[dotnet] Enable Option<T> to work when no value is provided

dotnet/src/webdriver/BiDi/BrowsingContext/BrowsingContextModule.cs

@@ -86,7 +86,7 @@ public async Task<ReloadResult> ReloadAsync(BrowsingContext context, ReloadOptio
 
     public async Task<SetViewportResult> SetViewportAsync(BrowsingContext context, SetViewportOptions? options = null)
     {
-        var @params = new SetViewportParameters(context, options?.Viewport, options?.DevicePixelRatio);
+        var @params = new SetViewportParameters(context, options?.Viewport ?? Optional<Viewport?>.None, options?.DevicePixelRatio ?? Optional<double?>.None);
 
         return await Broker.ExecuteCommandAsync(new SetViewportCommand(@params), options, _jsonContext.SetViewportCommand, _jsonContext.SetViewportResult).ConfigureAwait(false);
     }
@@ -292,4 +292,6 @@ protected override void Initialize(JsonSerializerOptions options)
 [JsonSerializable(typeof(NavigationInfo))]
 [JsonSerializable(typeof(UserPromptOpenedEventArgs))]
 [JsonSerializable(typeof(UserPromptClosedEventArgs))]
+[JsonSerializable(typeof(Viewport?))]
+[JsonSerializable(typeof(double?))]
 internal partial class BrowsingContextJsonSerializerContext : JsonSerializerContext;

dotnet/src/webdriver/BiDi/BrowsingContext/SetViewportCommand.cs

@@ -17,21 +17,23 @@
 // under the License.
 // </copyright>
 
-using OpenQA.Selenium.BiDi.Json.Converters;
 using System.Text.Json.Serialization;
 
 namespace OpenQA.Selenium.BiDi.BrowsingContext;
 
 internal sealed class SetViewportCommand(SetViewportParameters @params)
     : Command<SetViewportParameters, SetViewportResult>(@params, "browsingContext.setViewport");
 
-internal sealed record SetViewportParameters(BrowsingContext Context, [property: JsonConverter(typeof(OptionalConverter<Viewport?>))] Optional<Viewport?>? Viewport, [property: JsonConverter(typeof(OptionalConverter<double?>))] Optional<double?>? DevicePixelRatio) : Parameters;
+internal sealed record SetViewportParameters(
+    BrowsingContext Context,
+    [property: JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)] Optional<Viewport?> Viewport,
+    [property: JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)] Optional<double?> DevicePixelRatio) : Parameters;
 
 public sealed class SetViewportOptions : CommandOptions
 {
-    public Optional<Viewport?>? Viewport { get; set; }
+    public Optional<Viewport?> Viewport { get; set; }
 
-    public Optional<double?>? DevicePixelRatio { get; set; }
+    public Optional<double?> DevicePixelRatio { get; set; }
 }
 
 public readonly record struct Viewport(long Width, long Height);

dotnet/src/webdriver/BiDi/Json/Converters/OptionalConverterFactory.cs

@@ -0,0 +1,65 @@
+// <copyright file="OptionalConverterFactory.cs" company="Selenium Committers">
+// Licensed to the Software Freedom Conservancy (SFC) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The SFC licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+// </copyright>
+
+using System;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using System.Text.Json.Serialization.Metadata;
+
+namespace OpenQA.Selenium.BiDi.Json.Converters;
+
+internal sealed class OptionalConverterFactory : JsonConverterFactory
+{
+    public override bool CanConvert(Type typeToConvert) => typeToConvert.IsGenericType && typeToConvert.GetGenericTypeDefinition() == typeof(Optional<>);
+
+    public override JsonConverter? CreateConverter(Type typeToConvert, JsonSerializerOptions options)
+    {
+        var converter = (JsonConverter?)Activator.CreateInstance(typeof(OptionalConverter<>).MakeGenericType(typeToConvert.GenericTypeArguments[0]));
+
+        return converter;
+    }
+
+    internal sealed class OptionalConverter<T> : JsonConverter<Optional<T>>
+    {
+        public override bool HandleNull => true;
+
+        public override Optional<T> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            var converter = (JsonTypeInfo<T>)options.GetTypeInfo(typeof(T));
+
+            T? value = JsonSerializer.Deserialize<T>(ref reader, converter);
+            return new Optional<T>(value);
+        }
+
+        public override void Write(Utf8JsonWriter writer, Optional<T> value, JsonSerializerOptions options)
+        {
+            if (value.TryGetValue(out var optionalValue))
+            {
+                var converter = (JsonTypeInfo<T?>)options.GetTypeInfo(typeof(T?));
+
+                JsonSerializer.Serialize(writer, optionalValue, converter);
+            }
+            else
+            {
+                throw new JsonException("This property should be annotated with [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]");
+            }
+        }
+    }
+}
+

dotnet/src/webdriver/BiDi/Optional.cs

@@ -17,31 +17,36 @@
 // under the License.
 // </copyright>
 
+using OpenQA.Selenium.BiDi.Json.Converters;
 using System;
+using System.Text.Json.Serialization;
 
 namespace OpenQA.Selenium.BiDi;
 
+[JsonConverter(typeof(OptionalConverterFactory))]
 public readonly record struct Optional<T>
 {
-    private readonly T _value;
+    private readonly T? _value;
     public bool HasValue { get; }
 
-    public T Value => HasValue
+    public T? Value => HasValue
         ? _value
-        : throw new InvalidOperationException("Optional has no value. Check IsSet first.");
+        : throw new InvalidOperationException($"Optional has no value. Check {nameof(HasValue)} first.");
 
-    public Optional(T value)
+    public Optional(T? value)
     {
         _value = value;
         HasValue = true;
     }
 
-    public bool TryGetValue(out T value)
+    public bool TryGetValue(out T? value)
     {
         value = _value;
         return HasValue;
     }
 
+    public static Optional<T> None => default;
+
     // implicit conversion from T -> Optional<T>
-    public static implicit operator Optional<T>(T value) => new(value);
+    public static implicit operator Optional<T>(T? value) => new(value);
 }

dotnet/test/common/BiDi/BrowsingContext/BrowsingContextTest.cs

@@ -316,7 +316,7 @@ public async Task CanSetViewport()
         Assert.That(await GetHeightAsync(), Is.EqualTo(300));
 
         await context.SetViewportAsync(new() { Viewport = new Viewport(250, 300) });
-        await context.SetViewportAsync(new() { Viewport = default }); // Sends nothing
+        await context.SetViewportAsync(new() { Viewport = Optional<Viewport?>.None }); // Sends nothing
 
         Assert.That(await GetWidthAsync(), Is.EqualTo(250));
         Assert.That(await GetHeightAsync(), Is.EqualTo(300));