Mapster.EFCore ProjectToType<T>().FirstOrDefaultAsync throwing exception

[ScarletKuro]

Very similar problem as here #566
But I don't think that "materializing the query" is an acceptable workaround:

This WORKS (without using IMapper)

var template = await query
	.ProjectToType<TemplateDto>()
	.FirstOrDefaultAsync();

This WORKS (with IMapper but FirstOrDefault)

var template = _mapper.From(query)
	.ProjectToType<TemplateDto>()
	.FirstOrDefault();

This doesn't WORK (With IMapper but FirstOrDefaultAsync)

var template = await _mapper.From(query)
	.ProjectToType<TemplateDto>()
	.FirstOrDefaultAsync();

And thows:

System.MissingMethodException
 HResult=0x80131513
 Message=Constructor on type 'Mapster.EFCore.MapsterAsyncEnumerable`1[[MessageDispatcher.Shared.Restful.Api.Dto.TemplateDto, MessageDispatcher.Shared, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]' not found.
 Source=System.Private.CoreLib
 StackTrace:
 at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)
 at System.Activator.CreateInstance(Type type, Object[] args)
 at Mapster.EFCore.MapsterQueryableProvider.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
 at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ExecuteAsync[TSource,TResult](MethodInfo operatorMethodInfo, IQueryable`1 source, Expression expression, CancellationToken cancellationToken)
 at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ExecuteAsync[TSource,TResult](MethodInfo operatorMethodInfo, IQueryable`1 source, CancellationToken cancellationToken)
 at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.FirstOrDefaultAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
 at MessageDispatcher.Services.TemplateService.<GetTemplateByNameAsync>d__7.MoveNext() in C:\Users\Dell\source\repos\MessageDispatcher\MessageDispatcher\Services\TemplateService.cs:line 64
 at MessageDispatcher.Controllers.TemplateController.<GetTemplateByName>d__3.MoveNext() in C:\Users\Dell\source\repos\MessageDispatcher\MessageDispatcher\Controllers\TemplateController.cs:line 38
 at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.TaskOfIActionResultExecutor.<Execute>d__0.MoveNext()
 at System.Runtime.CompilerServices.ValueTaskAwaiter`1.GetResult()
 at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<<InvokeActionMethodAsync>g__Logged|12_1>d.MoveNext()
 at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<<InvokeNextActionFilterAsync>g__Awaited|10_0>d.MoveNext()

The mapper itself

public class MapsterConfig : IRegister
{

 public void Register(TypeAdapterConfig config)
 {
 ...

 config.NewConfig<TemplateTranslationEntity, TemplateDto.TranslationDto>()
 .ConstructUsing(locale => new TemplateDto.TranslationDto(locale.Locale, locale.Text));

 config.NewConfig<TemplateEntity, TemplateDto>()
 .ConstructUsing(template => new TemplateDto(template.Name, template.Translations.Adapt<IReadOnlyList<TemplateDto.TranslationDto>>()));

		...
 }
}

public class TemplateTranslationEntity
{
 public long Id { get; set; }

 public long TemplateId { get; set; }

 public string Locale { get; set; } = null!;

 public string Text { get; set; } = null!;

 public TemplateEntity Template { get; set; } = null!;

 public LocaleEntity LocaleInfo { get; set; } = null!;
}

public class TemplateDto
{
 [JsonPropertyName("name")]
 public string Name { get; }

 [JsonPropertyName("translations")]
 public IReadOnlyList<TranslationDto> Translations { get; }

 [JsonConstructor]
 public TemplateDto(string name, IReadOnlyList<TranslationDto> translations)
 {
 Name = name;
 Translations = translations;
 }

 public class TranslationDto
 {
 [JsonPropertyName("languageCode")]
 public string LanguageCode { get; }

 [JsonPropertyName("content")]
 public string Content { get; }

 [JsonConstructor]
 public TranslationDto(string languageCode, string content)
 {
 LanguageCode = languageCode;
 Content = content;
 }
 }
}

Why does await query.ProjectToType is different from _mapper.From(query).ProjectToType?

NB! Switching from constructor to property mapping gave the same error.

Additional info:

.NET 9.0
Mapster 7.4.0
Mapster.EFCore 5.1.1
Mapster.DependencyInjection 1.0.1

[ScarletKuro]

I don't think it should even wrap in MapsterAsyncEnumerable for FirstOrDefaultAsync here?
Shouldn't it be something like

public TResult ExecuteAsync<TResult>(Expression expression, CancellationToken cancellationToken = default)
{
 var enumerable = ((IAsyncQueryProvider)_provider).ExecuteAsync<TResult>(expression, cancellationToken);
 var enumerableType = typeof(TResult);
+ if (!IsAsyncEnumerableType(enumerableType))
+ {
+	 return enumerable;
+ }
 var elementType = enumerableType.GetGenericArguments()[0];
 ...
}

+private static bool IsAsyncEnumerableType(Type type)
+{
+	return type.GetInterfaces()
+		.Any(i => i.IsGenericType && i.GetGenericTypeDefinition() == typeof(IAsyncEnumerable<>));
+}

in MapsterQueryable.cs

At least it fixes the problem, but I didn't test it properly yet.

[DocSvartz]

@ScarletKuro Yes, The problem here is that FirstOrDefaultAsync() doesn't return an Enumerator, it return Task
But for some reason, it's handled by the Enumerator code.

[ScarletKuro]

Made a PR #821 with a test. Hopefully this can be merged soon and released so I don't need to drag a custom version.

[DocSvartz]

@ScarletKuro Great job! 👍

[ScarletKuro]

Guess this can be closed if #823 was merged in the main?

[DocSvartz]

@ScarletKuro Yes, it is will be merged.