Fix diagnostics for generated properties

Author: Sergio0694

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

@@ -138,12 +138,34 @@ private static bool TryGatherDependentPropertyChangedNames(
                     }
                     else
                     {
-                        diagnostics.Add(
-                            AlsoNotifyChangeForInvalidTargetError,
-                            fieldSymbol,
-                            dependentPropertyName ?? "",
-                            fieldSymbol.ContainingType);
-                    }                    
+                        bool isTargetValid = false;
+
+                        // Check for generated properties too
+                        foreach (ISymbol member in fieldSymbol.ContainingType.GetMembers())
+                        {
+                            if (member is IFieldSymbol otherFieldSymbol &&
+                                !SymbolEqualityComparer.Default.Equals(fieldSymbol, otherFieldSymbol) &&
+                                otherFieldSymbol.HasAttributeWithFullyQualifiedName("global::CommunityToolkit.Mvvm.ComponentModel.ObservablePropertyAttribute") &&
+                                dependentPropertyName == GetGeneratedPropertyName(otherFieldSymbol))
+                            {
+                                propertyChangedNames.Add(dependentPropertyName);
+
+                                isTargetValid = true;
+
+                                break;
+                            }
+                        }
+
+                        // Add the diagnostic if the target is definitely invalid
+                        if (!isTargetValid)
+                        {
+                            diagnostics.Add(
+                                AlsoNotifyChangeForInvalidTargetError,
+                                fieldSymbol,
+                                dependentPropertyName ?? "",
+                                fieldSymbol.ContainingType);
+                        }
+                    }
                 }
 
                 return true;

CommunityToolkit.Mvvm.SourceGenerators/Extensions/ISymbolExtensions.cs

@@ -2,6 +2,7 @@
 // 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.Collections.Immutable;
 using Microsoft.CodeAnalysis;
 
 namespace CommunityToolkit.Mvvm.SourceGenerators.Extensions;
@@ -32,6 +33,27 @@ public static bool HasFullyQualifiedName(this ISymbol symbol, string name)
         return symbol.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat) == name;
     }
 
+    /// <summary>
+    /// Checks whether or not a given symbol has an attribute with the specified full name.
+    /// </summary>
+    /// <param name="symbol">The input <see cref="ISymbol"/> instance to check.</param>
+    /// <param name="name">The attribute name to look for.</param>
+    /// <returns>Whether or not <paramref name="symbol"/> has an attribute with the specified name.</returns>
+    public static bool HasAttributeWithFullyQualifiedName(this ISymbol symbol, string name)
+    {
+        ImmutableArray<AttributeData> attributes = symbol.GetAttributes();
+
+        foreach (AttributeData attribute in attributes)
+        {
+            if (attribute.AttributeClass?.HasFullyQualifiedName(name) == true)
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     /// <summary>
     /// Calculates the effective accessibility for a given symbol.
     /// </summary>