feat: add analyzer for direct command handler calls

Stl.Fusion.sln

@@ -114,6 +114,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MiniRpc", "samples\MiniRpc\
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MultiServerRpc", "samples\MultiServerRpc\MultiServerRpc.csproj", "{DDD38FE8-3105-44E6-9128-921B0713FF64}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Stl.Analyzers", "src\Stl.Analyzers\Stl.Analyzers.csproj", "{A36C2D5F-65EA-4170-ABE4-7CD9A15B381E}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -250,6 +252,10 @@ Global
 		{DDD38FE8-3105-44E6-9128-921B0713FF64}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{DDD38FE8-3105-44E6-9128-921B0713FF64}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{DDD38FE8-3105-44E6-9128-921B0713FF64}.Release|Any CPU.Build.0 = Release|Any CPU
+		{A36C2D5F-65EA-4170-ABE4-7CD9A15B381E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{A36C2D5F-65EA-4170-ABE4-7CD9A15B381E}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{A36C2D5F-65EA-4170-ABE4-7CD9A15B381E}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{A36C2D5F-65EA-4170-ABE4-7CD9A15B381E}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -289,6 +295,7 @@ Global
 		{5A8530A3-E69B-4BD3-B7A7-01A916D166EB} = {A50B98CF-9AA1-4622-B2AD-5E17610115A7}
 		{99131CAD-DDC3-4B1A-ABB8-63E0FF32B03E} = {61E78666-E338-4F6B-8CD8-8CD5E13B7C54}
 		{DDD38FE8-3105-44E6-9128-921B0713FF64} = {61E78666-E338-4F6B-8CD8-8CD5E13B7C54}
+		{A36C2D5F-65EA-4170-ABE4-7CD9A15B381E} = {A50B98CF-9AA1-4622-B2AD-5E17610115A7}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {B50610D6-2B28-4258-98A2-A0B486FD5907}

src/Directory.Build.props

@@ -50,7 +50,7 @@
   </ItemGroup>
 
   <!-- Global usings -->
-  <ItemGroup Condition="!($(MSBuildProjectFile.Contains('Generators')))">
+  <ItemGroup Condition="!($(MSBuildProjectFile.Contains('Generators'))) and !($(MSBuildProjectFile.Contains('Analyzers')))">
     <Using Include="System.Console" Static="True" />
     <Using Include="System.Collections" />
     <Using Include="System.Collections.Immutable" />

src/Stl.Analyzers/CommandHandlerAnalyzer.cs

@@ -0,0 +1,71 @@
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace Stl.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class CommandHandlerAnalyzer : DiagnosticAnalyzer
+{
+    private static readonly DiagnosticDescriptor DirectCallDiagnostic =
+        new(
+            "STLC0001",
+            "Invalid command handler call",
+            "Direct command handler calls on command service proxies are not allowed",
+            "Test",
+            DiagnosticSeverity.Warning,
+            isEnabledByDefault: true
+        );
+
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } =
+        ImmutableArray.Create(DirectCallDiagnostic);
+
+    public override void Initialize(AnalysisContext context)
+    {
+        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.Analyze | GeneratedCodeAnalysisFlags.ReportDiagnostics);
+        context.EnableConcurrentExecution();
+
+        context.RegisterSyntaxNodeAction(CheckCommandHandler, SyntaxKind.InvocationExpression);
+    }
+
+    private void CheckCommandHandler(SyntaxNodeAnalysisContext context)
+    {
+        if (context.Node is not InvocationExpressionSyntax invocation)
+            return;
+
+        if (context.SemanticModel.GetSymbolInfo(invocation, cancellationToken: context.CancellationToken).Symbol is not IMethodSymbol methodSymbol)
+            return;
+
+        var syntaxReference = methodSymbol.DeclaringSyntaxReferences.FirstOrDefault();
+
+        if (syntaxReference is null)
+            return;
+
+        SyntaxNode declaration = syntaxReference.GetSyntax(context.CancellationToken);
+
+        if (declaration is not MethodDeclarationSyntax method)
+            return;
+
+        // check if the called method has the CommandHandler attribute
+        // this is a very naive implementation, the namespace should be checked as well
+        bool isCommandHandler = method.AttributeLists
+            .SelectMany(x => x.Attributes)
+            .Any(
+                attribute =>
+                    string.Equals(
+                        attribute.Name.ToString(),
+                        "CommandHandler",
+                        StringComparison.Ordinal
+                    )
+            );
+
+        if (!isCommandHandler)
+            return;
+
+        var diagnostic = Diagnostic.Create(DirectCallDiagnostic, context.Node.GetLocation());
+
+        context.ReportDiagnostic(diagnostic);
+    }
+}

src/Stl.Analyzers/Stl.Analyzers.csproj

@@ -0,0 +1,16 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFrameworks>netstandard2.0;net7.0</TargetFrameworks>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+        <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
+        <Description>Stl.Analyzers - Roslyn analyzers for common issues.</Description>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" />
+        <PackageReference Include="Microsoft.CodeAnalysis.CSharp" />
+    </ItemGroup>
+
+</Project>