Enabled nullability annotations for [ObservableProperty]

Author: Sergio0694

Microsoft.Toolkit.Mvvm.SourceGenerators/ComponentModel/ObservablePropertyGenerator.cs

@@ -339,6 +339,14 @@ private static PropertyDeclarationSyntax CreatePropertyDeclaration(
                         updateAndNotificationBlock));
             }
 
+            // Get the right type for the declared property (including nullability annotations)
+            TypeSyntax propertyType = IdentifierName(typeName);
+
+            if (fieldSymbol.Type is { IsReferenceType: true, NullableAnnotation: NullableAnnotation.Annotated })
+            {
+                propertyType = NullableType(propertyType);
+            }
+
             // Construct the generated property as follows:
             //
             // <FIELD_TRIVIA>
@@ -349,7 +357,7 @@ private static PropertyDeclarationSyntax CreatePropertyDeclaration(
             // <VALIDATION_ATTRIBUTE2>
             // ...
             // <VALIDATION_ATTRIBUTEN>
-            // public <FIELD_TYPE> <PROPERTY_NAME>
+            // public <FIELD_TYPE><NULLABLE_ANNOTATION?> <PROPERTY_NAME>
             // {
             //     get => <FIELD_NAME>;
             //     set
@@ -358,7 +366,7 @@ private static PropertyDeclarationSyntax CreatePropertyDeclaration(
             //     }
             // }
             return
-                PropertyDeclaration(IdentifierName(typeName), Identifier(propertyName))
+                PropertyDeclaration(propertyType, Identifier(propertyName))
                 .AddAttributeLists(
                     AttributeList(SingletonSeparatedList(
                         Attribute(IdentifierName("global::System.CodeDom.Compiler.GeneratedCode"))

UnitTests/UnitTests.NetCore/Mvvm/Test_ObservablePropertyAttribute.cs

@@ -10,6 +10,8 @@
 using Microsoft.Toolkit.Mvvm.ComponentModel;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
+#nullable enable
+
 namespace UnitTests.Mvvm
 {
     [TestClass]
@@ -128,11 +130,11 @@ public sealed partial class DependentPropertyModel
         {
             [ObservableProperty]
             [AlsoNotifyFor(nameof(FullName))]
-            private string name;
+            private string? name;
 
             [ObservableProperty]
             [AlsoNotifyFor(nameof(FullName))]
-            private string surname;
+            private string? surname;
 
             public string FullName => $"{Name} {Surname}";
         }
@@ -143,15 +145,15 @@ public partial class MyFormViewModel : ObservableValidator
             [Required]
             [MinLength(1)]
             [MaxLength(100)]
-            private string name;
+            private string? name;
 
             [ObservableProperty]
             [Range(0, 120)]
             private int age;
 
             [ObservableProperty]
             [EmailAddress]
-            private string email;
+            private string? email;
 
             [ObservableProperty]
             [TestValidation(null, typeof(SampleModel), true, 6.28, new[] { "Bob", "Ross" }, NestedArray = new object[] { 1, "Hello", new int[] { 2, 3, 4 } }, Animal = Animal.Llama)]
@@ -160,7 +162,7 @@ public partial class MyFormViewModel : ObservableValidator
 
         private sealed class TestValidationAttribute : ValidationAttribute
         {
-            public TestValidationAttribute(object o, Type t, bool flag, double d, string[] names)
+            public TestValidationAttribute(object? o, Type t, bool flag, double d, string[] names)
             {
                 O = o;
                 T = t;
@@ -169,7 +171,7 @@ public TestValidationAttribute(object o, Type t, bool flag, double d, string[] n
                 Names = names;
             }
 
-            public object O { get; }
+            public object? O { get; }
 
             public Type T { get; }