Roslyn Analyzers

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What is Roslyn?

Roslyn is the compiler platform for .NET. It consists of the compiler itself and a powerful set of APIs to interact with the compiler. The Roslyn platform is hosted at github.com/dotnet/roslyn.

What are Roslyn Analyzers?

Roslyn analyzers analyze your code for style, quality and maintainability, design and other issues. The documentation for Roslyn Analyzers can be found at learn.microsoft.com/dotnet/fundamentals/code-analysis/overview.

Microsoft created a set of analyzers called Microsoft.CodeAnalysis.NetAnalyzers that contains the most important "FxCop" rules from static code analysis, converted to Roslyn analyzers, in addition to more analyzers. These analyzers check your code for security, performance, and design issues, among others. The documentation for .NET analyzers can be found here.

Main analyzers

Recently the set of analyzer packages produced by this repository have been consolidated. The following table summarizes this information:

NuGet Package Name	Version	Summary
Microsoft.CodeAnalysis.NetAnalyzers		✔️ Primary analyzer package for this repo. Included default for .NET 5+. For earlier targets read more.
Microsoft.CodeAnalysis.BannedApiAnalyzers		✔️ Allows banning use of arbitrary code. Read more.
Microsoft.CodeAnalysis.PublicApiAnalyzers		✔️ Helps library authors monitor changes to their public APIs. Read more.
Microsoft.CodeAnalysis.Analyzers		⚠️ Intended projects providing analyzers and code fixes. Read more.
Roslyn.Diagnostics.Analyzers		⚠️ Rules specific to the Roslyn project, not intended for general consumption. Read more.
Microsoft.CodeAnalysis.FxCopAnalyzers		⛔ Use Microsoft.CodeAnalysis.NetAnalyzers instead. Read more.
Microsoft.CodeQuality.Analyzers		⛔ Use Microsoft.CodeAnalysis.NetAnalyzers instead. Read more.
Microsoft.NetCore.Analyzers		⛔ Use Microsoft.CodeAnalysis.NetAnalyzers instead. Read more.
Microsoft.NetFramework.Analyzers		⛔ Use Microsoft.CodeAnalysis.NetAnalyzers instead. Read more.

Microsoft.CodeAnalysis.NetAnalyzers

Latest stable version:

Latest pre-release version (.NET8 analyzers): here

This is the primary analyzer package for this repo that contains all the .NET code analysis rules (CAxxxx) that are built into the .NET SDK starting .NET5 release. The documentation for CA rules can be found at learn.microsoft.com/visualstudio/code-quality/code-analysis-for-managed-code-warnings.

You do not need to manually install this NuGet package to your project if you are using .NET5 SDK or later. These analyzers are enabled by default for projects targeting .NET5 or later. For projects targeting earlier .NET frameworks, you can enable them in your MSBuild project file by setting one of the following properties:

1. EnableNETAnalyzers

   <PropertyGroup>
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
   </PropertyGroup>
   

2. AnalysisLevel

   <PropertyGroup>
     <AnalysisLevel>latest</AnalysisLevel>
   </PropertyGroup>
   

Microsoft.CodeAnalysis.FxCopAnalyzers

NOTE: Starting version 3.3.2, Microsoft.CodeAnalysis.FxCopAnalyzers has been deprecated in favor of Microsoft.CodeAnalysis.NetAnalyzers. Documentation to migrate from FxCopAnalyzers to NetAnalyzers is available here.

Latest stable version:

This is a migration analyzer package for existing binary FxCop users. It contains all the ported FxCop code analysis rules (CAxxxx). It's recommended to use Microsoft.CodeAnalysis.NetAnalyzers instead. The documentation for that can be found at learn.microsoft.com/visualstudio/code-quality/install-net-analyzers.

The documentation for all the ported and unported FxCop rules can be found at learn.microsoft.com/visualstudio/code-quality/fxcop-rule-port-status.

This analyzer package contains all the ported FxCop rules that are applicable for both .NetCore/.NetStandard and Desktop .NetFramework projects. You do not need to install any separate analyzer package from this repo to get target-framework specific FxCop rules.

The following are subpackages or NuGet dependencies that are automatically installed when you install the Microsoft.CodeAnalysis.FxCopAnalyzers package:

NOTE: Starting version 3.3.2, Microsoft.CodeQuality.Analyzers, Microsoft.NetCore.Analyzers and Microsoft.NetFramework.Analyzers have also been deprecated in favor of Microsoft.CodeAnalysis.NetAnalyzers. Documentation to migrate to NetAnalyzers is available here.

