dotnet/src/webdriver/BiDi/Json/JsonExtensions.cs

// <copyright file="JsonExtensions.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
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// </copyright>

using System.Text.Json;
using System.Text.Json.Serialization.Metadata;

namespace OpenQA.Selenium.BiDi.Json;

internal static class JsonExtensions
{
    public static string GetDiscriminator(this ref Utf8JsonReader reader, string name)
    {
        Utf8JsonReader readerClone = reader;

        if (readerClone.TokenType != JsonTokenType.StartObject)
            throw new JsonException($"Cannot determine the discriminator of {readerClone.TokenType} token type while supported is {JsonTokenType.StartObject} only.");

        string? discriminator = null;

        readerClone.Read(); // move past StartObject to first PropertyName
        while (readerClone.TokenType == JsonTokenType.PropertyName)
        {
            if (readerClone.ValueTextEquals(name))
            {
                readerClone.Read(); // move to the property value
                discriminator = readerClone.GetString();

                break;
            }

            readerClone.Read(); // move to the property value
            readerClone.Skip(); // skip the value (including nested objects/arrays)
            readerClone.Read(); // move to the next PropertyName or EndObject
        }

        return discriminator ?? throw new JsonException($"Couldn't determine '{name}' discriminator.");
    }

    public static JsonTypeInfo<T> GetTypeInfo<T>(this JsonSerializerOptions options)
    {
        if (options.TryGetTypeInfo(typeof(T), out JsonTypeInfo? typeInfo))
        {
            return (JsonTypeInfo<T>)typeInfo;
        }

        throw new JsonException($"Type info for '{typeof(T).FullName}' is not available in the serializer context. Ensure the type is included in the JsonSerializerContext.");
    }
}