Properly forward nullability annotations for [ICommand]

Author: Sergio0694

CommunityToolkit.Mvvm.SourceGenerators/Input/ICommandGenerator.Execute.cs

@@ -419,8 +419,8 @@ private static bool TryMapCommandTypesFromMethod(
                 commandClassType = "global::CommunityToolkit.Mvvm.Input.RelayCommand";
                 delegateType = "global::System.Action";
                 supportsCancellation = false;
-                commandTypeArguments = ImmutableArray.Create(parameter.Type.GetFullyQualifiedName());
-                delegateTypeArguments = ImmutableArray.Create(parameter.Type.GetFullyQualifiedName());
+                commandTypeArguments = ImmutableArray.Create(parameter.Type.GetFullyQualifiedNameWithNullabilityAnnotations());
+                delegateTypeArguments = ImmutableArray.Create(parameter.Type.GetFullyQualifiedNameWithNullabilityAnnotations());
 
                 return true;
             }
@@ -453,7 +453,7 @@ private static bool TryMapCommandTypesFromMethod(
                         delegateType = "global::System.Func";
                         supportsCancellation = true;
                         commandTypeArguments = ImmutableArray<string>.Empty;
-                        delegateTypeArguments = ImmutableArray.Create(singleParameter.Type.GetFullyQualifiedName(), "global::System.Threading.Tasks.Task");
+                        delegateTypeArguments = ImmutableArray.Create("global::System.Threading.CancellationToken", "global::System.Threading.Tasks.Task");
 
                         return true;
                     }
@@ -463,8 +463,8 @@ private static bool TryMapCommandTypesFromMethod(
                     commandClassType = "global::CommunityToolkit.Mvvm.Input.AsyncRelayCommand";
                     delegateType = "global::System.Func";
                     supportsCancellation = false;
-                    commandTypeArguments = ImmutableArray.Create(singleParameter.Type.GetFullyQualifiedName());
-                    delegateTypeArguments = ImmutableArray.Create(singleParameter.Type.GetFullyQualifiedName(), "global::System.Threading.Tasks.Task");
+                    commandTypeArguments = ImmutableArray.Create(singleParameter.Type.GetFullyQualifiedNameWithNullabilityAnnotations());
+                    delegateTypeArguments = ImmutableArray.Create(singleParameter.Type.GetFullyQualifiedNameWithNullabilityAnnotations(), "global::System.Threading.Tasks.Task");
 
                     return true;
                 }
@@ -479,8 +479,8 @@ private static bool TryMapCommandTypesFromMethod(
                     commandClassType = "global::CommunityToolkit.Mvvm.Input.AsyncRelayCommand";
                     delegateType = "global::System.Func";
                     supportsCancellation = true;
-                    commandTypeArguments = ImmutableArray.Create(firstParameter.Type.GetFullyQualifiedName());
-                    delegateTypeArguments = ImmutableArray.Create(firstParameter.Type.GetFullyQualifiedName(), secondParameter.Type.GetFullyQualifiedName(), "global::System.Threading.Tasks.Task");
+                    commandTypeArguments = ImmutableArray.Create(firstParameter.Type.GetFullyQualifiedNameWithNullabilityAnnotations());
+                    delegateTypeArguments = ImmutableArray.Create(firstParameter.Type.GetFullyQualifiedNameWithNullabilityAnnotations(), "global::System.Threading.CancellationToken", "global::System.Threading.Tasks.Task");
 
                     return true;
                 }

tests/CommunityToolkit.Mvvm.UnitTests/Test_ICommandAttribute.cs

@@ -500,6 +500,23 @@ public async Task Test_ICommandAttribute_WithOnPrefixes()
         Assert.IsTrue(model.HasDownloadCommandRun);
     }
 
+    // See https://github.com/CommunityToolkit/dotnet/issues/283
+    [TestMethod]
+    public void Test_ICommandAttribute_VerifyNoWarningsForNullableValues()
+    {
+        ModelWithCommandsWithNullabilityAnnotations model = new();
+
+        // Here we just need to verify we don't get any warnings.
+        // That is, that means the generated code has the right nullability annotations.
+        model.NullableObjectCommand.Execute(null);
+        model.ListWithNullableTypeCommand.Execute(null);
+        model.ListWithNullableTypeCommand.Execute(new List<object?>());
+        model.TupleWithNullableElementsCommand.Execute((DateTime.Now, null, null, null));
+        model.TupleWithNullableElementsCommand.Execute((DateTime.Now, null, true, new List<string>()));
+        model.TupleWithNullableElementsCommand.Execute((null, "Hello", null, null));
+        model.TupleWithNullableElementsCommand.Execute((null, null, null, null));
+    }
+
     #region Region
     public class Region
     {
@@ -871,4 +888,22 @@ private async Task OnDownloadAsync()
             HasDownloadCommandRun = true;
         }
     }
+
+    partial class ModelWithCommandsWithNullabilityAnnotations
+    {
+        [ICommand]
+        private void NullableObject(object? parameter)
+        {
+        }
+
+        [ICommand]
+        private void ListWithNullableType(List<object?> parameter)
+        {
+        }
+
+        [ICommand]
+        private void TupleWithNullableElements((DateTime? date, string? message, bool? shouldPrint, List<string>? stringList) parameter)
+        {
+        }
+    }
 }