Use Microsoft.VisualStudio.TextTemplating.Interfaces packages

[bricelam]

The Microsoft.VisualStudio.TextTemplating.Interfaces.11.0 and 10.0 packages include assemblies for netstandard2.0. They include the following interfaces:

• IDirectiveProcessor
• ITextTemplatingEngine
• ITextTemplatingEngineHost
• ITextTemplatingSession
• ITextTemplatingSessionHost

I'm not sure if there's much of an existing ecosystem around these interfaces, but if there is, taking a dependency on these packages could enable existing libraries to also work with Mono.TextTemplating.

Unfortunately, Mono.TextTemplating would have to make a few breaking changes. While TypeForwardToAttribute would mitigate most of the of breaks, there are still two that make me wonder if this would be worth it:

• This would add ProvideTemplatingAppDomain to the .NET Standard versions of ITextTemplatingEngineHost.
• This would require additional assembly references during transformation. This may be breaking because custom hosts may not currently be implementing ResolveAssemblyReference. Case in point, DummyHost in the tests currently just throws.

[bricelam]

I took an initial stab at this in bricelam:vs, but decided just to file an issue instead. 😉