Handle adding using directives if needed

src/CommunityToolkit.Mvvm.CodeFixers/UsePartialPropertyForSemiAutoPropertyCodeFixer.cs

@@ -15,6 +15,7 @@
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Editing;
 using Microsoft.CodeAnalysis.Formatting;
+using Microsoft.CodeAnalysis.Simplification;
 using Microsoft.CodeAnalysis.Text;
 using static CommunityToolkit.Mvvm.SourceGenerators.Diagnostics.DiagnosticDescriptors;
 using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
@@ -32,9 +33,9 @@ public sealed class UsePartialPropertyForSemiAutoPropertyCodeFixer : CodeFixProv
     public override ImmutableArray<string> FixableDiagnosticIds { get; } = ImmutableArray.Create(UseObservablePropertyOnSemiAutoPropertyId);
 
     /// <inheritdoc/>
-    public override FixAllProvider? GetFixAllProvider()
+    public override Microsoft.CodeAnalysis.CodeFixes.FixAllProvider? GetFixAllProvider()
     {
-        return WellKnownFixAllProviders.BatchFixer;
+        return new FixAllProvider();
     }
 
     /// <inheritdoc/>
@@ -43,16 +44,31 @@ public override async Task RegisterCodeFixesAsync(CodeFixContext context)
         Diagnostic diagnostic = context.Diagnostics[0];
         TextSpan diagnosticSpan = context.Span;
 
+        // This code fixer needs the semantic model, so check that first
+        if (!context.Document.SupportsSemanticModel)
+        {
+            return;
+        }
+
         SyntaxNode? root = await context.Document.GetSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);
 
         // Get the property declaration from the target diagnostic
         if (root!.FindNode(diagnosticSpan) is PropertyDeclarationSyntax propertyDeclaration)
         {
+            // Get the semantic model, as we need to resolve symbols
+            SemanticModel semanticModel = (await context.Document.GetSemanticModelAsync(context.CancellationToken).ConfigureAwait(false))!;
+
+            // Make sure we can resolve the [ObservableProperty] attribute (as we want to add it in the fixed code)
+            if (semanticModel.Compilation.GetTypeByMetadataName("CommunityToolkit.Mvvm.ComponentModel.ObservablePropertyAttribute") is not INamedTypeSymbol observablePropertySymbol)
+            {
+                return;
+            }
+
             // Register the code fix to update the semi-auto property to a partial property
             context.RegisterCodeFix(
                 CodeAction.Create(
                     title: "Use a partial property",
-                    createChangedDocument: token => ConvertToPartialProperty(context.Document, root, propertyDeclaration),
+                    createChangedDocument: token => ConvertToPartialProperty(context.Document, root, propertyDeclaration, observablePropertySymbol),
                     equivalenceKey: "Use a partial property"),
                 diagnostic);
         }
@@ -64,14 +80,47 @@ public override async Task RegisterCodeFixesAsync(CodeFixContext context)
     /// <param name="document">The original document being fixed.</param>
     /// <param name="root">The original tree root belonging to the current document.</param>
     /// <param name="propertyDeclaration">The <see cref="PropertyDeclarationSyntax"/> for the property being updated.</param>
+    /// <param name="observablePropertySymbol">The <see cref="INamedTypeSymbol"/> for <c>[ObservableProperty]</c>.</param>
     /// <returns>An updated document with the applied code fix, and <paramref name="propertyDeclaration"/> being replaced with a partial property.</returns>
-    private static async Task<Document> ConvertToPartialProperty(Document document, SyntaxNode root, PropertyDeclarationSyntax propertyDeclaration)
+    private static async Task<Document> ConvertToPartialProperty(
+        Document document,
+        SyntaxNode root,
+        PropertyDeclarationSyntax propertyDeclaration,
+        INamedTypeSymbol observablePropertySymbol)
     {
         await Task.CompletedTask;
 
