Add MVVM dependency graph notifications

src/CommunityToolkit.Mvvm.SourceGenerators/AnalyzerReleases.Unshipped.md

@@ -1,2 +1,9 @@
 ; Unshipped analyzer release
 ; https://github.com/dotnet/roslyn-analyzers/blob/main/src/Microsoft.CodeAnalysis.Analyzers/ReleaseTrackingAnalyzers.Help.md
+
+### New Rules
+Rule ID | Category | Severity | Notes
+--------|----------|----------|-------
+MVVMTK0057 | CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator | Error | Invalid source name for [DependsOn]
+MVVMTK0058 | CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator | Error | Dependency cycle for [DependsOn]
+MVVMTK0059 | CommunityToolkit.Mvvm.SourceGenerators.ObservablePropertyGenerator | Error | Invalid sub-property source for [DependsOn]

src/CommunityToolkit.Mvvm.SourceGenerators/CommunityToolkit.Mvvm.SourceGenerators.projitems

@@ -25,6 +25,7 @@
   <ItemGroup>
     <Compile Include="$(MSBuildThisFileDirectory)ComponentModel\INotifyPropertyChangedGenerator.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ComponentModel\Models\AttributeInfo.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)ComponentModel\Models\ChildPropertyChangedSubscriptionInfo.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ComponentModel\Models\INotifyPropertyChangedInfo.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ComponentModel\Models\ObservableRecipientInfo.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ComponentModel\Models\PropertyInfo.cs" />
@@ -113,4 +114,4 @@
   <ItemGroup>
     <None Include="$(MSBuildThisFileDirectory)CommunityToolkit.Mvvm.SourceGenerators.props" />
   </ItemGroup>
-</Project>
+</Project>

src/CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/Models/ChildPropertyChangedSubscriptionInfo.cs

@@ -0,0 +1,16 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using CommunityToolkit.Mvvm.SourceGenerators.Helpers;
+
+namespace CommunityToolkit.Mvvm.SourceGenerators.ComponentModel.Models;
+
+/// <summary>
+/// A model representing generated child <c>PropertyChanged</c> forwarding for an observable property.
+/// </summary>
+/// <param name="PropertyChangedNames">The dependent property names to notify when the child instance changes.</param>
+/// <param name="NotifiedCommandNames">The dependent command names to notify when the child instance changes.</param>
+internal sealed record ChildPropertyChangedSubscriptionInfo(
+    EquatableArray<string> PropertyChangedNames,
+    EquatableArray<string> NotifiedCommandNames);

src/CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/Models/PropertyInfo.cs

@@ -22,6 +22,7 @@ namespace CommunityToolkit.Mvvm.SourceGenerators.ComponentModel.Models;
 /// <param name="PropertyChangingNames">The sequence of property changing properties to notify.</param>
 /// <param name="PropertyChangedNames">The sequence of property changed properties to notify.</param>
 /// <param name="NotifiedCommandNames">The sequence of commands to notify.</param>
+/// <param name="ChildPropertyChangedSubscriptions">The child property changed subscriptions to generate.</param>
 /// <param name="NotifyPropertyChangedRecipients">Whether or not the generated property also broadcasts changes.</param>
 /// <param name="NotifyDataErrorInfo">Whether or not the generated property also validates its value.</param>
 /// <param name="IsOldPropertyValueDirectlyReferenced">Whether the old property value is being directly referenced.</param>
@@ -41,6 +42,7 @@ internal sealed record PropertyInfo(
     EquatableArray<string> PropertyChangingNames,
     EquatableArray<string> PropertyChangedNames,
     EquatableArray<string> NotifiedCommandNames,
+    EquatableArray<ChildPropertyChangedSubscriptionInfo> ChildPropertyChangedSubscriptions,
     bool NotifyPropertyChangedRecipients,
     bool NotifyDataErrorInfo,
     bool IsOldPropertyValueDirectlyReferenced,

src/CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/ObservablePropertyGenerator.cs

