Warn users if not using CancellationToken

.gitattributes

@@ -1 +1 @@
-* text=auto eol=lf
+* text=auto

src/Immediate.Handlers.Analyzers/AnalyzerReleases.Shipped.md

@@ -4,12 +4,21 @@
 
 Rule ID | Category | Severity | Notes
 --------|----------|----------|--------------------
-IHR0001 | ImmediateHandler | Error    | HandlerClassAnalyzer
-IHR0002 | ImmediateHandler | Error    | HandlerClassAnalyzer
-IHR0005 | ImmediateHandler | Error    | HandlerClassAnalyzer
-IHR0006 | ImmediateHandler | Error    | BehaviorsAnalyzer
-IHR0007 | ImmediateHandler | Error    | BehaviorsAnalyzer
-IHR0008 | ImmediateHandler | Error    | BehaviorsAnalyzer
+IHR0001 | ImmediateHandler | Error | HandlerClassAnalyzer
+IHR0002 | ImmediateHandler | Error | HandlerClassAnalyzer
+IHR0005 | ImmediateHandler | Error | HandlerClassAnalyzer
+IHR0006 | ImmediateHandler | Error | BehaviorsAnalyzer
+IHR0007 | ImmediateHandler | Error | BehaviorsAnalyzer
+IHR0008 | ImmediateHandler | Error | BehaviorsAnalyzer
 IHR0009 | ImmediateHandler | Error | HandlerClassAnalyzer
 IHR0010 | ImmediateHandler | Error | HandlerClassAnalyzer
 IHR0011 | ImmediateHandler | Error | HandlerClassAnalyzer
+
+
+## Release 1.5
+
+### New Rules
+
+Rule ID | Category | Severity | Notes
+--------|----------|----------|--------------------
+IHR0012 | ImmediateHandler | Warning | HandlerClassAnalyzer

src/Immediate.Handlers.Analyzers/DiagnosticIds.cs

@@ -14,4 +14,5 @@ internal static class DiagnosticIds
 	public const string IHR0009HandlerMethodMustBeStatic = "IHR0009";
 	public const string IHR0010HandlerMethodMustBeUnique = "IHR0010";
 	public const string IHR0011HandlerMethodMustBePrivate = "IHR0011";
+	public const string IHR0012HandlerShouldUseCancellationToken = "IHR0012";
 }

src/Immediate.Handlers.Analyzers/HandlerClassAnalyzer.cs

@@ -73,6 +73,17 @@ public sealed class HandlerClassAnalyzer : DiagnosticAnalyzer
 			description: "Static handler method must be static."
 		);
 
+	public static readonly DiagnosticDescriptor HandlerShouldUseCancellationToken =
+		new(
+			id: DiagnosticIds.IHR0012HandlerShouldUseCancellationToken,
+			title: "Handler method should use CancellationToken",
+			messageFormat: "Method '{0}' should receive a `CancellationToken`",
+			category: "ImmediateHandler",
+			defaultSeverity: DiagnosticSeverity.Warning,
+			isEnabledByDefault: true,
+			description: "Handlers should use CancellationToken to properly support cancellation."
+		);
+
 	public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } =
 		ImmutableArray.Create(
 		[
@@ -82,6 +93,7 @@ public sealed class HandlerClassAnalyzer : DiagnosticAnalyzer
 			HandlerMethodMustBeStatic,
 			HandlerMethodMustBeUnique,
 			HandlerMethodMustBePrivate,
+			HandlerShouldUseCancellationToken,
 		]);
 
 	public override void Initialize(AnalysisContext context)
@@ -192,6 +204,17 @@ private static void AnalyzeSymbol(SymbolAnalysisContext context)
 					);
 				}
 
+				if (!methodSymbol.Parameters[^1].Type.IsCancellationToken())
+				{
+					context.ReportDiagnostic(
+						Diagnostic.Create(
+							HandlerShouldUseCancellationToken,
+							methodSymbol.Locations[0],
+							methodSymbol.Name
+						)
+					);
+				}
+
 				break;
 			}
 

src/Immediate.Handlers.Analyzers/ITypeSymbolExtensions.cs

@@ -45,4 +45,19 @@ typeSymbol is
 	public static bool ImplementsBehavior(this INamedTypeSymbol typeSymbol) =>
 		typeSymbol.IsBehavior2()
 		|| (typeSymbol.BaseType is not null && ImplementsBehavior(typeSymbol.BaseType.OriginalDefinition));
+
+	public static bool IsCancellationToken(this ITypeSymbol typeSymbol) =>
+		typeSymbol is INamedTypeSymbol
+		{
+			Name: "CancellationToken",
+			ContainingNamespace:
+			{
+				Name: "Threading",
+				ContainingNamespace:
+				{
+					Name: "System",
+					ContainingNamespace.IsGlobalNamespace: true
+				}
+			}
+		};
 }

tests/Immediate.Handlers.Tests/AnalyzerTests/HandlerClassAnalyzerTests/Tests.HandleMethodShouldUseCancellationToken.cs

@@ -0,0 +1,36 @@
+using Immediate.Handlers.Analyzers;
+using Immediate.Handlers.Tests.Helpers;
+
+namespace Immediate.Handlers.Tests.AnalyzerTests.HandlerClassAnalyzerTests;
+
+[System.Diagnostics.CodeAnalysis.SuppressMessage("Naming", "CA1724:Type names should not match namespaces", Justification = "Not being consumed by other code")]
+public partial class Tests
+{
+	[Fact]
+	public async Task HandleMethodWithoutCancellationToken_AlertDiagnostic() =>
+		await AnalyzerTestHelpers.CreateAnalyzerTest<HandlerClassAnalyzer>(
+			"""
+			using System;
+			using System.Collections.Generic;
+			using System.IO;
+			using System.Linq;
+			using System.Net.Http;
+			using System.Threading;
+			using System.Threading.Tasks;
+			using Immediate.Handlers.Shared;
+
+			[Handler]
+			public class GetUsersQuery
+			{
+				public record Query;
+
+				private static ValueTask<int> {|IHR0012:HandleAsync|}(
+					Query _)
+				{
+					return ValueTask.FromResult(0);
+				}
+			}
+			""",
+			DriverReferenceAssemblies.Normal
+		).RunAsync();
+}