Fix untestable extension methods

[davidfowl]

• https://github.com/aspnet/HttpAbstractions/blob/dev/src/Microsoft.AspNetCore.Http.Extensions/SendFileResponseExtensions.cs
• https://github.com/aspnet/HttpAbstractions/blob/dev/src/Microsoft.AspNetCore.Http.Extensions/FormFileExtensions.cs

These methods demand that files be on disk. What makes it worse is that these are extension methods so they cannot be stubbed.

Maybe we should make these virtual on HttpResponse and IFormFile (interface method).

/cc @Eilon @Tratcher @lodejard

[glennc]

If we are going to do this we should do it now, moving methods around after RC2 should be avoided.

[davidfowl]

another alternative might be to add an overload that takes IFileInfo

[davidfowl]

Ughm IFileInfo is read only...

[khellang]

another alternative might be to add an overload that takes IFileInfo

Add an overload where? For SendFile?

What about the FormFileExtensions? Promote them to IFormFile?

[davidfowl]

@khellang Those are the 2 options. Either promote to interface or use some overload that takes a writable file abstraction.

[davidfowl]

For SendFile, we should allow passing IFileInfo

[muratg]

Moving this to Backlog as we will be in RC2 ask mode very soon. If you feel strongly about this issue, please ping me.

[lodejard]

On the Form file extensions, why not Task SaveAsync(Stream target)?

The IFileInfo for SendFile is good though - because if it's has a non-null-or-empty PhysicalFilePath some servers can accelerate that.

[khellang]

I think Task SaveAsync(Stream target) makes sense, then the Task SaveAsync(string path) overloads could be extension methods again 😛