@@ -22,6 +22,16 @@ public sealed partial class ObservablePropertyGenerator : IIncrementalGenerator
     /// <inheritdoc/>
     public void Initialize(IncrementalGeneratorInitializationContext context)
     {
+        // Gather diagnostics for [DependsOn] declarations, including cases where no observable property is generated in the target type.
+        IncrementalValuesProvider<EquatableArray<DiagnosticInfo>> dependsOnDiagnostics =
+            context.SyntaxProvider
+            .ForAttributeWithMetadataName(
+                "CommunityToolkit.Mvvm.ComponentModel.DependsOnAttribute",
+                static (node, _) => node is PropertyDeclarationSyntax propertyDeclaration && propertyDeclaration.AttributeLists.Count > 0,
+                static (context, token) => Execute.GetDependsOnDiagnostics((IPropertySymbol)context.TargetSymbol, context.Attributes, token));
+
+        context.ReportDiagnostics(dependsOnDiagnostics);
+
         // Gather info for all annotated fields
         IncrementalValuesProvider<(HierarchyInfo Hierarchy, Result<PropertyInfo?> Info)> propertyInfoWithErrors =
             context.ForAttributeWithMetadataNameAndOptions(
@@ -86,6 +96,7 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
                 item.Properties
                 .Select(Execute.GetPropertySyntax)
                 .Concat(item.Properties.Select(Execute.GetOnPropertyChangeMethodsSyntax).SelectMany(static l => l))
+                .Concat(item.Properties.Select(Execute.GetChildPropertyChangedSubscriptionMembersSyntax).SelectMany(static l => l))
                 .ToImmutableArray();
 
             // Insert all members into the same partial type declaration

src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/DiagnosticDescriptors.cs

@@ -944,4 +944,52 @@ internal static class DiagnosticDescriptors
         isEnabledByDefault: true,
         description: "Semi-auto properties should be converted to partial properties using [ObservableProperty] when possible, which is recommended (doing so makes the code less verbose and results in more optimized code).",
         helpLinkUri: "https://aka.ms/mvvmtoolkit/errors/mvvmtk0056");
+
+    /// <summary>
+    /// Gets a <see cref="DiagnosticDescriptor"/> indicating when a <c>[DependsOn]</c> source property is invalid.
+    /// <para>
+    /// Format: <c>"The source property "{0}" for [DependsOn] has no valid match in type {1}"</c>.
+    /// </para>
+    /// </summary>
+    public static readonly DiagnosticDescriptor DependsOnInvalidSourceError = new DiagnosticDescriptor(
+        id: "MVVMTK0057",
+        title: "Invalid source name for [DependsOn]",
+        messageFormat: "The source property \"{0}\" for [DependsOn] has no valid match in type {1}",
+        category: typeof(ObservablePropertyGenerator).FullName,
+        defaultSeverity: DiagnosticSeverity.Error,
+        isEnabledByDefault: true,
+        description: "The source properties for [DependsOn] must be different accessible properties in the parent type.",
+        helpLinkUri: "https://aka.ms/mvvmtoolkit/errors/mvvmtk0057");
+
+    /// <summary>
+    /// Gets a <see cref="DiagnosticDescriptor"/> indicating when <c>[DependsOn]</c> declarations create a cycle.
+    /// <para>
+    /// Format: <c>"The [DependsOn] declaration for property "{0}" creates a dependency cycle in type {1}"</c>.
+    /// </para>
+    /// </summary>
+    public static readonly DiagnosticDescriptor DependsOnCycleError = new DiagnosticDescriptor(
+        id: "MVVMTK0058",
+        title: "Dependency cycle for [DependsOn]",
+        messageFormat: "The [DependsOn] declaration for property \"{0}\" creates a dependency cycle in type {1}",
+        category: typeof(ObservablePropertyGenerator).FullName,
+        defaultSeverity: DiagnosticSeverity.Error,
+        isEnabledByDefault: true,
+        description: "The dependency graph declared with [DependsOn] must not contain cycles.",
+        helpLinkUri: "https://aka.ms/mvvmtoolkit/errors/mvvmtk0058");
+
+    /// <summary>
+    /// Gets a <see cref="DiagnosticDescriptor"/> indicating when <c>[DependsOn(NotifyOnSubPropertyChanges = true)]</c> is used with an invalid source.
+    /// <para>
+    /// Format: <c>"The source property "{0}" for [DependsOn(NotifyOnSubPropertyChanges = true)] must be a generated observable property implementing INotifyPropertyChanged in type {1}"</c>.
+    /// </para>
+    /// </summary>
+    public static readonly DiagnosticDescriptor DependsOnInvalidSubPropertySourceError = new DiagnosticDescriptor(
+        id: "MVVMTK0059",
+        title: "Invalid sub-property source for [DependsOn]",
+        messageFormat: "The source property \"{0}\" for [DependsOn(NotifyOnSubPropertyChanges = true)] must be a generated observable property implementing INotifyPropertyChanged in type {1}",
+        category: typeof(ObservablePropertyGenerator).FullName,
+        defaultSeverity: DiagnosticSeverity.Error,
+        isEnabledByDefault: true,
+        description: "Sources for [DependsOn(NotifyOnSubPropertyChanges = true)] must be generated observable properties with a type implementing INotifyPropertyChanged.",
+        helpLinkUri: "https://aka.ms/mvvmtoolkit/errors/mvvmtk0059");
 }

