Add analyzer to force ConfigureAwait(false) on all awaits

We don’t add ConfigureAwait(false) to ASP.NET Core code because there is no sync context. Microsoft.Extensions.* code could execute in client apps. Not using ConfigureAwait(false) can create deadlocks when a user mixes sync with async, e.g. https://github.com/aspnet/Extensions/issues/999.

Consider introducing an analyzer to enforce ConfigureAwait(false) everywhere. A quick search of this repos source code displays many non-test awaits that don’t follow best practice.

I just had some good success using https://www.nuget.org/packages/ConfigureAwaitChecker.Analyzer/

[JamesNK]

I don’t know what Andrew ment when he said this is mostly done. I don’t think we’ve done anything 😬

Basically I think we should turn on CA2007 for all our libraries that can run outside of ASP.NET Core. We’re writing code without ConfigureAwait(false) because we’re assuming that there is never a sync context, but some of our libraries can be used in WinForms or WPF. That’s created bugs (linked in initial comment).

We should come up with a rule to apply the analyzer setting across the repo. Perhaps all projects that are:

• Published as NuGet packages
• IsAspNetCoreApp is false

Note that there are some projects where the rule will be turned off. For example, the .NET SignalR client has a different strategy to avoid sync context issues (@BrennanConroy can you confirm, its been a couple of years since I looked at the .NET SignalR client code).

tldr; DoI should pick this up

[pranavkm]

I’m going to consider this resolved based on https://github.com/dotnet/aspnetcore/pull/39946.