System.Net.Http.HttpClient add virtual to SendAsync overloads to allow performant and testable code

[lennybacon]

The HttpClient supports performance optimizations due to its overload of SendAsync with the HttpCompletionOption argument.

If I want to write testable code I inject a mock or dummy deriving from HttpClient. The base class (HttpMessageInvoker) defines SendAsync(HttpRequestMessage, CancellationToken) as virtual, so it can be overridden in the mock or dummy.

The overloads of the SendAsync method in HttpClient are not specified as virtual, so currently one has to decide: Write testable or performant code.

It would be great if the overloads of the SendAsync woyuld be declared virtual.

[scalablecory]

Mocking the invoker should generally be sufficient.

The HttpCompletionOption overloads are a very thin wrapper around the message invoker. They only specify if, after calling HttpMessageInvoker.SendAsync(), it should also call HttpContent.LoadIntoBufferAsync().

This has already been discussed at length in dotnet/runtime#14535, with the decision being to not make these virtual. If you believe there's more to add to that conversation, please open a new issue there on the dotnet/runtime repo.