src/CommunityToolkit.Mvvm/ComponentModel/Attributes/DependsOnAttribute.cs

@@ -0,0 +1,49 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Linq;
+
+namespace CommunityToolkit.Mvvm.ComponentModel;
+
+/// <summary>
+/// An attribute that can be used to declare dependencies for calculated properties.
+/// When this attribute is used on a property, generated observable properties listed
+/// in <see cref="PropertyNames"/> will also notify the annotated property when changed.
+/// </summary>
+/// <remarks>
+/// This attribute is processed by the MVVM Toolkit source generators.
+/// </remarks>
+[AttributeUsage(AttributeTargets.Property, AllowMultiple = true, Inherited = false)]
+public sealed class DependsOnAttribute : Attribute
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="DependsOnAttribute"/> class.
+    /// </summary>
+    /// <param name="propertyName">The name of the property this calculated property depends on.</param>
+    public DependsOnAttribute(string propertyName)
+    {
+        PropertyNames = new[] { propertyName };
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="DependsOnAttribute"/> class.
+    /// </summary>
+    /// <param name="propertyName">The name of the property this calculated property depends on.</param>
+    /// <param name="otherPropertyNames">The other property names this calculated property depends on.</param>
+    public DependsOnAttribute(string propertyName, params string[] otherPropertyNames)
+    {
+        PropertyNames = new[] { propertyName }.Concat(otherPropertyNames).ToArray();
+    }
+
+    /// <summary>
+    /// Gets the property names this calculated property depends on.
+    /// </summary>
+    public string[] PropertyNames { get; }
+
+    /// <summary>
+    /// Gets or sets whether changes from child <see cref="System.ComponentModel.INotifyPropertyChanged"/> instances should also notify dependents.
+    /// </summary>
+    public bool NotifyOnSubPropertyChanges { get; set; }
+}

tests/CommunityToolkit.Mvvm.SourceGenerators.UnitTests/Test_SourceGeneratorsCodegen.cs

@@ -230,6 +230,80 @@ partial class MyViewModel
         VerifyGenerateSources(source, new[] { new ObservablePropertyGenerator() }, ("MyApp.MyViewModel.g.cs", result));
     }
 
