使用表达式在泛型方法中模拟泛型 return 类型

Question

我有以下带有泛型方法的接口。

public interface IRepository {
  Task<TResult> GetByIdAsync<TResult>(
    int id,
    Expression<Func<Entity, TResult>> expression,
    TResult defaultValue = default);
}

部分代码表达returns元组和匿名类型。

例子

var _repository = ServiceProvider.GetRequiredService<IRepository>();

var data = await _repository.GetByIdAsync(id, pr => Tuple.Create(pr, pr.SelfRefObject));
var data = await _repository.GetByIdAsync(id, pr => new { pr.SelfRefObjectId });

是否可以模拟该方法，使其 returns 指定具有上述类型的值？

例子

var _repositoryMock = new Mock<IRepository>();

var anonymousReturnValue = new { SelfRefObjectId = 1 };

 _repositoryMock
  .Setup(pr => pr.GetByIdAsync(
    entityId,
    pr => new { pr.SelfRefObjectId },
    default))
  .ReturnsAsync(anonymousReturnValue)
  .Verifiable();

var tupleReturnValue = Tuple.Create(new Entity(), new Entity());

 _repositoryMock
  .Setup(pr => pr.GetByIdAsync(
    entityId,
    pr => Tuple.Create(pr, pr.SelfRefObject),
    default))
  .ReturnsAsync(tupleReturnValue)
  .Verifiable();

提前致谢。

Answer 1

简而言之：据我所知，你不能这样做。

有两种非常有用的助手类型：It.IsAnyType 和 It.IsSubType<T>。

在设置阶段，您可以使用它们来表明您的函数接受任何内容：

_repositoryMock
    .Setup(repo => repo.GetByIdAsync(
        It.IsAny<int>(), 
        It.IsAny<Expression<Func<Entity, It.IsAnyType>>>(), 
        It.IsAny<It.IsAnyType>()))
    .Verifiable();

或者只接受匿名类型或元组:

_repositoryMock
    .Setup(repo => repo.GetByIdAsync(
        It.IsAny<int>(), 
        It.Is<Expression<Func<Entity, It.IsAnyType>>>((o, type) => type.IsAnonymousType()), 
        It.Is<It.IsAnyType>((o, type) => type.IsAnonymousType())))
    .Verifiable();

_repositoryMock
    .Setup(repo => repo.GetByIdAsync(
        It.IsAny<int>(), 
        It.Is<Expression<Func<Entity, It.IsAnyType>>>((o, type) => type.IsTuple()), 
        It.Is<It.IsAnyType>((o, type) => type.IsTuple())))
    .Verifiable();

辅助方法：

public static class TypeExtension
{
    public static bool IsAnonymousType(this Type type)
    {
        var hasCompilerGeneratedAttribute = type.GetCustomAttributes(typeof(CompilerGeneratedAttribute), false).Any();
        var nameContainsAnonymousType = type.FullName != null && type.FullName.Contains("AnonymousType");
        return hasCompilerGeneratedAttribute && nameContainsAnonymousType;
    }

    public static bool IsTuple(this Type type)
    {
        if (!type.IsGenericType) return false;
        var openType = type.GetGenericTypeDefinition();
        return openType == typeof(Tuple<>) || openType == typeof(Tuple<,>) 
               || openType == typeof(ValueTuple<>) || openType == typeof(ValueTuple<,>);
    }
}

当您需要指定 Return/ReturnAsync 部分时，问题就来了。

_repositoryMock
    .Setup(repo => repo.GetByIdAsync(
        It.IsAny<int>(), 
        It.Is<Expression<Func<Entity, It.IsAnyType>>>((o, type) => type.IsTuple()), 
        It.Is<It.IsAnyType>((o, type) => type.IsTuple())))
    .Returns(valueFunction: () => Task.FromResult(tupleReturnValue));

它不会编译，因为它无法将 Tuple<Entity, Entity> 转换为 Mock.It.IsAnyType

Severity Code Description Project File Line Suppression State Error CS0029 Cannot implicitly convert type 'System.Threading.Tasks.Task<System.Tuple<anonym.Entity, anonym.Entity>>' to 'System.Threading.Tasks.Task<Moq.It.IsAnyType>'

即使相关 github issue 已关闭，类型解析器似乎也不起作用。

Alternative approach 可以利用 DefaultValueProvider.

使用表达式在泛型方法中模拟泛型 return 类型

Mocking generic return type in generic method with a expression

c#

generics

moq