-        // Prepare the [ObservableProperty] attribute, which is always inserted first
-        AttributeListSyntax observablePropertyAttributeList = AttributeList(SingletonSeparatedList(Attribute(IdentifierName("ObservableProperty"))));
+        SyntaxGenerator syntaxGenerator = SyntaxGenerator.GetGenerator(document);
+
+        // Create the attribute syntax for the new [ObservableProperty] attribute. Also
+        // annotate it to automatically add using directives to the document, if needed.
+        SyntaxNode attributeTypeSyntax = syntaxGenerator.TypeExpression(observablePropertySymbol).WithAdditionalAnnotations(Simplifier.AddImportsAnnotation);
+        AttributeListSyntax observablePropertyAttributeList = (AttributeListSyntax)syntaxGenerator.Attribute(attributeTypeSyntax);
 
+        // Create an editor to perform all mutations
+        SyntaxEditor syntaxEditor = new(root, document.Project.Solution.Workspace.Services);
+
+        ConvertToPartialProperty(
+            propertyDeclaration,
+            observablePropertyAttributeList,
+            syntaxEditor);
+
+        // Create the new document with the single change
+        return document.WithSyntaxRoot(syntaxEditor.GetChangedRoot());
+    }
+
+    /// <summary>
+    /// Applies the code fix to a target identifier and returns an updated document.
+    /// </summary>
+    /// <param name="propertyDeclaration">The <see cref="PropertyDeclarationSyntax"/> for the property being updated.</param>
+    /// <param name="observablePropertyAttributeList">The <see cref="AttributeListSyntax"/> with the attribute to add.</param>
+    /// <param name="syntaxEditor">The <see cref="SyntaxEditor"/> instance to use.</param>
+    /// <returns>An updated document with the applied code fix, and <paramref name="propertyDeclaration"/> being replaced with a partial property.</returns>
+    private static void ConvertToPartialProperty(
+        PropertyDeclarationSyntax propertyDeclaration,
+        AttributeListSyntax observablePropertyAttributeList,
+        SyntaxEditor syntaxEditor)
+    {
         // Start setting up the updated attribute lists
         SyntaxList<AttributeListSyntax> attributeLists = propertyDeclaration.AttributeLists;
 
@@ -120,10 +169,7 @@ private static async Task<Document> ConvertToPartialProperty(Document document,
                 .WithAdditionalAnnotations(Formatter.Annotation)
             ])).WithTrailingTrivia(propertyDeclaration.AccessorList.GetTrailingTrivia()));
 
-        // Create an editor to perform all mutations
-        SyntaxEditor editor = new(root, document.Project.Solution.Workspace.Services);
-
-        editor.ReplaceNode(propertyDeclaration, updatedPropertyDeclaration);
+        syntaxEditor.ReplaceNode(propertyDeclaration, updatedPropertyDeclaration);
 
         // Find the parent type for the property
         TypeDeclarationSyntax typeDeclaration = propertyDeclaration.FirstAncestorOrSelf<TypeDeclarationSyntax>()!;
@@ -132,10 +178,61 @@ private static async Task<Document> ConvertToPartialProperty(Document document,
         // If we created it separately and replaced it, the whole tree would also be replaced, and we'd lose the new property.
         if (!typeDeclaration.Modifiers.Any(SyntaxKind.PartialKeyword))
         {
-            editor.ReplaceNode(typeDeclaration, static (node, generator) => generator.WithModifiers(node, generator.GetModifiers(node).WithPartial(true)));
+            syntaxEditor.ReplaceNode(typeDeclaration, static (node, generator) => generator.WithModifiers(node, generator.GetModifiers(node).WithPartial(true)));
         }
+    }
 
