Add codefixer and completion provider to install OpenAPI package from extension methods

src/Analyzers/Microsoft.AspNetCore.Analyzer.Testing/src/DiagnosticProject.cs

@@ -28,7 +28,7 @@ public class DiagnosticProject
     private static readonly ICompilationAssemblyResolver _assemblyResolver = new AppBaseCompilationAssemblyResolver();
     private static readonly Dictionary<Assembly, Solution> _solutionCache = new Dictionary<Assembly, Solution>();
 
-    public static Project Create(Assembly testAssembly, string[] sources, Func<Workspace> workspaceFactory = null, Type analyzerReference = null)
+    public static Project Create(Assembly testAssembly, string[] sources, Func<Workspace> workspaceFactory = null, Type[] analyzerReferences = null)
     {
         Solution solution;
         lock (_solutionCache)
@@ -50,11 +50,14 @@ public static Project Create(Assembly testAssembly, string[] sources, Func<Works
                     }
                 }
 
-                if (analyzerReference != null)
+                if (analyzerReferences != null)
                 {
-                    solution = solution.AddAnalyzerReference(
-                        projectId,
-                        new AnalyzerFileReference(analyzerReference.Assembly.Location, AssemblyLoader.Instance));
+                    foreach (var analyzerReference in analyzerReferences)
+                    {
+                        solution = solution.AddAnalyzerReference(
+                            projectId,
+                            new AnalyzerFileReference(analyzerReference.Assembly.Location, AssemblyLoader.Instance));
+                    }
                 }
 
                 _solutionCache.Add(testAssembly, solution);

src/Framework/AspNetCoreAnalyzers/src/CodeFixes/Dependencies/AddPackageFixer.cs

@@ -0,0 +1,126 @@
+// 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.Composition;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.App.Analyzers.Infrastructure;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.ExternalAccess.AspNetCore.AddPackage;
+
+namespace Microsoft.AspNetCore.Analyzers.Dependencies;
+
+/// <summary>
+/// This fixer uses Roslyn's AspNetCoreAddPackageCodeAction to support providing a code fix for a missing
+/// package based on APIs defined in that package that are called in user code. This fixer is particularly
+/// helpful for providing guidance to users on how to add a missing package when they are using an extension
+/// method on well-known types like `IServiceCollection` and `IApplicationBuilder`.
+/// </summary>
+/// <remarks>
+/// This class is not sealed to support mocking of the virtual method `TryCreateCodeActionAsync` in unit tests.
+/// </remarks>
+[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(AddPackageFixer)), Shared]
+public class AddPackageFixer : CodeFixProvider
+{
+    public override async Task RegisterCodeFixesAsync(CodeFixContext context)
+    {
+        var root = await context.Document.GetSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);
+        if (root == null)
+        {
+            return;
+        }
+
+        var semanticModel = await context.Document.GetSemanticModelAsync(context.CancellationToken).ConfigureAwait(false);
+        if (semanticModel == null)
+        {
+            return;
+        }
+
+        var wellKnownTypes = WellKnownTypes.GetOrCreate(semanticModel.Compilation);
+        var wellKnownExtensionMethodCache = ExtensionMethodsCache.ConstructFromWellKnownTypes(wellKnownTypes);
+
+        // Diagnostics are already filtered by FixableDiagnosticIds values.
+        foreach (var diagnostic in context.Diagnostics)
+        {
+            var location = diagnostic.Location.SourceSpan;
+            var node = root.FindNode(location);
+            if (node == null)
+            {
+                return;
+            }
+            var methodName = node is IdentifierNameSyntax identifier ? identifier.Identifier.Text : null;
+            if (methodName == null)
+            {
+                return;
+            }
+
+            if (node.Parent is not MemberAccessExpressionSyntax)
+            {
+                return;
+            }
+
+            var symbol = semanticModel.GetSymbolInfo(((MemberAccessExpressionSyntax)node.Parent).Expression).Symbol;
+            var symbolType = symbol switch
+            {
+                IMethodSymbol methodSymbol => methodSymbol.ReturnType,
+                IPropertySymbol propertySymbol => propertySymbol.Type,
+                ILocalSymbol localSymbol => localSymbol.Type,
+                _ => null
+            };
+
+            if (symbolType == null)
+            {
+                return;
+            }
+
+            var targetThisAndExtensionMethod = new ThisAndExtensionMethod(symbolType, methodName);
+            if (wellKnownExtensionMethodCache.TryGetValue(targetThisAndExtensionMethod, out var packageSourceAndNamespace))
+            {
+                var position = diagnostic.Location.SourceSpan.Start;
+                var packageInstallData = new AspNetCoreInstallPackageData(
+                    packageSource: null,
+                    packageName: packageSourceAndNamespace.packageName,
+                    packageVersionOpt: null,
+                    packageNamespaceName: packageSourceAndNamespace.namespaceName);
+                var codeAction = await TryCreateCodeActionAsync(
+                    context.Document,
+                    position,
+                    packageInstallData,
+                    context.CancellationToken);
+
+                if (codeAction != null)
+                {
+                    context.RegisterCodeFix(codeAction, diagnostic);
+                }
+            }
+
+        }
+    }
+
+    public sealed override FixAllProvider GetFixAllProvider() => WellKnownFixAllProviders.BatchFixer;
+
+    /// <example>
+    /// 'IServiceCollection' does not contain a definition for 'AddOpenApi' and no accessible extension method 'AddOpenApi' accepting
+    /// a first argument of type 'IServiceCollection' could be found (are you missing a using directive or an assembly reference?).
+    /// </example>
+    public override ImmutableArray<string> FixableDiagnosticIds { get; } = ["CS1061"];
+
+    internal virtual async Task<CodeAction?> TryCreateCodeActionAsync(
+        Document document,
+        int position,
+        AspNetCoreInstallPackageData packageInstallData,
+        CancellationToken cancellationToken)
+    {
+        var codeAction = await AspNetCoreAddPackageCodeAction.TryCreateCodeActionAsync(
+            document,
+            position,
+            packageInstallData,
+            cancellationToken);
+
+        return codeAction;
+    }
+}

