Return values of SingleOrDefaultAsync incorrect when nullable reference types are enabled

[dannyBies]

In my project I have nullable reference types enabled.
<Nullable>enable</Nullable>

I believe the return type is incorrect for the following methods in EntityFrameworkQueryableExtensions.cs

• FirstOrDefaultAsync
• LastOrDefaultAsync
• SingleOrDefaultAsync

I believe those methods should use the [return: MaybeNull] attribute just like equivalent System.Linq methods do.

Steps to reproduce

I would expect a build error at foundInvite.Expired as this could return null.

Further technical details

EF Core version: 5.0.0-preview.7.20365.15
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET5
Operating system: Windows 10
IDE: 16.7.0 Preview 5.0

[roji]

Simply adding [MaybeNull] isn't the right solution here for the async methods, see #21794 (comment).

[roji]

Duplicate of #19007

[roji]

@dannyBies T? is being added for C# 9, which would be the correct annotation for this (as it allows annotating the nested generic type parameter): dotnet/roslyn#45993

[dannyBies]

That's great, thanks for letting me know! Any idea when this will be usable in this project? I can make the necessary changes once T? is available here.

[roji]

We're definitely not going to be doing any nullability annotation work for the upcoming 5.0 release (which is being stabilized), but I really hope we have time to that for 6.0. Track #19007 to know what's going on.