.NET 6下GraphQL 8.0.0的InvalidOperationException异常求助

运行基于.NET 6.0的代码时遇到以下异常：

Exception Occured: System.InvalidOperationException: The type 'System.ReadOnlySpan`1[System.Char]' of property 'Span' on type 'GraphQLParser.ROM' is invalid for serialization or deserialization because it is a pointer type, is a ref struct, or contains generic parameters that have not been replaced by specific types.

使用的库版本：

• graphql 8.0.0
• GraphQL-Parser 9.5.0
• GraphQL.NewtonsoftJson 8.0.0
• GraphQL.SystemTextJson 8.0.0

项目中仅在DateGraphType类内使用ROM类，代码如下：

private static DateTime ParseDate(ROM stringValue)
{
    if (DateTime.TryParseExact(
#if NETSTANDARD2_0
        (string)
#endif
        stringValue, "yyyy-MM-dd", DateTimeFormatInfo.InvariantInfo, DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal, out var date))
    {
        return date;
    }

    throw new FormatException($"Could not parse date. Expected yyyy-MM-dd. Value: {stringValue}");
}

异常发生在数据库查询完成后（而非调用查询时），尝试降级GraphQL到7.8.0、GraphQL-Parser到8.4.2后问题仍未解决，堆栈跟踪如下：

---- stack trace --
   at System.Text.Json.ThrowHelper.ThrowInvalidOperationException_CannotSerializeInvalidType(Type typeToConvert, Type declaringType, MemberInfo memberInfo)
   at System.Text.Json.Serialization.Metadata.ReflectionJsonTypeInfo`1.CreateProperty(Type typeToConvert, MemberInfo memberInfo, JsonSerializerOptions options, Boolean shouldCheckForRequiredKeyword)
   at System.Text.Json.Serialization.Metadata.ReflectionJsonTypeInfo`1.CacheMember(Type typeToConvert, MemberInfo memberInfo, Boolean& propertyOrderSpecified, Dictionary`2& ignoredMembers, Boolean shouldCheckForRequiredKeyword)
   at System.Text.Json.Serialization.Metadata.ReflectionJsonTypeInfo`1.LateAddProperties()
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo.InitializePropertyCache()
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo.Configure()
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo.<EnsureConfigured>g__ConfigureLocked|143_0()
--- End of stack trace from previous location ---
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo.<EnsureConfigured>g__ConfigureLocked|143_0()
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo.EnsureConfigured()
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo.get_JsonTypeInfo()
   at System.Text.Json.WriteStackFrame.GetNestedJsonTypeInfo()
   at System.Text.Json.WriteStack.Push()
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Converters.ArrayConverter`2.OnWriteResume(Utf8JsonWriter writer, TElement[] array, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonCollectionConverter`2.OnTryWrite(Utf8JsonWriter writer, TCollection value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWriteAsObject(Utf8JsonWriter writer, Object value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCoreAsObject(Utf8JsonWriter writer, Object value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.JsonSerializer.WriteCore[TValue](Utf8JsonWriter writer, TValue& value, JsonTypeInfo jsonTypeInfo, WriteStack& state)
   at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
   at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
   at System.Text.Json.JsonSerializer.WriteStreamAsync[TValue](Stream utf8Json, TValue value, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Mvc.Formatters.SystemTextJsonOutputFormatter.WriteResponseBodyAsync(OutputFormatterWriteContext context, Encoding selectedEncoding)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|30_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|25_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|20_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)

异常核心原因是ROM类型包含ReadOnlySpan属性，而System.Text.Json无法序列化ref struct类型。虽然仅在ParseDate方法中使用ROM，但存在某个场景（如GraphQL执行上下文、错误信息被ASP.NET Core自动序列化返回）导致ROM实例被纳入序列化流程。

可尝试以下几种解决方法：

方法1：为ROM类型添加自定义System.Text.Json转换器 #

创建转换器将ROM序列化为字符串，避免触发Span属性的序列化：

using GraphQLParser;
using System.Text.Json;
using System.Text.Json.Serialization;

public class RomJsonConverter : JsonConverter<ROM>
{
    public override ROM Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        return reader.GetString();
    }

    public override void Write(Utf8JsonWriter writer, ROM value, JsonSerializerOptions options)
    {
        writer.WriteStringValue(value.ToString());
    }
}

在Startup/Program.cs中注册转换器：

builder.Services.AddControllers()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.Converters.Add(new RomJsonConverter());
    });

方法2：避免ROM实例被序列化到响应中 #

检查代码确保数据库查询返回对象或GraphQL执行结果中无直接/间接包含ROM的属性。若为GraphQL错误携带ROM对象，可自定义错误过滤器转换为字符串：

public class CustomErrorFilter : IErrorFilter
{
    public IError OnError(IError error)
    {
        // 检查错误扩展字段，将ROM转换为字符串
        foreach (var key in error.Extensions.Keys.ToList())
        {
            if (error.Extensions[key] is ROM rom)
            {
                error.Extensions[key] = rom.ToString();
            }
        }
        return error;
    }
}

注册错误过滤器：

builder.Services.AddGraphQL(options =>
{
    options.AddErrorFilter<CustomErrorFilter>();
})
.AddSystemTextJson()
.AddGraphTypes(typeof(YourSchema));

方法3：替换ROM为字符串类型 #

若ParseDate方法调用场景允许，直接将参数改为string类型：

private static DateTime ParseDate(string stringValue)
{
    if (DateTime.TryParseExact(
        stringValue, "yyyy-MM-dd", DateTimeFormatInfo.InvariantInfo, DateTimeStyles.AssumeUniversal | DateTimeStyles.AdjustToUniversal, out var date))
    {
        return date;
    }

    throw new FormatException($"Could not parse date. Expected yyyy-MM-dd. Value: {stringValue}");
}

若该方法为GraphQL类型解析方法，调用前将ROM转为字符串：

public override object ParseLiteral(IValue value)
{
    if (value is StringValue strValue)
    {
        return ParseDate(strValue.Value.ToString());
    }
    throw new InvalidValueException(value);
}

内容的提问来源于stack exchange，提问作者maxcimel