Inferring `FromServices` optionality based on nullability information

[brunolins16]

Current design

Currently, when binding FromServices always is called the ServiceProviderServiceExtensions.GetRequiredService (that throws an InvalidOperationException when the service is not found)

aspnetcore/src/Mvc/Mvc.Core/src/ModelBinding/Binders/ServicesModelBinder.cs

Line 26 in 6bbd520

var model = requestServices.GetRequiredService(bindingContext.ModelType);

Proposed Change

The proposal is following the same approach apply in Minimal APIs, that basically evaluates the default value and nullability context to decide if the parameter is optional or not and call the ServiceProviderServiceExtensions.GetService instead when the parameter is optional.

aspnetcore/src/Http/Http.Extensions/src/RequestDelegateFactory.cs

Line 866 in 6bbd520

private static Expression BindParameterFromService(ParameterInfo parameter, FactoryContext factoryContext)

Thanks for contacting us.

We're moving this issue to the .NET 7 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.