Change `Service` to not longer implement `IIceObjectService`

[bentoi]

I propose to add IceService and get rid of the Service dependency on IIceObjectService.

I would also rename AsAsync to IceAsAsync since this method depends on Ice's ice_isA operation which might not be implemented by the IceRpc service.

[bernardnormier]

Thanks to the Ice demos, the vast majority of Ice client applications use checkedCast.

As a result, if you reimplement an Ice server with IceRPC, your services need to implement ice_isA for interop. How do you make this happen if Service no longer implements IIceObjectService?

[bentoi]

Your service would extend IceService if clients need checkedCast.

[bernardnormier]

What about the generated code?

We'd still generate [IceRpc.Slice.TypeId(...)] on all interfaces (including Slice2 interfaces) "just in case" you decide to implement XxxService with IceService?

[bernardnormier]

Actually we also use [IceRpc.Slice.TypeId(...)] for default path support.

[bentoi]

We also support GetSliceTypeId, GetAllSliceTypeIds extension methods. Can't an IceRpc service use them to implement a custom IsA operation even if it's not really a good idea?

[bernardnormier]

I propose to add IceService

My preference is to have a single Service base class--and soon replace it with a Service attribute: see #2663.

If this single Service base class / attribute can be reasonably easily "configured" to implement or not implement automatically IIObjectService, that's fine with me. I don't see a trivial solution. In particular, if you write:

internal class MyService : Service, IIObjectService
{
    ...
}

MyService needs to implement IIObjectService's methods.

[bernardnormier]

Can't an IceRpc service use them to implement a custom IsA operation even if it's not really a good idea?

I don't understand your suggestion here.

Keep in mind that Service already uses GetAllSliceTypeIds to implement ice_isA and ice_ids:
https://github.com/zeroc-ice/icerpc-csharp/blob/b17fb3c24a77a07f2d647bb9aefdf495b81af6ec/src/IceRpc/Slice/Service.cs#L72

[bentoi]

MyService needs to implement IIObjectService's methods.

See my PR. This proposal is to add an IceObjectService base classe that implements IIceObjectService operations.

[bernardnormier]

You did not articulate a rationale for this proposal.

The way I see it: with IceRPC C#, a Slice IceRPC service always automatically implements Slice interface Ice::IceObject. The user does not need to think about it, it helps with interop with Ice, and there is no downside.

It's not like implementing these extra 3 operations is costly or risks some clash with application code.

[bentoi]

The rational is to remove dependencies from the Slice engine on Ice definitions.

I don't think it's good to have a dependency on IceRpc.Ice types from IceRpc.Slice public types. I also don't think it's a good idea to have IceRpc.Service implement methods that we don't recommend using in modern IceRpc applications.

Ice servers that are ported to IceRpc and still want to support these methods for Ice clients should extend IceObjectService instead.