.NET (Microsoft) Fix Analyzer Bug
Overview
Reproduce in an existing test file, minimal code fix, changelog entry. Highest-frequency contributor task.
When to Use
- Analyzer reports when it should not (false positive)
- Analyzer misses case it should report (false negative)
- Code fix produces wrong transformation
- Issue title includes
RCS####,RR####,CS####, orRCF####
Not for: new rules (add-analyzer, add-refactoring, add-compiler-diagnostic-fix), deprecation (deprecate-analyzer-or-refactoring).
For test patterns use in-repo verifiers — not public NuGet testing docs.
Quick Reference
| Prefix | Code | Tests | Verifier |
|---|---|---|---|
| RCS1 | Analyzers/CSharp/Analysis/ |
Tests/Analyzers.Tests/ |
AbstractCSharpDiagnosticVerifier |
| RCS0 | Formatting.Analyzers/CSharp/ |
Tests/Formatting.Analyzers.Tests/ |
AbstractCSharpDiagnosticVerifier |
| RCS9 | CodeAnalysis.Analyzers/CSharp/ |
Tests/CodeAnalysis.Analyzers.Tests/ |
AbstractCSharpDiagnosticVerifier |
| RR | Refactorings/CSharp/Refactorings/ |
Tests/Refactorings.Tests/ |
AbstractCSharpRefactoringVerifier |
| CS / RCF | CodeFixes/CSharp/CodeFixes/ |
Tests/CodeFixes.Tests/ |
AbstractCSharpCompilerDiagnosticFixVerifier |
Search DiagnosticIdentifiers.X / DiagnosticRules.X / CompilerDiagnosticIdentifiers.* in generated files. Roslynator analyzer code fixes live in matching .CodeFixes projects.
Implementation
Add [Fact] to existing *Tests.cs — new file only if none exists.
| Case | Method |
|---|---|
| False positive | VerifyNoDiagnosticAsync |
| False negative | VerifyDiagnosticAsync with `[ |
| Analyzer/refactoring fix regression | VerifyDiagnosticAndFixAsync |
| Compiler fix regression | VerifyFixAsync (no `[ |
Config-dependent: options: Options.AddConfigOption(...).
Verify (adjust project and filter):
cd src && dotnet build Roslynator.sln
cd src && dotnet test Tests/Analyzers.Tests --no-build --filter "FullyQualifiedName~RCS####"
cd src && dotnet test Tests/CodeFixes.Tests --no-build --filter "FullyQualifiedName~CS####"
cd src && dotnet format Roslynator.sln --no-restore --verify-no-changes --severity info
Changelog examples: references/changelog-examples.md.
Pull request
When the fix targets a GitHub issue, the PR body must include a closing keyword on its own line (same pattern as recent analyzer fix PRs):
Fixes #NNNN
Use Fixes #NNNN or Closes #NNNN. A markdown link such as [#1812](https://github.com/dotnet/roslynator/issues/1812) does not create a GitHub issue reference and will not auto-close the issue.
In CHANGELOG.md, end the entry with ([PR](https://github.com/dotnet/roslynator/pull/NNNN)) (see references/changelog-examples.md). Do not use an issue link there.
Place Fixes #NNNN after the Summary bullets and before the Test plan, for example:
## Summary
- …
Fixes #1812
## Test plan
- …
Common Mistakes
| Mistake | Fix |
|---|---|
Copy test pattern from analyzers-testing.md |
In-repo AbstractCSharpDiagnosticVerifier + DiagnosticRules.X |
Copy from compiler-diagnostic-fixes-testing.md |
In-repo AbstractCSharpCompilerDiagnosticFixVerifier + CompilerDiagnosticIdentifiers.* |
| New test file per case | Extend existing RCS####...Tests.cs or CS####...Tests.cs |
Change Analyzers.xml for logic bugs |
Metadata only for docs/severity defaults |
| `[ | ... |
| Full test suite | Filter by rule id is enough |
| Skip test | CONTRIBUTING.md requires tests for bug fixes |
Changelog ends with issue link ([#NNNN](.../issues/...)) |
End with ([PR](https://github.com/dotnet/roslynator/pull/NNNN)) |
| Markdown-only issue link in PR body | Use Fixes #NNNN so GitHub links and auto-closes the issue |