Fix argument null exception during projection

[uffelauesen]

Issues

This pull request fixes #3037.

Description

Fixes issue in ProjectionValueForPath() when linkEntry.Properties is null bypassing call to OfType().

Checklist (Uncheck if it is not completed)

• Test cases added
• Build and test with one-click build and test script passed

Additional work necessary

Regression introduced in ODL Client 8.0.0-rc.1

[habbes]

Thanks for the catch. This must be due to change from ODataProperty to ODataPropertyInfo. I'm surprised no tests failed because of this. But most of client query tests are in E2E tests which are still being ported over. @ElizabethOkerio have we ported any E2E tests that perform a projection?

[habbes]

The issue was introduced by this PR: #2916

The root issue is that ODataResource.Properties and MaterializerEntry.Properties could be null. So may have other places that could break. We should consider adding the null check here as well: https://github.com/OData/odata.net/pull/2916/files#diff-a39b2ec2693141c7a1e515c2b9ca95fb0fd0b3eacc903b92e61a048d07738fe0R253

[habbes]

Thanks @gathogojr for adding the tests

[gathogojr]

More details from the investigation:

var serviceRoot = new Uri("http://localhost:5205");
var ctx = new Container(serviceRoot);

var query1 = from people in ctx.People
            where people.Spouse == null
            select new Person
            {
                Id = people.Id,
                Spouse = people.Spouse
            };
// OData URL: http://localhost:5205/People?$filter=Spouse eq null&$expand=Spouse&$select=Id
var results1 = query1.ToList(); // Throws exception

var query2 = ctx.CreateQuery<Person>("People").Where(p1 => p1.Spouse == null).Select(p2 => new { p2.Id, p2.Spouse });
// OData URL: http://localhost:5205/People?$filter=Spouse eq null&$expand=Spouse&$select=Id
var results2 = query2.ToList(); // Throws exception

var query3 = ctx.People.AddQueryOption("$filter", "Spouse eq null").AddQueryOption("$expand", "Spouse").AddQueryOption("$select", "Id");
// OData URL: http://localhost:5205/People?$expand=Spouse&$filter=Spouse eq null&$select=Id
var results3 = query3.ToList(); // No exception thrown

var query4 = ctx.Execute<Person>(new Uri("http://localhost:5205/People?$expand=Spouse&$filter=Spouse eq null&$select=Id"));
// OData URL: http://localhost:5205/People?$expand=Spouse&$filter=Spouse eq null&$select=Id
var results4 = query4.ToList(); // No exception thrown

var query5 = ctx.Execute<Person>(new Uri("http://localhost:5205/People?$filter=Spouse eq null&$expand=Spouse&$select=Id"));
// OData URL: http://localhost:5205/People?$filter=Spouse eq null&$expand=Spouse&$select=Id
var results5 = query5.ToList(); // No exception thrown! Yet the OData URL mirrors that of the first two query expressions. Projection seems to be where the issue is