CSHARP-4976: MongoDB C# Driver no longer compatible with DevExpress ASP.NET Core Middleware

[sanych-sun]

No description provided.

[rstam]

Great detective work!

[rstam]

Move all this new code to a helper function (called GetOutputSerializer?) and call it from CreateDatabasePipelineDefinition also.

[rstam]

var stages = _pipeline.Stages.Select(s => (BsonDocument)s.Render());
var outputSerializer = GetOutputSerializer();
return new BsonDocumentStagePipelineDefinition<TDocument, TOutput>(stages, outputSerializer);

[rstam]

Where GetOutputSerializer is:

private IBsonSerializer<TOutput> GetOutputSerializer()
{
    var outputSerializer = _pipeline.OutputSerializer;
    var outputType = outputSerializer.ValueType;

    if (outputType == typeof(TOutput))
    {
        return (IBsonSerializer<TOutput>)outputSerializer;
    }
    else if (typeof(TOutput).IsAssignableFrom(outputType))
    {
        if (typeof(TOutput).IsNullableOf(outputType))
        {
            return (IBsonSerializer<TOutput>)NullableSerializer.Create(outputSerializer);
        }
        else
        {
            return (IBsonSerializer<TOutput>)DowncastingSerializer.Create(
                typeof(TOutput),
                outputType,
                outputSerializer);
        }
    }
    else
    {
        throw new NotSupportedException($"The type of the pipeline output is {outputType} which is not assignable to {typeof(TOutput)}.");
    }
}

Note the new exception type and message.

[rstam]

Refactor CreateDatabasePipelineDefinition to:

var stages = _pipeline.Stages.Select(s => (BsonDocument)s.Render());
var outputSerializer = GetOutputSerializer();
return new BsonDocumentStagePipelineDefinition<NoPipelineInput, TOutput>(stages, outputSerializer);

[rstam]

I think the method name should be Cast_to_object_should_work.

Because the result of the expression is being cast to object.

Similarly for other test methods.

[rstam]

Clearly separate the Arrange/Act/Assert sections of the test:

var collection = GetCollection();
var queryable1 = collection.AsQueryable();
var queryable2 = queryable1.Provider.CreateQuery<object>(queryable1.Expression);

var results = queryable2.ToList();

results.Should().HaveCount(5);

[rstam]

var collection = GetCollection();
var queryable1 = collection.AsQueryable().GroupBy(
    p => p.Type,
    (k, p) => new ProductAggregation() {Type = k, MaxPrice = p.Select(p => p.Price).Max()});
var queryable2 = queryable1.Provider.CreateQuery<object>(queryable1.Expression);

var results = queryable2.ToList();

results.Should().HaveCount(2);

[rstam]

var collection = GetCollection();
var queryable1 = collection.AsQueryable().Select(p => p.Id);
var queryable2 = queryable1.Provider.CreateQuery<object>(queryable1.Expression);

var results = queryable2.ToList();

results.Should().HaveCount(5);

[rstam]

var collection = GetCollection();
var queryable1 = collection.AsQueryable().Select(p => p.Id);
var queryable2 = queryable1.Provider.CreateQuery<int?>(queryable1.Expression);

var results = queryable2.ToList();

results.Should().HaveCount(5);

[rstam]

var collection = GetCollection();
var queryable1 = collection.AsQueryable();
var queryable2 = queryable1.Provider.CreateQuery<ProductAggregation>(queryable1.Expression);

var exception = Record.Exception(() => queryable2.ToList());

exception.Should().BeOfType<NotSupportedException>();
exception.Message.Should().Contain($"The type of the pipeline output is {typeof(DerivedProduct)} which is not assignable to {typeof(ProductAggregation)}");

[rstam]

var collection = GetCollection();
var queryable1 = collection.AsQueryable();
var queryable2 = queryable1.Provider.CreateQuery<IProduct>(queryable1.Expression);

var results = queryable2.ToList();

results.Should().HaveCount(5);

[rstam]

var collection = GetCollection();
var queryable1 = collection.AsQueryable();
var queryable2 = queryable1.Provider.CreateQuery<ProductBase>(queryable1.Expression);

var results = queryable2.ToList();

results.Should().HaveCount(5);

[rstam]

LGTM