-        return document.WithSyntaxRoot(editor.GetChangedRoot());
+    /// <summary>
+    /// A custom <see cref="FixAllProvider"/> with the logic from <see cref="UsePartialPropertyForSemiAutoPropertyCodeFixer"/>.
+    /// </summary>
+    private sealed class FixAllProvider : DocumentBasedFixAllProvider
+    {
+        /// <inheritdoc/>
+        protected override async Task<Document?> FixAllAsync(FixAllContext fixAllContext, Document document, ImmutableArray<Diagnostic> diagnostics)
+        {
+            // Get the semantic model, as we need to resolve symbols
+            if (await document.GetSemanticModelAsync(fixAllContext.CancellationToken).ConfigureAwait(false) is not SemanticModel semanticModel)
+            {
+                return document;
+            }
+
+            // Make sure we can resolve the [ObservableProperty] attribute here as well
+            if (semanticModel.Compilation.GetTypeByMetadataName("CommunityToolkit.Mvvm.ComponentModel.ObservablePropertyAttribute") is not INamedTypeSymbol observablePropertySymbol)
+            {
+                return document;
+            }
+
+            // Get the document root (this should always succeed)
+            if (await document.GetSyntaxRootAsync(fixAllContext.CancellationToken).ConfigureAwait(false) is not SyntaxNode root)
+            {
+                return document;
+            }
+
+            SyntaxGenerator syntaxGenerator = SyntaxGenerator.GetGenerator(document);
+
+            // Create the attribute syntax for the new [ObservableProperty] attribute here too
+            SyntaxNode attributeTypeSyntax = syntaxGenerator.TypeExpression(observablePropertySymbol).WithAdditionalAnnotations(Simplifier.AddImportsAnnotation);
+            AttributeListSyntax observablePropertyAttributeList = (AttributeListSyntax)syntaxGenerator.Attribute(attributeTypeSyntax);
+
+            // Create an editor to perform all mutations (across all edits in the file)
+            SyntaxEditor syntaxEditor = new(root, fixAllContext.Solution.Services);
+
+            foreach (Diagnostic diagnostic in diagnostics)
+            {
+                // Get the current property declaration for the diagnostic
+                if (root.FindNode(diagnostic.Location.SourceSpan) is not PropertyDeclarationSyntax propertyDeclaration)
+                {
+                    continue;
+                }
+
+                ConvertToPartialProperty(
+                    propertyDeclaration,
+                    observablePropertyAttributeList,
+                    syntaxEditor);
+            }
+
+            return document.WithSyntaxRoot(syntaxEditor.GetChangedRoot());
+        }
     }
 }
 

tests/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4120.UnitTests/Test_UseObservablePropertyOnSemiAutoPropertyCodeFixer.cs

@@ -127,6 +127,57 @@ public partial class SampleViewModel : ObservableObject
         await test.RunAsync();
     }
 
+    [TestMethod]
+    public async Task SimpleProperty_WithMissingUsingDirective()
+    {
+        string original = """
+            namespace MyApp;
+
+            public class SampleViewModel : CommunityToolkit.Mvvm.ComponentModel.ObservableObject
+            {
+                public string Name
+                {
+                    get => field;
+                    set => SetProperty(ref field, value);
+                }
+            }
+            """;
+
+        string @fixed = """
+            using CommunityToolkit.Mvvm.ComponentModel;
+
+            namespace MyApp;
+
+            public partial class SampleViewModel : CommunityToolkit.Mvvm.ComponentModel.ObservableObject
+            {
+                [ObservableProperty]
+                public partial string Name { get; set; }
+            }
+            """;
+
+        CSharpCodeFixTest test = new(LanguageVersion.Preview)
+        {
+            TestCode = original,
+            FixedCode = @fixed,
+            ReferenceAssemblies = ReferenceAssemblies.Net.Net80,
+        };
+
+        test.TestState.AdditionalReferences.Add(typeof(ObservableObject).Assembly);
+        test.ExpectedDiagnostics.AddRange(new[]
+        {
+            // /0/Test0.cs(5,19): info MVVMTK0056: The semi-auto property MyApp.SampleViewModel.Name can be converted to a partial property using [ObservableProperty], which is recommended (doing so makes the code less verbose and results in more optimized code)
+            CSharpCodeFixVerifier.Diagnostic().WithSpan(5, 19, 5, 23).WithArguments("MyApp.SampleViewModel", "Name"),
+        });
+
+        test.FixedState.ExpectedDiagnostics.AddRange(new[]
+        {
+            // /0/Test0.cs(8,27): error CS9248: Partial property 'SampleViewModel.Name' must have an implementation part.
+            DiagnosticResult.CompilerError("CS9248").WithSpan(8, 27, 8, 31).WithArguments("MyApp.SampleViewModel.Name"),
+        });
+
+        await test.RunAsync();
+    }
+
     [TestMethod]
     public async Task SimpleProperty_WithLeadingTrivia()
     {
@@ -582,6 +633,87 @@ public partial class SampleViewModel : ObservableObject
         await test.RunAsync();
     }
 