src/Framework/AspNetCoreAnalyzers/src/CodeFixes/Dependencies/ExtensionMethodsCache.cs

@@ -0,0 +1,24 @@
+// 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.Generic;
+using Microsoft.AspNetCore.Analyzers;
+using Microsoft.AspNetCore.App.Analyzers.Infrastructure;
+
+internal static class ExtensionMethodsCache
+{
+    public static Dictionary<ThisAndExtensionMethod, PackageSourceAndNamespace> ConstructFromWellKnownTypes(WellKnownTypes wellKnownTypes)
+    {
+        return new()
+        {
+            {
+                new(wellKnownTypes.Get(WellKnownTypeData.WellKnownType.Microsoft_Extensions_DependencyInjection_IServiceCollection), "AddOpenApi"),
+                new("Microsoft.AspNetCore.OpenApi", "Microsoft.Extensions.DependencyInjection")
+            },
+            {
+                new(wellKnownTypes.Get(WellKnownTypeData.WellKnownType.Microsoft_AspNetCore_Builder_WebApplication), "MapOpenApi"),
+                new("Microsoft.AspNetCore.OpenApi", "Microsoft.AspNetCore.Builder")
+            }
+        };
+    }
+}

src/Framework/AspNetCoreAnalyzers/src/CodeFixes/Dependencies/ExtensionMethodsCompletionProvider.cs

