* Add metadata to Razor
This PR introduces standard metadata to Razor. This change begins to
formalize the contract between generated code produced by Razor and
runtimes that want to load and interact with this code.
This is a step on making MVC a 'plugin' to Razor rather than the only
possible implementation. Since we're doing MSBuild work - this is the
right time to designate the current interaction between Razor and MVC as
'legacy' and move forward.
Additionally, we need the source thumbprinting to make re-compilation of
Razor a thing.
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Also I noticed that our source document doesn't expose the hash
algorithm by name. We really should have this, so I added it and
hardened the code that deals with checksums in c# generation.
- Rename `CSharpRenderingContext` => `CodeRenderingContext`.
- Rename `CSharpCodeWriter` => `CodeWriter`
- Rename `BasicWriter` => `IntermediateNodeWriter`
- Rename `...BasicWriter` => `...NodeWriter`
- Made `CodeRenderingContext` a public abstract API. Left temporary TagHelper pieces in the class since these will be removed soon.
- Moved several `CodeRenderingContext` methods into extension methods. These make use of the Items collection.
- Moved the reporting of missing code target extensions into the `ExtensionIntermediateNode`. This is the integration point of `CodeTarget`s and `CodeRenderingContext`s; therefore, it made more sense existing there.
- Left SetRenderChildren/SetRenderNode as extension methods due to how they're wired up. Aka, to create a `CodeTarget` you need a `CodeRenderingContext`... To Create a `DocumentWriter` you need a `CodeTarget`... To set the render methods on the context you need a `DocumentWriter`.
- Updated tests to utilize the new code renering constructs.
- Moved code generation testability features from `CSharpLoweringPhase` to the `CodeRenderingContext.Items`.
#1043
Ryan Nowak
Ajay Bhargav Baaskaran
N. Taylor Mullen