Landing Roslyn
From an operational point of view we can identify the following stages during compilation execution pipeline
For each of them we are going to introduce corresponding Compilation API which provides an operational object model with the information corresponding to each stage, something similar to :
From a high perspective, we can summarize the compilation pipeline in the following way: ·
- At the first stage, the Parser will get the user code and it will be converted in a collection of hierarchical tokens that will be part of special structure called SyntaxTree. The compilation process starts by creating a sequence of position-based tokens (spans) for each element in code, these tokens can be mapped to different elements like identifiers
- Next step involves symbols and metadata imports; the execution looks for all the compilation references and opens up them in order to know types that are defined in metadata containers. As part of this process all symbols will be identified
- Next phase will be Binding in which all identifiers will be assigned to the right symbols
- Finally, IL Emitter will be the responsible for creating the bytecode (IL instructions) and packed them into an assembly
Basis on these Compilation APIs a rich collection of language services can be created and integrated into Visual Studio; by using the Syntax Tree API we can provide code formatting, syntax highlighting, provide colour to special keywords, outlining, etc…
Symbols APIs allow us to find the exact locations of identifiers for providing functionality like “Navigate To” and Object Browsing (for instance, when we click F2 in Visual Studio) which show us hierarchical views for namespaces, types, members, etc… ;
Binding and Flow Analysis API is the responsible for providing a lot of languages features like : “Go To Definition”, “Rename”, “Find All References”, ”Extract Method”, etc..
Emit API is the responsible of language services like “Edit and Continue”, expression evaluator used in Visual Studio Immediate Window
Roslyn APIs
In addition to Compiler APIs, Roslyn provides Diagnostic APIs, Workspace APIs and Scripting APIs, let´s detail each of them briefly:
Diagnostic APIs
Diagnostic APIs provides an object model for controlling all aspects related with informational diagnosis of syntax and semantic code analysis; this allows developers to create custom analyzers which can be easily integrated with tools like Visual Studio for just-in time information at editors: things like red squiggles, code fixes. Refactorings are also cover by these APIs, which need a more ample context than local code fixes for performing operations
Workspace APIs
Workspace API exposes an object model for modelling items like solutions, projects and files for providing coverage to general operations like Formatting, Find All Reference and Code Generation (for instance when we click “Add” new file, or when we rename a file), etc…
According to Roslyn main page, Workspace API is the basis for doing code analysis over entire solutions. It helps us in organizing all the information about the projects in a solution into centralized object model, offering you direct access to the compiler layer object models without needing to parse files, configure options or manage project to project dependencies
Getting Ready for Use
At time of this writing I´m using VS2015 for samples, so in order to use Roslyn (and according to Roslyn site) we need to:
- Install Visual Studio 2015 SDK
- Install SDK Templates VSIX package
- Install Syntax Visualizer VSIX package
Or we can get the last version of NuGet Roslyn Compiler Package, by running Install-Package Microsoft.CodeAnalysis –Pre at Nuget Package manager console. VS2015 is the first visual studio version in which we can use Roslyn for creating VS extensions. We can also use the Nuget Manager IDE directly
If we run a console application and run “where csc.exe” command, we will see that two instances of C# compiler are found :
The first one corresponds to Roslyn compiler and the second one to the previous version of C# compiler, as we can see below
Now we have seen the basics of Roslyn let´s deep into more details and explore some implementations
That´s all by now
See you on the road !