Microsoft.CodeQuality.Analyzers

Latest stable version:

This package contains common code quality improvement rules that are not specific to usage of any particular API. For example, CA1801 (ReviewUnusedParameters) flags parameters that are unused and is part of this package.

Microsoft.NetCore.Analyzers

Latest stable version:

This package contains rules for correct usage of APIs that are present in .NetCore/.NetStandard framework libraries. For example, CA1309 (UseOrdinalStringComparison) flags usages of string compare APIs that don't specify a StringComparison argument. Getting started with NetCore Analyzers

NOTE: This analyzer package is applicable for both .NetCore/.NetStandard and Desktop .NetFramework projects. If the API whose usage is being checked exists only in .NetCore/.NetStandard libraries, then the analyzer will bail out silently for Desktop .NetFramework projects. Otherwise, if the API exists in both .NetCore/.NetStandard and Desktop .NetFramework libraries, the analyzer will run correctly for both .NetCore/.NetStandard and Desktop .NetFramework projects.

Microsoft.NetFramework.Analyzers

Latest stable version:

This package contains rules for correct usage of APIs that are present only in Desktop .NetFramework libraries.

NOTE: The analyzers in this package will silently bail out if installed on a .NetCore/.NetStandard project that do not have the underlying API whose usage is being checked. If future versions of .NetCore/.NetStandard libraries include these APIs, the analyzers will automatically light up on .NetCore/.NetStandard projects that target these libraries.

Other Analyzer Packages

Microsoft.CodeAnalysis.Analyzers

Latest stable version:

Latest pre-release version: here

This package contains rules for correct usage of APIs from the Microsoft.CodeAnalysis NuGet package, i.e. .NET Compiler Platform ("Roslyn") APIs. These are primarily aimed towards helping authors of diagnostic analyzers and code fix providers to invoke the Microsoft.CodeAnalysis APIs in a recommended manner. More info about rules in this package

Roslyn.Diagnostics.Analyzers

Latest stable version:

Latest pre-release version: here

This package contains rules that are very specific to the .NET Compiler Platform ("Roslyn") project, i.e. dotnet/roslyn repo. This analyzer package is not intended for general consumption outside the Roslyn repo. More info about rules in this package

Microsoft.CodeAnalysis.BannedApiAnalyzers

Latest stable version:

Latest pre-release version: here

This package contains customizable rules for identifying references to banned APIs. More info about rules in this package

For instructions on using this analyzer, see Instructions.

Microsoft.CodeAnalysis.PublicApiAnalyzers

Latest stable version:

Latest pre-release version: here

This package contains rules to help library authors monitoring change to their public APIs. More info about rules in this package

For instructions on using this analyzer, see Instructions.

MetaCompilation (prototype)

Created by summer 2015 interns Zoë Petard, Jessica Petty, and Daniel King

The MetaCompilation Analyzer is an analyzer that functions as a tutorial to teach users how to write an analyzer. It uses diagnostics and code fixes to guide the user through the various steps required to create a simple analyzer. It is designed for novice analyzer developers who have some previous programming experience.

For instructions on using this tutorial, see Instructions.

Getting Started

1. Install Visual Studio 2022 or later, with at least the following workloads:
   1. .NET desktop development
   2. .NET Core cross-platform development
   3. Visual Studio extension development
2. Clone this repository
3. Install .NET SDK version specified in .\global.json with "dotnet":
   • Currently, the repository requires the .NET 8 SDK, for which the installer isn't yet published in dotnet.microsoft.com.
   • To install the .NET 8 SDK, see dotnet/installer.
4. Open a command prompt and go to the directory of the Roslyn Analyzer Repo
5. Run the restore and build command: build.cmd(in the command prompt) or .\build.cmd(in PowerShell).
6. Execute tests: test.cmd (in the command prompt) or .\test.cmd (in PowerShell).

Submitting Pull Requests

Prior to submitting a pull request, ensure the build and all tests pass using using steps 4 and 5 above.

Guidelines for contributing a new Code Analysis (CA) rule to the repo

See GuidelinesForNewRules.md for contributing a new Code Analysis rule to the repo.

Versioning Scheme for Analyzer Packages

See VERSIONING.md for the versioning scheme for all analyzer packages built out of this repo.

Recommended version of Analyzer Packages

Recommended Analyzer Package Version:

Required Visual Studio Version: Visual Studio 2019 16.9 RTW or later

Required .NET SDK Version: .NET 5.0 SDK or later

The documentation for .NET SDK Analyzers can be found here