ROSLYN

.NET Compiler Platform

Hi. I'm ns

github.com/vlova/RoslynSlides

• github.com/dotnet/roslyn
• source.roslyn.io/
• github.com/dotnet/roslyn/tree/master/docs

Links

Roslyn

• compiler/scripting API
• syntax analysis & transformation API
• semantic analysis API
• workspace API

You can use it for

• Source explorers (like source.roslyn.io) or compilers

• Diagnostics and refactorings

• Style checking tools

• Project-specific solution wide analysis and refactorings (when regexps doesn't helps)

• Integration to editors (like omnisharp.net)

• Live coding (like comealive.io)

• Or smth crazy

But here are problems

• fucking ugly documentation. It's not like tutorials about MVC 4 or Rails 
• a lot of nice stuff isn't covered with documentation or tutorials
• a lot of good tutorials doesn't exists or are deprecated
• source code of roslyn & existing tools is your best documentation

And here are more problems

• API IS CODE GENERATED. 

• API is focused on speed & thread safety, so some things are hard to code

• AST of C# language is very complex and monsterous. 
• some API aren't language-specific (e.g. should support both VB and C#) 
• hard debugging

And that's not all

• it's more easier to concatenate strings and parse them than use syntax creating API

• it's more easier to use regexes to perform easy solution-wide refactorings

But it's a very nice and powerful tool, ok?

You should believe me, it's cool ;-)

Why it's cool?

• It works
• It works fast
• You can do amazing things
• Documentation and tutorials aren't so ugly as I described ;-)

Key stuff

• Document consists of some metadata & SyntaxTree
• SyntaxNodes are mapped directly to text
• Each SyntaxNode is immutable
• Nodes can be rewritten and transformed
• You can create SyntaxNode with SyntaxFactory

Key stuff

• Each node contains both AST and whitespace-trash

• Whitespace-trash is important too :-)
• But you can ask Roslyn to automatically reformart code

Key stuff

• Document also has a concept of SemanticModel

• SemanticModel is IntelliSense API

• Some methods of SemanticModel has speculative overloads

Key stuff

There a lot of nice classes providing abstractions over SyntaxTrees & SemanticModels 

Let's start

• Visual Studio 2015
• .NET Compiler Platform SDK 
• NuGet packages Microsoft.CodeAnalysis.*

T : CodeRefactoringProvider

• It's called only when user press Ctrl+.
• When provider is called it's got a span of user text
• Then your code can think if it can provide something for user
• Visual Studio tries to show & apply changes (if user chooses your CodeAction)

Sample: AddArgumentNameProvider

T : DiagnosticAnalyzer

• On init you should register event handlers
• Event handlers can be called twice or more for the same part of code
• In event handler you can report that code has problems
• Reporting doesn't means fixing
• Yes, you can just say 'you code is bullshit' :-)

Sample: UsageOfClassInsteadOfInterfaceAnalyzer

T : CodeFixProvider

• Subscribes to specified diagnostics
• Still called when user press Ctrl+.
• But supports bulk codefixes
• Can get some data from diagnostic provider

Sample: UsageOfClassInsteadOfInterfaceCodeFixProvider

Console analyzers

Subtitle

using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.MSBuild;

var workspace = MSBuildWorkspace.Create();
var solutionInfo = SolutionInfo.Create(
    SolutionId.CreateNewId(), 
    VersionStamp.Create(), 
    slnPath);
var solution = await workspace
    .OpenSolutionAsync(slnPath);
var documents = solution.Projects
    .SelectMany(p => p.Documents);

Useful API 

SyntaxFactory

Low level creation of SyntaxNodes

Microsoft.CodeAnalysis.CSharp

SyntaxGenerator

Microsoft.CodeAnalysis.Editing

Language-agnostic high-level beautiful API

DocumentEditor

Provides imperative-style for manipulating documents.  

Microsoft.CodeAnalysis.Editing

And another imperative stuff

• SyntaxEditor

• SymbolEditor

• SolutionEditor

SymbolFinder

Microsoft.CodeAnalysis.FindSymbols

Extensions of

Semantic Model

Renamer

Microsoft.CodeAnalysis.Rename

Formatter

Microsoft.CodeAnalysis.Formatting

Simplifier

Microsoft.CodeAnalysis.Simplification

WarningAnnotation

Microsoft.CodeAnalysis.CodeActions

ConflictAnnotation

RenameAnnotation

Classifier

Microsoft.CodeAnalysis.Classification

Syntax Highlight

http://sergeyteplyakov.blogspot.com/2015/03/syntax-highlighter-roslyn.html

Recommender

Microsoft.CodeAnalysis.FindSymbols

C#-specific autocomplete

Questions?