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Add analyzer for Enum.GetNames() with generated alternative (#209)
* Initial plan * Add GetNamesAnalyzer, GetNamesCodeFixProvider, and comprehensive tests Co-authored-by: andrewlock <18755388+andrewlock@users.noreply.github.com> * Tweaks to GetNames * Add analyzer tests --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: andrewlock <18755388+andrewlock@users.noreply.github.com> Co-authored-by: Andrew Lock <andrewlock.net@gmail.com>
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Lines changed: 669 additions & 1 deletion

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‎src/NetEscapades.EnumGenerators/Diagnostics/UsageAnalyzers/GetNamesAnalyzer.cs‎

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using System.Collections.Immutable;
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using Microsoft.CodeAnalysis;
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using Microsoft.CodeAnalysis.CSharp;
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using Microsoft.CodeAnalysis.CSharp.Syntax;
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using Microsoft.CodeAnalysis.Diagnostics;
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namespace NetEscapades.EnumGenerators.Diagnostics.UsageAnalyzers;
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[DiagnosticAnalyzer(LanguageNames.CSharp)]
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public class GetNamesAnalyzer : DiagnosticAnalyzer
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{
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public const string DiagnosticId = "NEEG008";
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public static readonly DiagnosticDescriptor Rule = new(
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#pragma warning disable RS2008 // Enable Analyzer Release Tracking
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id: DiagnosticId,
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#pragma warning restore RS2008
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title: "Use generated GetNames() instead of Enum.GetNames()",
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messageFormat: "Use generated GetNames() instead of Enum.GetNames() for better performance on enum '{0}'",
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category: "Usage",
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defaultSeverity: DiagnosticSeverity.Info,
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isEnabledByDefault: true);
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public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics
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=> ImmutableArray.Create(Rule);
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public override void Initialize(AnalysisContext context)
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{
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context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
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context.EnableConcurrentExecution();
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context.RegisterCompilationStartAction(ctx =>
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{
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var (enumExtensionsAttr, externalEnumTypes) = AnalyzerHelpers.GetEnumExtensionAttributes(ctx.Compilation);
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if (enumExtensionsAttr is null || externalEnumTypes is null)
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{
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return;
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}
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ctx.RegisterSyntaxNodeAction(
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c => AnalyzeInvocation(c, enumExtensionsAttr, externalEnumTypes),
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SyntaxKind.InvocationExpression);
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});
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}
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private static void AnalyzeInvocation(SyntaxNodeAnalysisContext context, INamedTypeSymbol enumExtensionsAttr, ExternalEnumDictionary externalEnumTypes)
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{
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var invocation = (InvocationExpressionSyntax)context.Node;
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if (invocation.ArgumentList.Arguments.Count is not (0 or 1)
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|| invocation.Expression is not MemberAccessExpressionSyntax memberAccess
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|| memberAccess.Name.Identifier.Text != nameof(Enum.GetNames))
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{
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// can't be the one we want
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return;
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}
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// Get the symbol information for the invocation
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var symbolInfo = context.SemanticModel.GetSymbolInfo(invocation);
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if (symbolInfo.Symbol is not IMethodSymbol methodSymbol)
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{
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return;
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}
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// Verify this is the GetNames() method from System.Enum
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if (methodSymbol.Name != nameof(Enum.GetNames) ||
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methodSymbol.ContainingType.SpecialType != SpecialType.System_Enum)
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{
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return;
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}
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ITypeSymbol? enumType = null;
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// Handle two basic patterns:
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// 1. Enum.GetNames(typeof(TEnum)) - has 1 parameter
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// 2. Enum.GetNames<TEnum>() - has 0 parameters, is generic
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if (methodSymbol is { IsGenericMethod: true, TypeArguments.Length: 1 })
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{
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// Pattern: Enum.GetNames<TEnum>()
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if (invocation.ArgumentList.Arguments.Count is not 0)
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{
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return;
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}
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enumType = methodSymbol.TypeArguments[0];
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}
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else if (methodSymbol.Parameters.Length is 1
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&& invocation.ArgumentList.Arguments is [{ Expression: TypeOfExpressionSyntax typeOfExpression }])
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{
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// Pattern: Enum.GetNames(typeof(TEnum))
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enumType = context.SemanticModel.GetTypeInfo(typeOfExpression.Type).Type;
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}
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if (enumType is null || enumType.TypeKind != TypeKind.Enum)
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{
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return;
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}
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if (!AnalyzerHelpers.IsEnumWithExtensions(enumType, enumExtensionsAttr, externalEnumTypes, out var extensionType))
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{
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return;
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}
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// Report the diagnostic
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var diagnostic = Diagnostic.Create(
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descriptor: Rule,
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location: invocation.GetLocation(),
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messageArgs: enumType.Name,
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properties: ImmutableDictionary.CreateRange<string, string?>([
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new(AnalyzerHelpers.ExtensionTypeNameProperty, extensionType),
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]));
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context.ReportDiagnostic(diagnostic);
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}
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}

