Nullable Reference Type for FirstOrDefaultAsync

[Vake93]

My project has nullable reference types enabled and the following code has the warning CS8619 Nullability of reference types in value of type 'Task' doesn't match target type 'Task<User?>'.

FirstOrDefaultAsync can return null and shouldn't FirstOrDefaultAsync return Task<User?> ?

Further technical details

EF Core version: 3.1.0
Database provider: Npgsql.EntityFrameworkCore.PostgreSQL 3.1.0
Target framework: .NET Core 3.1
Operating system: Windows 10
IDE: Visual Studio 2019 16.4.2

[ajcvickers]

@roji Thoughts?

[mqudsi]

Is there a master issue tracking issues relating to non-nullable reference types, or is there a document containing known issues or limitations? We're seeing some nullability confusion regarding the values passed in to linq functors or as return values from linq expressions.

[roji]

Yeah, we need to annotate our async LINQ extensions for nullability - this is part of #19007. We can close this as a duplicate of that, although there may be value in keeping this open as it's a particularly visible area of the API. Note that System.Linq has already been annotated, so we should be following that (although async may make that a bit challenging).

Is there a master issue tracking issues relating to non-nullable reference types, or is there a document containing known issues or limitations?

There's the Nullable Reference Types doc page which contains most information NRTs, I'll add a note about this current limitation.

[roji]

Submitted dotnet/EntityFramework.Docs#2022