@@ -0,0 +1,118 @@
+// 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.Generic;
+using System.Composition;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.App.Analyzers.Infrastructure;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Completion;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+
+namespace Microsoft.AspNetCore.Analyzers.RouteEmbeddedLanguage;
+
+/// <summary>
+/// This completion provider expands the completion list of target symbols defined in the
+/// ExtensionMethodsCache to include extension methods that can be invoked on the target
+/// type that are defined in auxillary packages. This completion provider is designed to be
+/// used in conjunction with the `AddPackageFixer` to recommend adding the missing packages
+/// extension methods are defined in.
+/// </summary>
+[ExportCompletionProvider(nameof(ExtensionMethodsCompletionProvider), LanguageNames.CSharp)]
+[Shared]
+public sealed class ExtensionMethodsCompletionProvider : CompletionProvider
+{
+    public override async Task ProvideCompletionsAsync(CompletionContext context)
+    {
+        if (!context.Document.SupportsSemanticModel)
+        {
+            return;
+        }
+
+        var root = await context.Document.GetSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);
+        if (root == null)
+        {
+            return;
+        }
+
+        var span = context.CompletionListSpan;
+        var token = root.FindToken(span.Start);
+        if (token.Parent == null)
+        {
+            return;
+        }
+
+        var semanticModel = await context.Document.GetSemanticModelAsync(context.CancellationToken).ConfigureAwait(false);
+        if (semanticModel == null)
+        {
+            return;
+        }
+
+        var wellKnownTypes = WellKnownTypes.GetOrCreate(semanticModel.Compilation);
+        var wellKnownExtensionMethodCache = ExtensionMethodsCache.ConstructFromWellKnownTypes(wellKnownTypes);
+
+        // We find the nearest member access expression to the adjacent expression to resolve the
+        // target type of the extension method that the user is invoking. For example, `app.` should
+        // allow us to resolve to a `WebApplication` instance and `builder.Services.Add` should resolve
+        // to an `IServiceCollection`.
+        var nearestMemberAccessExpression = FindNearestMemberAccessExpression(token.Parent);
+        if (nearestMemberAccessExpression is not null && nearestMemberAccessExpression is MemberAccessExpressionSyntax memberAccess)
+        {
+            var symbol = semanticModel.GetSymbolInfo(memberAccess.Expression);
+            var symbolType = symbol.Symbol switch
+            {
+                IMethodSymbol methodSymbol => methodSymbol.ReturnType,
+                IPropertySymbol propertySymbol => propertySymbol.Type,
+                ILocalSymbol localSymbol => localSymbol.Type,
+                _ => null
+            };
+
+            var matchingExtensionMethods = wellKnownExtensionMethodCache.Where(pair => IsMatchingExtensionMethod(pair, symbolType, token));
+            foreach (var item in matchingExtensionMethods)
+            {
+                context.CompletionListSpan = span;
+                context.AddItem(CompletionItem.Create(
+                    displayText: item.Key.ExtensionMethod,
+                    sortText: item.Key.ExtensionMethod,
+                    filterText: item.Key.ExtensionMethod
+                ));
+            }
+        }
+    }
+
+    private static SyntaxNode? FindNearestMemberAccessExpression(SyntaxNode? node)
+    {
+        var current = node;
+        while (current != null)
+        {
+            if (current?.IsKind(SyntaxKind.SimpleMemberAccessExpression) ?? false)
+            {
+                return current;
+            }
+
+            current = current?.Parent;
+        }
+
+        return null;
+    }
+
+    private static bool IsMatchingExtensionMethod(
+        KeyValuePair<ThisAndExtensionMethod, PackageSourceAndNamespace> pair,
+        ISymbol? symbolType,
+        SyntaxToken token)
+    {
+        if (symbolType is null)
+        {
+            return false;
+        }
+
+        // If the token that we are parsing is some sort of identifier, this indicates that the user
+        // has triggered a completion with characters already inserted into the invocation (e.g. `builder.Services.Ad$$).
+        // In this case, we only want to provide completions that match the characters that have been inserted.
+        var isIdentifierToken = token.IsKind(SyntaxKind.IdentifierName) || token.IsKind(SyntaxKind.IdentifierToken);
+        return SymbolEqualityComparer.Default.Equals(pair.Key.ThisType, symbolType) &&
+            (!isIdentifierToken || pair.Key.ExtensionMethod.Contains(token.ValueText));
+    }
+}

src/Framework/AspNetCoreAnalyzers/src/CodeFixes/Dependencies/PackageSourceAndNamespace.cs

@@ -0,0 +1,6 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.Analyzers;
+
+internal record struct PackageSourceAndNamespace(string packageName, string namespaceName);

src/Framework/AspNetCoreAnalyzers/src/CodeFixes/Dependencies/ThisAndExtensionMethod.cs

@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.CodeAnalysis;
+
+namespace Microsoft.AspNetCore.Analyzers;
+
+internal readonly struct ThisAndExtensionMethod(ITypeSymbol thisType, string extensionMethod)
+{
+    public ITypeSymbol ThisType { get; } = thisType;
+    public string ExtensionMethod { get; } = extensionMethod;
+
+    public override bool Equals(object obj)
+    {
+        return obj is ThisAndExtensionMethod other &&
+            SymbolEqualityComparer.Default.Equals(ThisType, other.ThisType) &&
+            ExtensionMethod == other.ExtensionMethod;
+    }
+
+    public override int GetHashCode()
+    {
+        return HashCode.Combine(ThisType, ExtensionMethod);
+    }
+}

src/Framework/AspNetCoreAnalyzers/src/CodeFixes/Microsoft.AspNetCore.App.CodeFixes.csproj

@@ -22,4 +22,12 @@
     <ProjectReference Include="..\Analyzers\Microsoft.AspNetCore.App.Analyzers.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <InternalsVisibleTo Include="Microsoft.AspNetCore.App.Analyzers.Test" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Compile Include="$(RepoRoot)\src\Shared\HashCode.cs" />
+  </ItemGroup>
+
 </Project>