+    [TestMethod]
+    public async Task SimpleProperty_Multiple_WithMissingUsingDirective()
+    {
+        string original = """
+            namespace MyApp;
+
+            public partial class SampleViewModel : CommunityToolkit.Mvvm.ComponentModel.ObservableObject
+            {
+                public string FirstName
+                {
+                    get => field;
+                    set => SetProperty(ref field, value);
+                }
+
+                public string LastName
+                {
+                    get => field;
+                    set => SetProperty(ref field, value);
+                }
+
+                public string PhoneNumber
+                {
+                    get;
+                    set => SetProperty(ref field, value);
+                }
+            }
+            """;
+
+        string @fixed = """
+            using CommunityToolkit.Mvvm.ComponentModel;
+
+            namespace MyApp;
+
+            public partial class SampleViewModel : CommunityToolkit.Mvvm.ComponentModel.ObservableObject
+            {
+                [ObservableProperty]
+                public partial string FirstName { get; set; }
+
+                [ObservableProperty]
+                public partial string LastName { get; set; }
+
+                [ObservableProperty]
+                public partial string PhoneNumber { get; set; }
+            }
+            """;
+
+        CSharpCodeFixTest test = new(LanguageVersion.Preview)
+        {
+            TestCode = original,
+            FixedCode = @fixed,
+            ReferenceAssemblies = ReferenceAssemblies.Net.Net80,
+        };
+
+        test.TestState.AdditionalReferences.Add(typeof(ObservableObject).Assembly);
+        test.ExpectedDiagnostics.AddRange(new[]
+        {
+            // /0/Test0.cs(5,19): info MVVMTK0056: The semi-auto property MyApp.SampleViewModel.FirstName can be converted to a partial property using [ObservableProperty], which is recommended (doing so makes the code less verbose and results in more optimized code)
+            CSharpCodeFixVerifier.Diagnostic().WithSpan(5, 19, 5, 28).WithArguments("MyApp.SampleViewModel", "FirstName"),
+
+            // /0/Test0.cs(11,19): info MVVMTK0056: The semi-auto property MyApp.SampleViewModel.LastName can be converted to a partial property using [ObservableProperty], which is recommended (doing so makes the code less verbose and results in more optimized code)
+            CSharpCodeFixVerifier.Diagnostic().WithSpan(11, 19, 11, 27).WithArguments("MyApp.SampleViewModel", "LastName"),
+
+            // /0/Test0.cs(17,19): info MVVMTK0056: The semi-auto property MyApp.SampleViewModel.PhoneNumber can be converted to a partial property using [ObservableProperty], which is recommended (doing so makes the code less verbose and results in more optimized code)
+            CSharpCodeFixVerifier.Diagnostic().WithSpan(17, 19, 17, 30).WithArguments("MyApp.SampleViewModel", "PhoneNumber"),
+        });
+
+        test.FixedState.ExpectedDiagnostics.AddRange(new[]
+        {
+            // /0/Test0.cs(8,27): error CS9248: Partial property 'SampleViewModel.FirstName' must have an implementation part.
+            DiagnosticResult.CompilerError("CS9248").WithSpan(8, 27, 8, 36).WithArguments("MyApp.SampleViewModel.FirstName"),
+
+            // /0/Test0.cs(11,27): error CS9248: Partial property 'SampleViewModel.LastName' must have an implementation part.
+            DiagnosticResult.CompilerError("CS9248").WithSpan(11, 27, 11, 35).WithArguments("MyApp.SampleViewModel.LastName"),
+
+            // /0/Test0.cs(14,27): error CS9248: Partial property 'SampleViewModel.PhoneNumber' must have an implementation part.
+            DiagnosticResult.CompilerError("CS9248").WithSpan(14, 27, 14, 38).WithArguments("MyApp.SampleViewModel.PhoneNumber"),
+        });
+
+        await test.RunAsync();
+    }
+
     [TestMethod]
     public async Task SimpleProperty_WithinPartialType_Multiple_MixedScenario()
     {