Merge pull request #466 from TimeWarpEngineering/Cramer/2024-08-04/Ac…

…tionSetMethodSourceGen

Add Analyzer to make sure States implement specific CRTP pattern

Directory.Build.props

@@ -1,7 +1,7 @@
 <Project>
   <!-- Set common properties regarding assembly information and nuget packages -->
   <PropertyGroup>
-    <TimeWarpStateVersion>11.0.0-beta.81+8.0.303</TimeWarpStateVersion>
+    <TimeWarpStateVersion>11.0.0-beta.82+8.0.303</TimeWarpStateVersion>
     <Authors>Steven T. Cramer</Authors>
     <Product>TimeWarp State</Product>
     <PackageVersion>$(TimeWarpStateVersion)</PackageVersion>

Source/TimeWarp.State.Analyzer/AnalyzerReleases.Unshipped.md

@@ -5,5 +5,6 @@
 
 Rule ID | Category | Severity | Notes
 --------|----------|----------|-------
+StateInheritanceRule | Design | Error | StateInheritanceAnalyzer
 TW0001 | TimeWarp.State | Error | TimeWarpStateActionAnalyzer
 TWD001 | Debug | Info | TimeWarpStateActionAnalyzer

Source/TimeWarp.State.Analyzer/StateInheritanceAnalyzer.cs

@@ -0,0 +1,52 @@
+namespace TimeWarp.State.Analyzer;
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+using System.Collections.Immutable;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class StateInheritanceAnalyzer : DiagnosticAnalyzer
+{
+    public const string DiagnosticId = "StateInheritanceRule";
+
+    private static readonly LocalizableString Title = "Incorrect State<T> inheritance";
+    private static readonly LocalizableString MessageFormat = "The type argument for State<T> must be the derived class itself";
+    private static readonly LocalizableString Description = "When inheriting from State<T>, T must be the name of the derived class.";
+    private const string Category = "Design";
+
+    private static readonly DiagnosticDescriptor Rule = new(DiagnosticId, Title, MessageFormat, Category, DiagnosticSeverity.Error, isEnabledByDefault: true, description: Description);
+
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get { return ImmutableArray.Create(Rule); } }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
+        context.EnableConcurrentExecution();
+        context.RegisterSyntaxNodeAction(AnalyzeNode, SyntaxKind.ClassDeclaration);
+    }
+
+    private static void AnalyzeNode(SyntaxNodeAnalysisContext context)
+    {
+        var classDeclaration = (ClassDeclarationSyntax)context.Node;
+        BaseTypeSyntax? baseType = classDeclaration.BaseList?.Types.FirstOrDefault();
+
+        if (baseType == null) return;
+
+        var baseTypeSymbol = context.SemanticModel.GetSymbolInfo(baseType.Type).Symbol as INamedTypeSymbol;
+        if (baseTypeSymbol == null || !baseTypeSymbol.Name.Equals("State")) return;
+
+        ITypeSymbol? typeArg = baseTypeSymbol.TypeArguments.FirstOrDefault();
+        if (typeArg == null) return;
+
+        INamedTypeSymbol? derivedTypeSymbol = context.SemanticModel.GetDeclaredSymbol(classDeclaration);
+        if (derivedTypeSymbol == null) return;
+
+        if (!SymbolEqualityComparer.Default.Equals(typeArg, derivedTypeSymbol))
+        {
+            var diagnostic = Diagnostic.Create(Rule, classDeclaration.Identifier.GetLocation());
+            context.ReportDiagnostic(diagnostic);
+        }
+    }
+}