Add Requires analyzer and code fix support

[AArnott]

Why

This repo did not have any Roslyn analyzer or code-fix infrastructure yet, which meant users of Microsoft.VisualStudio.Validation got no IDE help to add the preferred Requires guards or simplify equivalent manual null-check patterns.

What changed

This adds the first analyzer package for the repo and wires it in using a compatibility-aware layout:

• adds separate shared, C#-specific, code-fix/package, and test projects
• splits Roslyn dependency management so shipped analyzer dependencies stay compatible with older VS/SDK baselines while tests use newer Roslyn test packages
• adds four diagnostics and fixes for the current preferred guard forms:
  • VSV0001 suggests Requires.NotNull(value);
  • VSV0002 suggests Requires.Range(value >= 0, nameof(value));
  • VSV0003 replaces supported manual null-check-and-throw patterns with Requires.NotNull(value);
  • VSV0004 removes redundant explicit parameter-name arguments from Requires.NotNull(value, parameterName);
• adds analyzer/code-fix tests covering diagnostic, no-diagnostic, and code-fix scenarios
• adds analyzer package documentation, including a package README and DocFX analyzer pages

Non-obvious details

• analyzer dependencies are intentionally separated into Directory.Packages.Analyzers.props, and Renovate is configured not to update that file automatically
• the repo-level GitVersionBaseDirectory setting was removed so project-local version.json files in the analyzer projects take effect
• the package project is the code-fix project, which packs the shared analyzer, C# analyzer, and code-fix assemblies under analyzers/dotnet/cs/

Validation

• built the solution in Release
• ran the analyzer test project
• resolved remaining compiler and StyleCop warnings introduced by this work

[codecov-commenter]

Codecov Report

❌ Patch coverage is 75.38126% with 113 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.88%. Comparing base (2646d3f) to head (dc1d0a1).
⚠️ Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
...nalyzers.CSharp/CSharpUseRequiresGuardsAnalyzer.cs	66.40%	54 Missing and 30 partials ⚠️
...odeFixes/CSharpUseRequiresGuardsCodeFixProvider.cs	83.97%	15 Missing and 14 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #357      +/-   ##
==========================================
- Coverage   80.50%   77.88%   -2.62%     
==========================================
  Files          11       14       +3     
  Lines         400      859     +459     
  Branches      111      224     +113     
==========================================
+ Hits          322      669     +347     
- Misses         58      126      +68     
- Partials       20       64      +44     

Flag	Coverage Δ
Linux	79.18% <75.38%> (-4.43%)	⬇️
Windows	77.88% <75.38%> (-2.62%)	⬇️

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[Copilot]

Pull request overview

Adds initial Roslyn analyzer + code-fix infrastructure for Microsoft.VisualStudio.Validation to help users adopt the preferred Requires guard patterns, along with packaging, tests, and DocFX documentation.

Changes:

• Introduces analyzer, C# analyzer implementation, and code-fix/packaging projects for Requires guard recommendations (VSV0001–VSV0003).
• Adds analyzer/code-fix test project with Roslyn testing helpers and test coverage for diagnostics + fixes.
• Wires in documentation (DocFX pages + package README) and centralizes analyzer-vs-test Roslyn dependency versions.

