WIP

Author: BrennanConroy

src/Framework/AspNetCoreAnalyzers/src/Analyzers/DiagnosticDescriptors.cs

@@ -248,4 +248,13 @@ internal static class DiagnosticDescriptors
         DiagnosticSeverity.Info,
         isEnabledByDefault: true,
         helpLinkUri: AnalyzersLink);
+
+    internal static readonly DiagnosticDescriptor UseCreateHostBuilderInsteadOfCreateWebHostBuilder = new(
+        "ASP0029",
+        CreateLocalizableResourceString(nameof(Resources.Analyzer_UseCreateHostBuilderInsteadOfCreateWebHostBuilder_Title)),
+        CreateLocalizableResourceString(nameof(Resources.Analyzer_UseCreateHostBuilderInsteadOfCreateWebHostBuilder_Message)),
+        Usage,
+        DiagnosticSeverity.Warning,
+        isEnabledByDefault: true,
+        helpLinkUri: AnalyzersLink);
 }

src/Framework/AspNetCoreAnalyzers/src/Analyzers/Resources.resx

@@ -333,4 +333,10 @@
   <data name="Analyzer_KestrelShouldListenOnIPv6AnyInsteadOfIpAny_Message" xml:space="preserve">
     <value>If the server does not specifically reject IPv6, IPAddress.IPv6Any is preferred over IPAddress.Any usage for safety and performance reasons. See https://aka.ms/aspnetcore-warnings/ASP0028 for more details.</value>
   </data>
+  <data name="Analyzer_UseCreateHostBuilderInsteadOfCreateWebHostBuilder_Title" xml:space="preserve">
+    <value>Use Host.CreateDefaultBuilder instead of WebHost.CreateDefaultBuilder</value>
+  </data>
+  <data name="Analyzer_UseCreateHostBuilderInsteadOfCreateWebHostBuilder_Message" xml:space="preserve">
+    <value>WebHost is deprecated. Use Host.CreateDefaultBuilder and ConfigureWebHostDefaults instead.</value>
+  </data>
 </root>

src/Framework/AspNetCoreAnalyzers/src/Analyzers/WebApplicationBuilder/UseCreateHostBuilderInsteadOfCreateWebHostBuilderAnalyzer.cs

@@ -0,0 +1,109 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Immutable;
+using System.Linq;
+using Microsoft.AspNetCore.App.Analyzers.Infrastructure;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Operations;
+
+namespace Microsoft.AspNetCore.Analyzers.WebApplicationBuilder;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class UseCreateHostBuilderInsteadOfCreateWebHostBuilderAnalyzer : DiagnosticAnalyzer
+{
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = ImmutableArray.Create(
+        DiagnosticDescriptors.UseCreateHostBuilderInsteadOfCreateWebHostBuilder
+    );
+
+    public override void Initialize(AnalysisContext context)
+    {
+        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
+        context.EnableConcurrentExecution();
+        context.RegisterCompilationStartAction(context =>
+        {
+            var compilation = context.Compilation;
+            var wellKnownTypes = WellKnownTypes.GetOrCreate(compilation);
+
+            context.RegisterOperationAction(context =>
+            {
+                var invocation = (IInvocationOperation)context.Operation;
+                var targetMethod = invocation.TargetMethod;
+
+                // Check if this is WebHost.CreateDefaultBuilder
+                if (IsWebHostCreateDefaultBuilderCall(targetMethod))
+                {
+                    var diagnostic = Diagnostic.Create(
+                        DiagnosticDescriptors.UseCreateHostBuilderInsteadOfCreateWebHostBuilder,
+                        invocation.Syntax.GetLocation()
+                    );
+                    context.ReportDiagnostic(diagnostic);
+                }
+            }, OperationKind.Invocation);
+
+            context.RegisterSyntaxNodeAction(context =>
+            {
+                var methodDeclaration = (MethodDeclarationSyntax)context.Node;
+                var semantic = context.SemanticModel;
+                var symbol = semantic.GetDeclaredSymbol(methodDeclaration);
+                
+                // Check if this method returns IWebHostBuilder
+                if (symbol != null && IsWebHostBuilderReturnType(symbol))
+                {
+                    // Check if the method body contains WebHost.CreateDefaultBuilder
+                    if (ContainsWebHostCreateDefaultBuilder(methodDeclaration))
+                    {
+                        var diagnostic = Diagnostic.Create(
+                            DiagnosticDescriptors.UseCreateHostBuilderInsteadOfCreateWebHostBuilder,
+                            methodDeclaration.ReturnType.GetLocation()
+                        );
+                        context.ReportDiagnostic(diagnostic);
+                    }
+                }
+            }, SyntaxKind.MethodDeclaration);
+        });
+    }
+
+    private static bool IsWebHostCreateDefaultBuilderCall(IMethodSymbol method)
+    {
+        // Check if this is WebHost.CreateDefaultBuilder (not other WebHost methods)
+        if (method.Name == "CreateDefaultBuilder" && 
+            method.ContainingType?.Name == "WebHost" &&
+            method.ContainingType?.ContainingNamespace?.ToDisplayString() == "Microsoft.AspNetCore")
+        {
+            return true;
+        }
+
+        return false;
+    }
+
+    private static bool IsWebHostBuilderReturnType(IMethodSymbol method)
+    {
+        // Check if the return type is IWebHostBuilder
+        var returnType = method.ReturnType;
+        return returnType.Name == "IWebHostBuilder" && 
+               returnType.ContainingNamespace?.ToDisplayString() == "Microsoft.AspNetCore.Hosting";
+    }
+
+    private static bool ContainsWebHostCreateDefaultBuilder(MethodDeclarationSyntax methodDeclaration)
+    {
+        // Check if the method contains WebHost.CreateDefaultBuilder calls
+        var descendants = methodDeclaration.DescendantNodes().OfType<InvocationExpressionSyntax>();
+        
+        foreach (var invocation in descendants)
+        {
+            if (invocation.Expression is MemberAccessExpressionSyntax memberAccess &&
+                memberAccess.Expression is IdentifierNameSyntax identifier &&
+                identifier.Identifier.ValueText == "WebHost" &&
+                memberAccess.Name.Identifier.ValueText == "CreateDefaultBuilder")
+            {
+                return true;
+            }
+        }
+        
+        return false;
+    }
+}