‎src/NetEscapades.EnumGenerators/Diagnostics/UsageAnalyzers/GetNamesCodeFixProvider.cs‎

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using System.Collections.Immutable;
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using System.Composition;
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using Microsoft.CodeAnalysis;
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using Microsoft.CodeAnalysis.CodeActions;
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using Microsoft.CodeAnalysis.CodeFixes;
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using Microsoft.CodeAnalysis.CSharp.Syntax;
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using Microsoft.CodeAnalysis.Editing;
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using Microsoft.CodeAnalysis.Simplification;
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namespace NetEscapades.EnumGenerators.Diagnostics.UsageAnalyzers;
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[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(GetNamesCodeFixProvider)), Shared]
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public class GetNamesCodeFixProvider : CodeFixProviderBase
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{
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private const string Title = "Replace with generated GetNames()";
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public sealed override ImmutableArray<string> FixableDiagnosticIds
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=> ImmutableArray.Create(GetNamesAnalyzer.DiagnosticId);
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public sealed override Task RegisterCodeFixesAsync(CodeFixContext context)
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{
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if (!context.Diagnostics.IsDefaultOrEmpty)
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{
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// Register a code action for GetNames() replacement
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context.RegisterCodeFix(
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CodeAction.Create(
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title: Title,
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createChangedDocument: c => FixAllAsync(context.Document, context.Diagnostics, c),
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equivalenceKey: Title),
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context.Diagnostics);
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}
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return Task.CompletedTask;
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}
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protected override Task FixWithEditor(DocumentEditor editor, Diagnostic diagnostic,
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INamedTypeSymbol extensionTypeSymbol,
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CancellationToken cancellationToken)
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{
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// Find the invocation node at the diagnostic location
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var node = editor.OriginalRoot.FindNode(diagnostic.Location.SourceSpan);
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if (node is not InvocationExpressionSyntax invocation)
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{
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return Task.CompletedTask;
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}
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// Create new invocation: ExtensionsClass.GetNames()
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var generator = editor.Generator;
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var newInvocation = generator.InvocationExpression(
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generator.MemberAccessExpression(generator.TypeExpression(extensionTypeSymbol), "GetNames"))
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.WithTriviaFrom(invocation)
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.WithAdditionalAnnotations(Simplifier.AddImportsAnnotation, Simplifier.Annotation);
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editor.ReplaceNode(invocation, newInvocation);
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return Task.CompletedTask;
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}
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}

‎tests/NetEscapades.EnumGenerators.IntegrationTests/.editorconfig‎

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@@ -7,4 +7,5 @@ dotnet_diagnostic.NEEG003.severity = error
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dotnet_diagnostic.NEEG004.severity = error
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dotnet_diagnostic.NEEG005.severity = error
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dotnet_diagnostic.NEEG006.severity = error
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dotnet_diagnostic.NEEG007.severity = error
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dotnet_diagnostic.NEEG007.severity = error
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dotnet_diagnostic.NEEG008.severity = error

‎tests/NetEscapades.EnumGenerators.IntegrationTests/AnalyzerTests.cs‎

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#endif
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#pragma warning restore NEEG007
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}
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[Fact]
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public void Neeg008Testing()
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{
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#pragma warning disable NEEG008
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_ = Enum.GetNames(typeof(FlagsEnum));
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#if NET5_0_OR_GREATER
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_ = Enum.GetNames<FlagsEnum>().Length;
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#endif
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#pragma warning restore NEEG008
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}
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}

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