fix: relayCommand when canExecute is a property

Author: davidkallesen

src/Atc.Wpf.SourceGenerators/Extensions/ViewModelBuilderExtensions.cs

@@ -82,7 +82,8 @@ private static void GenerateRelayCommandWithOutParameterValues(
                 implementationType,
                 rc.CommandName,
                 rc.MethodName,
-                rc.CanExecuteName);
+                rc.CanExecuteName,
+                rc.UsePropertyForCanExecute);
             builder.AppendLine(cmd);
         }
         else if (rc.ParameterTypes.Length == 1)
@@ -108,7 +109,8 @@ private static void GenerateRelayCommandWithOutParameterValues(
                     $"{implementationType}{generic}",
                     rc.CommandName,
                     rc.MethodName,
-                    rc.CanExecuteName);
+                    rc.CanExecuteName,
+                    rc.UsePropertyForCanExecute);
                 builder.AppendLine(cmd);
             }
         }
@@ -229,14 +231,29 @@ private static string GenerateCommandLine(
         string commandName,
         string constructorParameters,
         string? canExecuteName = null,
+        bool usePropertyForCanExecute = false,
         bool isLambda = false)
     {
         var lambdaPrefix = isLambda ? "() => " : string.Empty;
         var commandInstance = $"new {implementationType}({lambdaPrefix}{constructorParameters}";
 
         if (canExecuteName is not null)
         {
-            commandInstance += $", {canExecuteName}";
+            if (usePropertyForCanExecute)
+            {
+                if (interfaceType.Contains('<'))
+                {
+                    commandInstance += $", _ => {canExecuteName}";
+                }
+                else
+                {
+                    commandInstance += $", () => {canExecuteName}";
+                }
+            }
+            else
+            {
+                commandInstance += $", {canExecuteName}";
+            }
         }
 
         commandInstance += ");";

test/Atc.Wpf.SourceGenerators.Tests/Generators/ViewModelGeneratorTests.cs

@@ -1004,6 +1004,84 @@ public partial class TestViewModel
         AssertGeneratorRunResultAsEqual(expectedCode, generatorResult);
     }
 
+    [Fact]
+    public void RelayCommand_NoParameter_CanExecuteOnProperty()
+    {
+        const string inputCode =
+            """
+            namespace TestNamespace;
+
+            public partial class TestViewModel : ViewModelBase
+            {
+                [RelayCommand(CanExecute = nameof(CanSave))]
+                public void Save()
+                {
+                }
+                
+                public bool CanSave => return true;
+            }
+            """;
+
+        const string expectedCode =
+            """
+            // <auto-generated>
+            #nullable enable
+            using Atc.Wpf.Command;
+
+            namespace TestNamespace;
+
+            public partial class TestViewModel
+            {
+                public IRelayCommand SaveCommand => new RelayCommand(Save, () => CanSave);
+            }
+
+            #nullable disable
+            """;
+
+        var generatorResult = RunGenerator<ViewModelGenerator>(inputCode);
+
+        AssertGeneratorRunResultAsEqual(expectedCode, generatorResult);
+    }
+
+    [Fact]
+    public void RelayCommand_ParameterString_CanExecuteOnProperty()
+    {
+        const string inputCode =
+            """
+            namespace TestNamespace;
+
+            public partial class TestViewModel : ViewModelBase
+            {
+                [RelayCommand(CanExecute = nameof(CanSave))]
+                public void Save(string val)
+                {
+                }
+                
+                public bool CanSave => return true;
+            }
+            """;
+
+        const string expectedCode =
+            """
+            // <auto-generated>
+            #nullable enable
+            using Atc.Wpf.Command;
+
+            namespace TestNamespace;
+
+            public partial class TestViewModel
+            {
+                public IRelayCommand<string> SaveCommand => new RelayCommand<string>(Save, _ => CanSave);
+            }
+
+            #nullable disable
+            """;
+
+        var generatorResult = RunGenerator<ViewModelGenerator>(inputCode);
+
+        AssertGeneratorRunResultAsEqual(expectedCode, generatorResult);
+    }
+
     [Fact]
     public void AsyncRelayCommand_NoParameter()
     {