ODL library allows you to write a nested resource as the value for a primitive property

[gathogojr]

ODL library allows you to write a nested resource as the value for a primitive property

Assemblies affected

• Microsoft.OData.Core 7.x
• Microsoft.OData.Core 8.x

Reproduce steps

Consider the following data models, where Customer is a navigation property:

public class Order
{
    public int Id { get; set; }
    public decimal Amount { get; set; }
    public Customer Customer { get; set; }
}

public class Customer
{
    public int Id { get; set; }
    public string Name { get; set; }
}

The following code for writing an OData payload executes okay but produces an invalid output - the value for the Amount primitive property is a nested Customer resource/object:

var modelBuilder = new ODataConventionModelBuilder();
modelBuilder.EntitySet<Order>("Orders");
modelBuilder.EntitySet<Customer>("Customers");

var model = modelBuilder.GetEdmModel();

var orderEntityType = model.SchemaElements.First(d => d.Name == "Order") as IEdmEntityType;
var ordersEntitySet = model.EntityContainer.FindEntitySet("Orders");

var messageWriterSettings = new ODataMessageWriterSettings
{
    EnableMessageStreamDisposal = false,
    Version = ODataVersion.V4,
    ODataUri = new ODataUri { ServiceRoot = new Uri("http://tempuri.org") }
};

var tempStream = new MemoryStream();

IODataResponseMessage asyncResponseMessage = new InMemoryMessage { Stream = tempStream };

await using (var messageWriter = new ODataMessageWriter(asyncResponseMessage, messageWriterSettings, model))
{
    var orderResource = new ODataResource
    {
        TypeName = typeof(Order).FullName,
        Id = new Uri("http://tempuri.org/Orders(1)"),
        Properties = new List<ODataProperty>
        {
            new ODataProperty { Name = "Id", Value = 1 }
        }
    };

    var customerResource = new ODataResource
    {
        TypeName = typeof(Customer).FullName,
        Id = new Uri("http://tempuri.org/Customers(1)"),
        Properties = new List<ODataProperty>
        {
            new ODataProperty { Name = "Id", Value = 1 },
            new ODataProperty { Name = "Name", Value = "Sue" }
        }
    };

    var customerNestedResourceInfo = new ODataNestedResourceInfo
    {
        Name = "Amount", // Not a complex, complex collection or navigation property
        IsCollection = false,
        Url = new Uri("http://tempuri.org/Orders(1)/Amount")
    };

    var resourceWriter = await messageWriter.CreateODataResourceWriterAsync(ordersEntitySet, orderEntityType);

    await resourceWriter.WriteStartAsync(orderResource);
    await resourceWriter.WriteStartAsync(customerNestedResourceInfo);
    await resourceWriter.WriteStartAsync(customerResource);
    await resourceWriter.WriteEndAsync();
    await resourceWriter.WriteEndAsync();
    await resourceWriter.WriteEndAsync();

    tempStream.Position = 0;
    var result = await new StreamReader(tempStream).ReadToEndAsync();

    // result: 
    // {
    //     "@odata.context":"http://tempuri.org/$metadata#Orders/$entity",
    //     "@odata.id":"http://tempuri.org/Orders(1)",
    //     "Id":1,
    //     "Amount":{"@odata.id":"http://tempuri.org/Customers(1)","Id":1,"Name":"Sue"}
    // }
}

Even worse, the library allows you to write the primitive property both with a primitive value as well as a nested resource resulting into a duplicate property, i.e., if you include the Amount property in the Properties collection as follows,

    var orderResource = new ODataResource
    {
        TypeName = typeof(Order).FullName,
        Id = new Uri("http://tempuri.org/Orders(1)"),
        Properties = new List<ODataProperty>
        {
            new ODataProperty { Name = "Id", Value = 1 },
            new ODataProperty { Name = "Amount", Value = 130 }
        }
    };

Below is how the output payload will look like:

{
    "@odata.context":"http://tempuri.org/$metadata#Orders/$entity",
    "@odata.id":"http://tempuri.org/Orders(1)",
    "Id":1,
    "Amount":130,
    "Amount":{"@odata.id":"http://tempuri.org/Customers(1)","Id":1,"Name":"Sue"}
}

Expected result

The library should validate the property assigned to the Name property of an ODataNestedResourceInfo is either a complex or complex collection or navigation property.

Actual result

The library does not validate the property assigned to the Name property of an ODataNestedResourceInfo is either a complex or complex collection or navigation property.

Additional detail

Here's the definition of the InMemoryMessage type:

internal class InMemoryMessage : IODataResponseMessage, IODataResponseMessageAsync, IODataRequestMessage, IODataRequestMessageAsync        
{
    private readonly Dictionary<string, string> headers;

    public InMemoryMessage()
    {
        headers = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
    }

    public IEnumerable<KeyValuePair<string, string>> Headers
    {
        get { return this.headers; }
    }

    public int StatusCode { get; set; }

    public Uri Url { get; set; }

    public string Method { get; set; }

    public Stream Stream { get; set; }

    public string GetHeader(string headerName)
    {
        return this.headers.TryGetValue(headerName, out string headerValue) ? headerValue : null;
    }

    public void SetHeader(string headerName, string headerValue)
    {
        headers[headerName] = headerValue;
    }

    public Stream GetStream()
    {
        return this.Stream;
    }

    public Task<Stream> GetStreamAsync()
    {
        TaskCompletionSource<Stream> taskCompletionSource = new TaskCompletionSource<Stream>();
        taskCompletionSource.SetResult(this.Stream);
        return taskCompletionSource.Task;
    }
}