Add diagnostics for invalid target of [AlsoNotifyChangeFor]

Author: Sergio0694

CommunityToolkit.Mvvm.SourceGenerators/AnalyzerReleases.Unshipped.md

@@ -19,3 +19,4 @@ MVVMTK0011 | CommunityToolkit.Mvvm.SourceGenerators.ICommandGenerator | Error |
 MVVMTK0012 | CommunityToolkit.Mvvm.SourceGenerators.ICommandGenerator | Error | See https://aka.ms/mvvmtoolkit/error
 MVVMTK0013 | CommunityToolkit.Mvvm.SourceGenerators.ICommandGenerator | Error | See https://aka.ms/mvvmtoolkit/error
 MVVMTK0014 | CommunityToolkit.Mvvm.SourceGenerators.ICommandGenerator | Error | See https://aka.ms/mvvmtoolkit/error
+MVVMTK0015 | CommunityToolkit.Mvvm.SourceGenerators.ICommandGenerator | Error | See https://aka.ms/mvvmtoolkit/error

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

@@ -73,13 +73,8 @@ public static PropertyInfo GetInfo(IFieldSymbol fieldSymbol, out ImmutableArray<
             // Gather attributes info
             foreach (AttributeData attributeData in fieldSymbol.GetAttributes())
             {
-                // Add dependent property notifications, if needed
-                if (attributeData.AttributeClass?.HasFullyQualifiedName("global::CommunityToolkit.Mvvm.ComponentModel.AlsoNotifyChangeForAttribute") == true)
+                if (TryGatherDependentPropertyChangedNames(fieldSymbol, attributeData, propertyChangedNames, builder))
                 {
-                    foreach (string dependentPropertyName in attributeData.GetConstructorArguments<string>())
-                    {
-                        propertyChangedNames.Add(dependentPropertyName);
-                    }
                 }
                 else if (attributeData.AttributeClass?.HasFullyQualifiedName("global::CommunityToolkit.Mvvm.ComponentModel.AlsoNotifyCanExecuteForAttribute") == true)
                 {
@@ -121,6 +116,46 @@ public static PropertyInfo GetInfo(IFieldSymbol fieldSymbol, out ImmutableArray<
                 validationAttributes.ToImmutable());
         }
 
+        /// <summary>
+        /// Tries to gather dependent properties from the given attribute.
+        /// </summary>
+        /// <param name="fieldSymbol">The input <see cref="IFieldSymbol"/> instance to process.</param>
+        /// <param name="attributeData">The <see cref="AttributeData"/> instance for <paramref name="fieldSymbol"/>.</param>
+        /// <param name="propertyChangedNames">The target collection of dependent property names to populate.</param>
+        /// <param name="diagnostics">The current collection of gathered diagnostics.</param>
+        /// <returns>Whether or not <paramref name="attributeData"/> was an attribute containing any dependent properties.</returns>
+        private static bool TryGatherDependentPropertyChangedNames(
+            IFieldSymbol fieldSymbol,
+            AttributeData attributeData,
+            ImmutableArray<string>.Builder propertyChangedNames,
+            ImmutableArray<Diagnostic>.Builder diagnostics)
+        {
+            if (attributeData.AttributeClass?.HasFullyQualifiedName("global::CommunityToolkit.Mvvm.ComponentModel.AlsoNotifyChangeForAttribute") == true)
+            {
+                foreach (string? dependentPropertyName in attributeData.GetConstructorArguments<string>())
+                {
+                    // Each target must be a string matching the name of a property from the containing type of the annotated field
+                    if (dependentPropertyName is { Length: > 0 } &&
+                        fieldSymbol.ContainingType.GetMembers(dependentPropertyName).OfType<IPropertySymbol>().Any())
+                    {
+                        propertyChangedNames.Add(dependentPropertyName);
+                    }
+                    else
+                    {
+                        diagnostics.Add(
+                            AlsoNotifyChangeForInvalidTargetError,
+                            fieldSymbol,
+                            dependentPropertyName ?? "",
+                            fieldSymbol.ContainingType);
+                    }                    
+                }
+
+                return true;
+            }
+
+            return false;
+        }
+
         /// <summary>
         /// Gets a <see cref="CompilationUnitSyntax"/> instance with the cached args for property changing notifications.
         /// </summary>

CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/DiagnosticDescriptors.cs

@@ -235,4 +235,20 @@ internal static class DiagnosticDescriptors
         isEnabledByDefault: true,
         description: $"The name of fields annotated with [ObservableProperty] should use \"lowerCamel\", \"_lowerCamel\" or \"m_lowerCamel\" pattern to avoid collisions with the generated properties.",
         helpLinkUri: "https://aka.ms/mvvmtoolkit");
+
+    /// <summary>
+    /// Gets a <see cref="DiagnosticDescriptor"/> indicating when the specified target for <c>[AlsoNotifyChangeFor]</c> is not valid.
+    /// <para>
+    /// Format: <c>"The target(s) of [AlsoNotifyChangeFor] must be an accessible property, but "{0}" has no matches in type {1}</c>.
+    /// </para>
+    /// </summary>
+    public static readonly DiagnosticDescriptor AlsoNotifyChangeForInvalidTargetError = new DiagnosticDescriptor(
+        id: "MVVMTK0015",
+        title: "Name collision for generated property",
+        messageFormat: "The target(s) of [AlsoNotifyChangeFor] must be an accessible property, but \"{0}\" has no matches in type {1}",
+        category: typeof(ObservablePropertyGenerator).FullName,
+        defaultSeverity: DiagnosticSeverity.Error,
+        isEnabledByDefault: true,
+        description: "The target(s) of [AlsoNotifyChangeFor] must be an accessible property in its parent type.",
+        helpLinkUri: "https://aka.ms/mvvmtoolkit");
 }

CommunityToolkit.Mvvm.SourceGenerators/Extensions/AttributeDataExtensions.cs

@@ -87,15 +87,16 @@ public static bool TryGetNamedArgument<T>(this AttributeData attributeData, stri
     /// <typeparam name="T">The type of constructor arguments to retrieve.</typeparam>
     /// <param name="attributeData">The target <see cref="AttributeData"/> instance to get the arguments from.</param>
     /// <returns>A sequence of all constructor arguments of the specified type from <paramref name="attributeData"/>.</returns>
-    public static IEnumerable<T> GetConstructorArguments<T>(this AttributeData attributeData)
+    public static IEnumerable<T?> GetConstructorArguments<T>(this AttributeData attributeData)
+        where T : class
     {
-        static IEnumerable<T> Enumerate(IEnumerable<TypedConstant> constants)
+        static IEnumerable<T?> Enumerate(IEnumerable<TypedConstant> constants)
         {
             foreach (TypedConstant constant in constants)
             {
                 if (constant.IsNull)
                 {
-                    continue;
+                    yield return null;
                 }
 
                 if (constant.Kind == TypedConstantKind.Primitive &&
@@ -105,7 +106,7 @@ static IEnumerable<T> Enumerate(IEnumerable<TypedConstant> constants)
                 }
                 else if (constant.Kind == TypedConstantKind.Array)
                 {
-                    foreach (T item in Enumerate(constant.Values))
+                    foreach (T? item in Enumerate(constant.Values))
                     {
                         yield return item;
                     }