Merge saga diagnostics now that they're both error

src/NServiceBus.Core.Analyzer.Tests.Common/Sagas/SagaAnalyzerTests.cs

@@ -35,7 +35,7 @@ public class Msg1 : ICommand
     public string CorrId { get; set; }
 }";
 
-        return Assert([DiagnosticIds.SagaMappingExpressionCanBeRewritten], source, mustCompile: false);
+        return Assert([DiagnosticIds.SagaMappingExpressionCanBeSimplified], source, mustCompile: false);
     }
 
     [Test]
@@ -143,6 +143,40 @@ public class Msg1 : ICommand;
         return Assert(source);
     }
 
+    [Test]
+    public Task NoDiagnosticForConfigureNotFoundHandler()
+    {
+        var source =
+            @"using System;
+using System.Threading.Tasks;
+using NServiceBus;
+public class MySaga : Saga<MyData>, IAmStartedByMessages<Msg1>
+{
+    protected override void ConfigureHowToFindSaga(SagaPropertyMapper<MyData> mapper)
+    {
+        mapper.MapSaga(saga => saga.CorrId).ToMessage<Msg1>(msg => msg.CorrId);
+
+        mapper.ConfigureNotFoundHandler<MyNotFoundHandler>();
+    }
+    public Task Handle(Msg1 message, IMessageHandlerContext context) => throw new NotImplementedException();
+}
+public class MyData : ContainSagaData
+{
+    public string CorrId { get; set; }
+    public string OtherId { get; set; }
+}
+public class Msg1 : ICommand
+{
+    public string CorrId { get; set; }
+}
+public class MyNotFoundHandler : ISagaNotFoundHandler
+{
+	public Task Handle(object message, IMessageProcessingContext context) => Task.CompletedTask;
+}";
+
+        return Assert([], source, mustCompile: false);
+    }
+
     [Test]
     public Task SagaDataPropertyHasNonPublicSetter()
     {

src/NServiceBus.Core.Analyzer/DiagnosticIds.cs

@@ -23,7 +23,7 @@ public static class DiagnosticIds
         public const string SagaShouldNotImplementNotFoundHandler = "NSB0015";
         public const string CorrelationPropertyTypeMustMatchMessageMappingExpressions = "NSB0016";
         public const string ToSagaMappingMustBeToAProperty = "NSB0017";
-        public const string SagaMappingExpressionCanBeRewritten = "NSB0018";
+        public const string SagaMappingExpressionCanBeRewritten = "NSB0018"; // Unused, merged into NSB0004
         public const string DoNotEnableFeaturesInDefaults = "NSB0019";
         public const string HandlerInjectsMessageSession = "NSB0020";
         public const string AddHandlerOnSagaType = "NSB0021";

src/NServiceBus.Core.Analyzer/Sagas/SagaAnalyzer.cs

@@ -29,8 +29,7 @@ public class SagaAnalyzer : DiagnosticAnalyzer
             SagaDiagnostics.SagaShouldNotHaveIntermediateBaseClass,
             SagaDiagnostics.SagaShouldNotImplementNotFoundHandler,
             SagaDiagnostics.ToSagaMappingMustBeToAProperty,
-            SagaDiagnostics.CorrelationPropertyTypeMustMatchMessageMappingExpressions,
-            SagaDiagnostics.SagaMappingExpressionCanBeRewritten
+            SagaDiagnostics.CorrelationPropertyTypeMustMatchMessageMappingExpressions
         ];
 
         public override void Initialize(AnalysisContext context)
@@ -153,25 +152,14 @@ static void AnalyzeSagaClass(SyntaxNodeAnalysisContext context, ClassDeclaration
                         }
                     }
                 }
-                else if (nonCustomFinderMapping.Select(m => m.ToSagaSyntax).Distinct().Count() > 1)
-                {
-                    Diagnostic diagnostic = CreateMappingRewritingDiagnostic(
-                        fixerTitle: "Simplify saga mapping expression",
-                        descriptor: SagaDiagnostics.SagaMappingExpressionCanBeSimplified,
-                        location: saga.ConfigureHowToFindMethod.Identifier.GetLocation(),
-                        newMappingForLocation: null,
-                        correlationId: assumedCorrelationId,
-                        saga: saga);
-                    context.ReportDiagnostic(diagnostic);
-                }
                 else
                 {
                     var mappingMethodNames = nonCustomFinderMapping.Select(m => (m.MessageTypeSyntax?.Parent?.Parent as GenericNameSyntax)?.Identifier.ValueText);
                     if (mappingMethodNames.Any(name => name is "ConfigureMapping" or "ConfigureHeaderMapping"))
                     {
                         Diagnostic diagnostic = CreateMappingRewritingDiagnostic(
                             fixerTitle: "Rewrite saga mapping expression",
-                            descriptor: SagaDiagnostics.SagaMappingExpressionCanBeRewritten,
+                            descriptor: SagaDiagnostics.SagaMappingExpressionCanBeSimplified,
                             location: saga.ConfigureHowToFindMethod.Identifier.GetLocation(),
                             newMappingForLocation: null,
                             correlationId: assumedCorrelationId,

src/NServiceBus.Core.Analyzer/Sagas/SagaDiagnostics.cs

@@ -17,7 +17,7 @@ static class SagaDiagnostics
         public static readonly DiagnosticDescriptor SagaMappingExpressionCanBeSimplified = new(
             id: DiagnosticIds.SagaMappingExpressionCanBeSimplified,
             title: "Saga mapping expressions must be rewritten",
-            messageFormat: "The saga mapping contains multiple .ToSaga(…) expressions which must be rewritten using mapper.MapSaga(…).ToMessage<T>(…) syntax. Use the code fix to transition to the new syntax.",
+            messageFormat: "This saga mapping expression must be rewritten using mapper.MapSaga(…).ToMessage<T>(…) syntax. Use the code fix to transition to the new syntax.",
             category: DiagnosticCategory,
             defaultSeverity: DiagnosticSeverity.Error,
             isEnabledByDefault: true);
@@ -129,13 +129,5 @@ static class SagaDiagnostics
             category: DiagnosticCategory,
             defaultSeverity: DiagnosticSeverity.Error,
             isEnabledByDefault: true);
-
-        public static readonly DiagnosticDescriptor SagaMappingExpressionCanBeRewritten = new(
-            id: DiagnosticIds.SagaMappingExpressionCanBeRewritten,
-            title: "Saga mapping expressions must be rewritten",
-            messageFormat: "This saga mapping expression must be rewritten using mapper.MapSaga(…).ToMessage<T>(…) syntax. Use the code fix to transition to the new syntax.",
-            category: DiagnosticCategory,
-            defaultSeverity: DiagnosticSeverity.Error,
-            isEnabledByDefault: true);
     }
 }