Reviewed changes

Copilot reviewed 31 out of 31 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
test/Microsoft.VisualStudio.Validation.Analyzers.Tests/UseRequiresGuardsCodeFixTests.cs	Adds code-fix tests for inserting/replacing Requires guards.
test/Microsoft.VisualStudio.Validation.Analyzers.Tests/UseRequiresGuardsAnalyzerTests.cs	Adds analyzer tests for diagnostics/no-diagnostics scenarios.
test/Microsoft.VisualStudio.Validation.Analyzers.Tests/Microsoft.VisualStudio.Validation.Analyzers.Tests.csproj	New analyzer test project targeting net8.0 (+ net472 on Windows).
test/Microsoft.VisualStudio.Validation.Analyzers.Tests/Helpers/UseRequiresGuardsVerifier.cs	Test verifier wrapper for analyzer/code-fix under test.
test/Microsoft.VisualStudio.Validation.Analyzers.Tests/Helpers/ReferencesHelper.cs	Provides reference assemblies + nuget.config discovery for Roslyn tests.
test/Microsoft.VisualStudio.Validation.Analyzers.Tests/Helpers/CSharpCodeFixVerifier`2.cs	Shared Roslyn test harness utilities.
test/Microsoft.VisualStudio.Validation.Analyzers.Tests/Helpers/CSharpCodeFixVerifier`2+Test.cs	Test fixture configuring references (including Requires assembly).
src/Microsoft.VisualStudio.Validation.Analyzers/version.json	Enables project-local versioning for analyzer assembly.
src/Microsoft.VisualStudio.Validation.Analyzers/Microsoft.VisualStudio.Validation.Analyzers.csproj	New shared analyzer project (non-packable) with Roslyn dependencies.
src/Microsoft.VisualStudio.Validation.Analyzers/KnownTypeNames.cs	Centralizes metadata names used by analyzers.
src/Microsoft.VisualStudio.Validation.Analyzers/DiagnosticIds.cs	Defines diagnostic IDs VSV0001–VSV0003.
src/Microsoft.VisualStudio.Validation.Analyzers/DiagnosticDescriptors.cs	Defines DiagnosticDescriptors for the analyzer package.
src/Microsoft.VisualStudio.Validation.Analyzers.CodeFixes/version.json	Enables project-local versioning for code-fix assembly.
src/Microsoft.VisualStudio.Validation.Analyzers.CodeFixes/README.md	Package README listing analyzer IDs and descriptions.
src/Microsoft.VisualStudio.Validation.Analyzers.CodeFixes/Microsoft.VisualStudio.Validation.Analyzers.CodeFixes.csproj	Packs analyzers + code fixes into Microsoft.VisualStudio.Validation.Analyzers.
src/Microsoft.VisualStudio.Validation.Analyzers.CodeFixes/CSharpUseRequiresGuardsCodeFixProvider.cs	Implements code fixes for VSV0001–VSV0003.
src/Microsoft.VisualStudio.Validation.Analyzers.CSharp/version.json	Enables project-local versioning for C# analyzer assembly.
src/Microsoft.VisualStudio.Validation.Analyzers.CSharp/Microsoft.VisualStudio.Validation.Analyzers.CSharp.csproj	New C#-specific analyzer project.
src/Microsoft.VisualStudio.Validation.Analyzers.CSharp/CSharpUseRequiresGuardsAnalyzer.cs	Implements parameter/if-statement analysis for Requires guard suggestions.
docfx/toc.yml	Adds “Analyzers” section to DocFX navigation.
docfx/analyzers/toc.yml	Adds DocFX TOC for analyzer pages.
docfx/analyzers/index.md	Adds analyzer landing page listing VSV0001–VSV0003.
docfx/analyzers/VSV0001.md	Documents “Add Requires.NotNull” rule.
docfx/analyzers/VSV0002.md	Documents “Add Requires.Range” rule.
docfx/analyzers/VSV0003.md	Documents “Use Requires.NotNull” rule.
Microsoft.VisualStudio.Validation.slnx	Adds new projects/files to the solution.
Directory.Packages.props	Adds Roslyn + test package version properties/entries.
Directory.Packages.Analyzers.props	Introduces analyzer-specific Roslyn dependency pinning (VS-compat).
Directory.Build.targets	Imports analyzer-specific package versions for analyzer projects.
Directory.Build.props	Removes repo-level GitVersionBaseDirectory so analyzer version.json is honored.
.github/renovate.json	Disables Renovate updates for Directory.Packages.Analyzers.props.

[Copilot]

Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated 5 comments.

[drewnoakes]

A nice analyzer and codefix would be to remove the redundant argument name argument:

Requires.NotNull(value, "value");
Requires.NotNull(value, nameof(value));

// ...become...

Requires.NotNull(value);

[AArnott]

Thanks @drewnoakes - I took this on in e1c46ad. I added a VSV0004 analyzer and code fix for the safe redundant cases, so Requires.NotNull(value, "value") and Requires.NotNull(value, nameof(value)) now simplify to Requires.NotNull(value), while cases like escaped identifiers stay untouched where dropping the argument would change the captured caller-expression text.

[Copilot]

Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated 4 comments.

[Copilot]

Pull request overview

Copilot reviewed 32 out of 32 changed files in this pull request and generated 4 comments.