When IsLatest is not set on a package user profile page doesn't load

[skofman1]

For example https://www.nuget.org/profiles/kzu
The package Moq doesn't have IsLatest or IsLatestStable set.

Call stack:
System.InvalidOperationException:
at System.Linq.Enumerable.Single (System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089)
at NuGetGallery.PackageService.MergeLatestPackagesByOwner (NuGetGallery, Version=4.3.0.0, Culture=neutral, PublicKeyToken=null)
at NuGetGallery.PackageService.FindPackagesByOwner (NuGetGallery, Version=4.3.0.0, Culture=neutral, PublicKeyToken=null)
at NuGetGallery.UsersController.Profiles (NuGetGallery, Version=4.3.0.0, Culture=neutral, PublicKeyToken=null)
at lambda_method (Anonymously Hosted DynamicMethods Assembly, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null)
at System.Web.Mvc.ReflectedActionDescriptor.Execute (System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod (System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.b__39 (System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
at System.Web.Mvc.Async.AsyncResultWrapper+WrappedAsyncResult`2.CallEndDelegate (System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod (System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
at System.Web.Mvc.Async.AsyncControllerActionInvoker+AsyncInvocationWithFilters.b__3d (System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
at System.Web.Mvc.Async.AsyncControllerActionInvoker+AsyncInvocationWithFilters+<>c__DisplayClass46.b__3f (System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters (System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
at System.Web.Mvc.Async.AsyncControllerActionInvoker+<>c__DisplayClass21+<>c__DisplayClass2b.b__1c (System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)
at System.Web.Mvc.Async.AsyncControllerActionInvoker+<>c__DisplayClass21.b__1e (System.Web.Mvc, Version=5.2.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35)

Related to bug: #2514

Fixes:

1. Make the code resilient to this bug (like before, this is a regression)
2. Package reflow should recalculate IsLatest, to allow manual fix by on-call

[chenriksson]

AI outerMessage is "Sequence contains more than one matching element", indicating that multiple rows were set to IsLatest. Package at fault is IFluentInterface, where both 2.0.1 and 2.0.3 versions are set to latest.

DisplayPackage is more resilient by using FirstOrDefault, however I think we should use LastOrDefault when ordering by version ascending. Will recommend fixing the exception now by using First instead of Single, but will file a separate issue to consider LastOrDefault and to fix reflow.

[kzu]

Funny, just unlisted all other versions of IFluentInterface and now my profile shows up :)

Thanks for the investigation!

[chenriksson]

Verified in PROD that profiles load for all users with duplicate IsLatest packages. Reflow update (#4308) will allow us to correct the IsLatest state.