Roslyn Cookbook

Manish Vasani

• Publisher: Packt Publishing
• Year: 2017
• ISBN:
  9781787288522
• Edition: 1
• Topic: Informatique
• Subtopic: Programmation en C#

Use Roslyn as a service to write powerful extensions and tools and use them in Visual Studio to improve code quality and maintain your source code more effectively.About This Book• Use Roslyn extensions and tools in Visual Studio to enforce "house rules" on code and fix security and performance vulnerabilities in your code.• Write Roslyn extensions using the Roslyn service API to help developers enforce conventions and design idioms.• Improve developer productivity by using Roslyn-based agile development features in Visual Studio, such as live unit testing, C# interactive and scripting.• Contribute to the C# language and compiler tool chain to analyze and edit code.Who This Book Is For.NET Developers and architects, who are interested in taking full advantage of the Roslyn based extensions and tools to improve the development processes, will find this book useful. Roslyn contributors, i.e. the producers and C# community developers, will also find this book usefulWhat You Will Learn• Write extensions to analyze source code and report warnings and errors.• Edit C# source code to fix compiler/analyzer diagnostics or refactor source code.• Improve code maintenance and readability by using analyzers and code fixes.• Catch security and performance issues by using PUMA scan analyzers and FxCop analyzers.• Perform Live Unit tests in Visual Studio.• Use C# interactive and scripting in Visual Studio.• Design a new C# language feature and implement various compiler phases for a new language feature.• Write command line tools to analyze and edit C# code.In DetailOpen-sourcing the C# and Visual Basic compilers is one of the most appreciated things by the.NET community, especially as it exposes rich code analysis APIs to analyze and edit code. If you want to use Roslyn API to write powerful extensions and contribute to the C# developer tool chain, then this book is for you. Additionally, if you are just a.NET developer and want to use this rich Roslyn-based functionality in Visual Studio to improve the code quality and maintenance of your code base, then this book is also for you.This book is divided into the following broad modules: 1. Writing and consuming analyzers/fixers (Chapters 1 - 5): You will learn to write different categories of Roslyn analyzers and harness and configure analyzers in your C# projects to catch quality, security and performance issues. Moving ahead, you will learn how to improve code maintenance and readability by using code fixes and refactorings and also learn how to write them.2. Using Roslyn-based agile development features (Chapters 6 and 7): You will learn how to improve developer productivity in Visual Studio by using features such as live unit testing, C# interactive and scripting.3. Contributing to the C# language and compiler tool chain (Chapters 8 - 10): You will see the power of open-sourcing the Roslyn compiler via the simple steps this book provides; thus, you will contribute a completely new C# language feature and implement it in the Roslyn compiler codebase. Finally, you will write simple command line tools based on the Roslyn service API to analyze and edit C# code.Style and approachThis book takes a recipe-based approach, teaching you how to perform various hacks with the Compiler API in your hands.

Writing Diagnostic Analyzers

In this chapter, we will cover the following recipes:

• Creating, debugging, and executing an analyzer project in Visual Studio
• Creating a symbol analyzer to report issues about symbol declarations
• Creating a syntax node analyzer to report issues about language syntax
• Creating a syntax tree analyzer to analyze source file and report syntax issues
• Creating a method body analyzer to analyze whole method and report issues
• Creating a compilation analyzer to analyze whole compilation and report issues
• Writing unit tests for an analyzer project
• Publishing the NuGet package and VSIX for an analyzer project

Introduction

Diagnostic analyzers are extensions to the Roslyn C# compiler and Visual Studio IDE to analyze user code and report diagnostics. Users will see these diagnostics in the error list after building the project from Visual Studio, and even when building the project on the command line. They will also see the diagnostics live while editing the source code in the Visual Studio IDE. Analyzers can report diagnostics to enforce specific code styles, improve code quality and maintenance, recommend design guidelines, or even report very domain-specific issues which cannot be covered by the core compiler. This chapter enables C# developers to write, debug, test, and publish analyzers that perform different kinds of analyses.

If you are not familiar with the Roslyn's architecture and API layers, it is recommended that, before reading this chapter further, you read the Preface of this book to gain a basic understanding of Roslyn APIs.

Diagnostic analyzers are built on top of the Roslyn's CodeAnalysis/Compiler layer API. Analyzers can analyze specific code units, such as a symbol, syntax node, code block, compilation, and so on, by registering one or more analyzer actions. The compiler layer makes a callback into the analyzer whenever it compiles a code unit of interest. The analyzer can report diagnostics on code units, which are added to the list of the compiler diagnostics and reported back to the end user.

Analyzers can be broadly categorized into the following two buckets based on the kind of analysis performed:

• Stateless analyzers: Analyzers that report diagnostics about a specific code unit by registering one or more analyzer actions that:
  • Do not require maintaining any state across analyzer actions.
  • Independent of the order of execution of individual analyzer actions.

For example, an analyzer that looks at every single class declaration independently and reports issues about the declaration is a stateless analyzer. We will show you how to write a stateless symbol, syntax node, and syntax tree analyzer, later in this chapter.

• Stateful analyzers: Analyzers that report diagnostics about a specific code unit, but in the context of an enclosing code unit, such as a code block or a compilation. These are more complicated analyzers that require powerful and wider analysis, hence, need careful design to achieve efficient analyzer execution without memory leaks. These analyzers require at least one of the following kinds of state manipulation for analysis:
  • Access to immutable state objects for the enclosing code unit, such as a compilation or the code block. For example, access to certain well-known types defined in a compilation.
  • Perform analysis over the enclosing code unit, with mutable state defined and initialized in a start action for the enclosing code unit, intermediate nested actions that access and/or update this state, and an end action to report diagnostic on the individual code units.

For example, an analyzer that looks at all class declarations in a compilation, gathering and updating a common state when analyzing each class declaration, and then finally, after it has analyzed all declarations, reports issues about those declarations is a stateful analyzer. We will show you how to write a stateful method body and compilation analyzer in this chapter.

By default, analyzers can analyze and report diagnostics on source files in a project. However, we can also write an analyzer that analyzes additional files, that is, non-source text files included in the project, and also report diagnostics in additional files. Non-source files could be files, such as Web.config files in a web project, cshtml files in a Razor project, XAML files in a WPF project, and so on. You can read more about how to write and consume additional file analyzers at https://github.com/dotnet/roslyn/blob/master/docs/analyzers/Using%20Additional%20Files.md.

Creating, debugging, and executing an analyzer project in Visual Studio

We will show you how to install the .NET Compiler Platform SDK, create an analyzer project from a template, and then debug and execute the default analyzer.

The analyzer project that you create in this recipe can be used in the subsequent recipes in this chapter to add new analyzers and write unit tests.

Getting ready

You will need to have Visual Studio 2017 installed on your machine to execute the recipes in this chapter. You can install a free community version of Visual Studio 2017 from https://www.visualstudio.com/thank-you-downloading-visual-studio/?sku=Community&rel=15.

How to do it...

1. Start Visual Studio and click on File | New | Project.
2. Search for Analyzer templates in the textbox at the top right corner of the New Project dialog, select Download the .NET Compiler Platform SDK, and click on OK:

3. The new project will have an index.html file opened by default. Click on Download .NET Compiler Platform SDK Templates >> button to install the analyzer SDK templates.

4. In the subsequ...