+    [TestMethod]
+    public void DependsOnGeneratedDependencyGraph_IncludesTransitiveNotificationsAndCommandInvalidation()
+    {
+        string source = """
+            using CommunityToolkit.Mvvm.ComponentModel;
+            using CommunityToolkit.Mvvm.Input;
+
+            namespace MyApp;
+
+            partial class MyViewModel : ObservableObject
+            {
+                [ObservableProperty]
+                private string? name;
+
+                [DependsOn(nameof(Name))]
+                public bool CanSave => !string.IsNullOrWhiteSpace(Name);
+
+                [DependsOn(nameof(CanSave))]
+                public string State => CanSave ? "Ready" : "Blocked";
+
+                [RelayCommand(CanExecute = nameof(CanSave))]
+                private void Save()
+                {
+                }
+            }
+            """;
+
+        VerifyGeneratedSourceContains(
+            source,
+            new IIncrementalGenerator[] { new ObservablePropertyGenerator(), new RelayCommandGenerator() },
+            "MyApp.MyViewModel.g.cs",
+            [
+                "OnPropertyChanged(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangedArgs.Name);",
+                "OnPropertyChanged(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangedArgs.CanSave);",
+                "OnPropertyChanged(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangedArgs.State);",
+                "SaveCommand.NotifyCanExecuteChanged();"
+            ]);
+    }
+
+    [TestMethod]
+    public void DependsOnGeneratedDependencyGraph_IncludesChildSubscriptionHelpers()
+    {
+        string source = """
+            using CommunityToolkit.Mvvm.ComponentModel;
+
+            namespace MyApp;
+
+            partial class ChildViewModel : ObservableObject
+            {
+                [ObservableProperty]
+                private string? name;
+            }
+
+            partial class MyViewModel : ObservableObject
+            {
+                [ObservableProperty]
+                private ChildViewModel? selectedItem;
+
+                [DependsOn(nameof(SelectedItem), NotifyOnSubPropertyChanges = true)]
+                public string? SelectedItemName => SelectedItem?.Name;
+            }
+            """;
+
+        VerifyGeneratedSourceContains(
+            source,
+            new[] { new ObservablePropertyGenerator() },
+            "MyApp.MyViewModel.g.cs",
+            [
+                "PropertyChanged +=",
+                "PropertyChanged -=",
+                "OnPropertyChanged(global::CommunityToolkit.Mvvm.ComponentModel.__Internals.__KnownINotifyPropertyChangedArgs.SelectedItemName);"
+            ]);
+    }
+
     [TestMethod]
     public void ObservablePropertyWithNonNullableUnconstrainedGenericType_EmitsMemberNotNullAttribute()
     {
@@ -3525,4 +3599,49 @@ from assembly in AppDomain.CurrentDomain.GetAssemblies()
         GC.KeepAlive(observableObjectType);
         GC.KeepAlive(validationAttributeType);
     }
+
+    /// <summary>
+    /// Generates sources and verifies that a generated file contains a set of snippets.
+    /// </summary>
+    /// <param name="source">The input source to process.</param>
+    /// <param name="generators">The generators to apply to the input syntax tree.</param>
+    /// <param name="filename">The generated filename to inspect.</param>
+    /// <param name="snippets">The snippets expected in the generated source.</param>
+    private static void VerifyGeneratedSourceContains(string source, IIncrementalGenerator[] generators, string filename, string[] snippets)
+    {
+        // Ensure CommunityToolkit.Mvvm and System.ComponentModel.DataAnnotations are loaded
+        Type observableObjectType = typeof(ObservableObject);
+        Type validationAttributeType = typeof(ValidationAttribute);
+
+        IEnumerable<MetadataReference> references =
+            from assembly in AppDomain.CurrentDomain.GetAssemblies()
+            where !assembly.IsDynamic
+            let reference = MetadataReference.CreateFromFile(assembly.Location)
+            select reference;
+
+        SyntaxTree syntaxTree = CSharpSyntaxTree.ParseText(source, CSharpParseOptions.Default.WithLanguageVersion(LanguageVersion.CSharp10));
+
+        CSharpCompilation compilation = CSharpCompilation.Create(
+            "original",
+            [syntaxTree],
+            references,
+            new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary));
+
+        GeneratorDriver driver = CSharpGeneratorDriver.Create(generators).WithUpdatedParseOptions((CSharpParseOptions)syntaxTree.Options);
+
+        _ = driver.RunGeneratorsAndUpdateCompilation(compilation, out Compilation outputCompilation, out ImmutableArray<Diagnostic> diagnostics);
+
+        CollectionAssert.AreEquivalent(Array.Empty<Diagnostic>(), diagnostics);
+
+        SyntaxTree generatedTree = outputCompilation.SyntaxTrees.Single(tree => Path.GetFileName(tree.FilePath) == filename);
+        string generatedText = generatedTree.ToString();
+
+        foreach (string snippet in snippets)
+        {
+            StringAssert.Contains(generatedText, snippet);
+        }
+
+        GC.KeepAlive(observableObjectType);
+        GC.KeepAlive(validationAttributeType);
+    }
 }