Add Roslyn Analyzer project

src/Carter/Analyzers/CarterModuleShouldNotHaveDependenciesAnalyzer.cs

@@ -0,0 +1,71 @@
+namespace Carter.Analyzers;
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+internal sealed class CarterModuleShouldNotHaveDependenciesAnalyzer : DiagnosticAnalyzer
+{
+    public override void Initialize(AnalysisContext context)
+    {
+        context.EnableConcurrentExecution();
+        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
+        context.RegisterCompilationStartAction(OnCompilationStart);
+    }
+
+    private static void OnCompilationStart(CompilationStartAnalysisContext context)
+    {
+        var carterModuleType = context.Compilation.GetTypeByMetadataName("Carter.ICarterModule");
+        if (carterModuleType is null)
+        {
+            return;
+        }
+
+        context.RegisterSymbolAction(ctx => OnTypeAnalysis(ctx, carterModuleType), SymbolKind.NamedType);
+    }
+
+    private static void OnTypeAnalysis(SymbolAnalysisContext context, INamedTypeSymbol carterModuleType)
+    {
+        var typeSymbol = (INamedTypeSymbol)context.Symbol;
+        if (!typeSymbol.Interfaces.Contains(carterModuleType, SymbolEqualityComparer.Default))
+        {
+            return;
+        }
+
+        foreach (var constructor in typeSymbol.Constructors)
+        {
+            if (constructor.DeclaredAccessibility == Accessibility.Private || constructor.Parameters.Length == 0)
+            {
+                continue;
+            }
+
+            foreach (var syntaxReference in constructor.DeclaringSyntaxReferences)
+            {
+                var node = syntaxReference.GetSyntax();
+                SyntaxToken identifier;
+                if (node is ConstructorDeclarationSyntax constructorDeclaration)
+                {
+                    identifier = constructorDeclaration.Identifier;
+                } else if (node is RecordDeclarationSyntax recordDeclaration)
+                {
+                    identifier = recordDeclaration.Identifier;
+                }
+                else
+                {
+                    continue;
+                }
+
+                var diagnostic = Diagnostic.Create(
+                    DiagnosticDescriptors.CarterModuleShouldNotHaveDependencies,
+                    identifier.GetLocation(),
+                    identifier.Text
+                );
+                context.ReportDiagnostic(diagnostic);
+            }
+        }
+    }
+
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = [DiagnosticDescriptors.CarterModuleShouldNotHaveDependencies];
+}

src/Carter/Analyzers/DiagnosticDescriptors.cs

@@ -0,0 +1,16 @@
+using Microsoft.CodeAnalysis;
+
+namespace Carter.Analyzers;
+
+internal static class DiagnosticDescriptors
+{
+   public static readonly DiagnosticDescriptor CarterModuleShouldNotHaveDependencies = new(
+      "CARTER1",
+      "Carter module should not have dependencies",
+      "'{0}' should not have dependencies",
+      "Usage",
+      DiagnosticSeverity.Warning,
+      true,
+      "When a class implements ICarterModule, it should not have any dependencies. This is because Carter uses minimal APIs and dependencies should be declared in the request delegate."
+   );
+}

src/Carter/Carter.csproj

@@ -13,21 +13,27 @@
         <AllowedOutputExtensionsInPackageBuildOutputFolder>$(AllowedOutputExtensionsInPackageBuildOutputFolder);.pdb</AllowedOutputExtensionsInPackageBuildOutputFolder>
         <MinVerSkip Condition="'$(Configuration)' == 'Debug'">true</MinVerSkip>
         <PackageReadmeFile>README.md</PackageReadmeFile>
+        <EnforceExtendedAnalyzerRules>true</EnforceExtendedAnalyzerRules>
+        <NoWarn>RS2008</NoWarn>
     </PropertyGroup>
     <ItemGroup>
         <None Include="..\..\media\carterlogo.png" Pack="true" PackagePath="\" />
         <None Include="..\..\README.md" Pack="true" PackagePath="\"/>
+        <None Include="$(OutputPath)\$(AssemblyName).dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
     </ItemGroup>
     <ItemGroup>
         <FrameworkReference Include="Microsoft.AspNetCore.App" />
     </ItemGroup>
     <ItemGroup>
         <PackageReference Include="FluentValidation" Version="11.8.0" />
+        <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.7.0" PrivateAssets="compile" />
         <PackageReference Include="Microsoft.Extensions.DependencyModel" Version="8.0.0" />
         <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="all" />
         <PackageReference Include="MinVer" Version="2.5.0">
             <PrivateAssets>all</PrivateAssets>
         </PackageReference>
-
+    </ItemGroup>
+    <ItemGroup>
+        <InternalsVisibleTo Include="$(AssemblyName).Tests" />
     </ItemGroup>
 </Project>

src/Carter/DependencyContextAssemblyCatalog.cs

@@ -89,7 +89,9 @@ private static Assembly SafeLoadAssembly(AssemblyName assemblyName)
     {
         try
         {
+#pragma warning disable RS1035
             return Assembly.Load(assemblyName);
+#pragma warning restore RS1035
         }
         catch (Exception)
         {

src/Carter/ModelBinding/BindExtensions.cs

@@ -88,12 +88,14 @@ public static async Task BindAndSaveFile(this HttpRequest request, string saveLo
 
     private static async Task SaveFileInternal(IFormFile file, string saveLocation, string fileName = "")
     {
+#pragma warning disable RS1035
         if (!Directory.Exists(saveLocation))
             Directory.CreateDirectory(saveLocation);
 
         fileName = !string.IsNullOrWhiteSpace(fileName) ? fileName : file.FileName;
 
         using (var fileToSave = File.Create(Path.Combine(saveLocation, fileName)))
             await file.CopyToAsync(fileToSave);
+#pragma warning restore RS1035
     }
 }