReadmeFile>README.md</PackageReadmeFile>

src/tests/Telegram.BotAPI.Tests/Serialization.cs

@@ -5,6 +5,7 @@
 using System.Text.Json;
 using System.Text.Json.Serialization;
 using Telegram.BotAPI.InlineMode;
+using Telegram.BotAPI.RichMessages;
 using Telegram.BotAPI.UpdatingMessages;
 
 namespace Telegram.BotAPI.Tests;
@@ -97,4 +98,15 @@ [new InlineKeyboardButton("Button") { CallbackData = "data" }],
             ).MessageText
         );
     }
+
+    [Fact]
+    public void DeserializeRichText()
+    {
+        var json =
+            """[{"type":"bold","text":"hi"},{"type":"italic","text":["a",{"type":"bold","text":"b"}]}]""";
+        var instances = JsonSerializer.Deserialize<RichText[]>(json);
+        var serializedInstances = JsonSerializer.Serialize(instances);
+
+        Assert.Equal(json, serializedInstances);
+    }
 }