Introduce fields for commands to get rid of null warnings

src/MvvmGen.SourceGenerators.Tests/ViewModelGeneratorTests/CommandAttributeTests.cs

@@ -30,20 +30,16 @@ namespace MyCode
 {{
     partial class EmployeeViewModel : global::MvvmGen.ViewModels.ViewModelBase
     {{
+        private IDelegateCommand? _saveAllCommand;
+
         public EmployeeViewModel()
         {{
-            this.InitializeCommands();
             this.OnInitialize();
         }}
 
         partial void OnInitialize();
 
-        private void InitializeCommands()
-        {{
-            SaveAllCommand = new DelegateCommand(_ => SaveAll());
-        }}
-
-        public DelegateCommand SaveAllCommand {{ get; private set; }}
+        public IDelegateCommand SaveAllCommand => _saveAllCommand ??= new DelegateCommand(_ => SaveAll());
     }}
 }}
 ");
@@ -76,20 +72,16 @@ namespace MyCode
 {{
     partial class EmployeeViewModel : global::MvvmGen.ViewModels.ViewModelBase
     {{
+        private IDelegateCommand? _saveAllCommand;
+
         public EmployeeViewModel()
         {{
-            this.InitializeCommands();
             this.OnInitialize();
         }}
 
         partial void OnInitialize();
 
-        private void InitializeCommands()
-        {{
-            SaveAllCommand = new DelegateCommand(_ => SaveAll(), _ => CanSaveAll());
-        }}
-
-        public DelegateCommand SaveAllCommand {{ get; private set; }}
+        public IDelegateCommand SaveAllCommand => _saveAllCommand ??= new DelegateCommand(_ => SaveAll(), _ => CanSaveAll());
     }}
 }}
 ");
@@ -122,20 +114,16 @@ namespace MyCode
 {{
     partial class EmployeeViewModel : global::MvvmGen.ViewModels.ViewModelBase
     {{
+        private IDelegateCommand? _superCommand;
+
         public EmployeeViewModel()
         {{
-            this.InitializeCommands();
             this.OnInitialize();
         }}
 
         partial void OnInitialize();
 
-        private void InitializeCommands()
-        {{
-            SuperCommand = new DelegateCommand(_ => SaveAll(), _ => CanSaveAll());
-        }}
-
-        public DelegateCommand SuperCommand {{ get; private set; }}
+        public IDelegateCommand SuperCommand => _superCommand ??= new DelegateCommand(_ => SaveAll(), _ => CanSaveAll());
     }}
 }}
 ");
@@ -172,20 +160,16 @@ namespace MyCode
 {{
     partial class EmployeeViewModel : global::MvvmGen.ViewModels.ViewModelBase
     {{
+        private IDelegateCommand? _saveCommand;
+
         public EmployeeViewModel()
         {{
-            this.InitializeCommands();
             this.OnInitialize();
         }}
 
         partial void OnInitialize();
 
-        private void InitializeCommands()
-        {{
-            SaveCommand = new DelegateCommand({expectedConstructorArguments});
-        }}
-
-        public DelegateCommand SaveCommand {{ get; private set; }}
+        public IDelegateCommand SaveCommand => _saveCommand ??= new DelegateCommand({expectedConstructorArguments});
     }}
 }}
 ");

src/MvvmGen.SourceGenerators.Tests/ViewModelGeneratorTests/CommandInvalidateAttribute.cs

@@ -85,20 +85,16 @@ namespace MyCode
 {{
     partial class EmployeeViewModel : global::MvvmGen.ViewModels.ViewModelBase
     {{
+        private IDelegateCommand? _saveCommand;
+
         public EmployeeViewModel()
         {{
-            this.InitializeCommands();
             this.OnInitialize();
         }}
 
         partial void OnInitialize();
 
-        private void InitializeCommands()
-        {{
-            SaveCommand = new DelegateCommand(_ => Save(), _ => CanSave());
-        }}
-
-        public DelegateCommand SaveCommand {{ get; private set; }}
+        public IDelegateCommand SaveCommand => _saveCommand ??= new DelegateCommand(_ => Save(), _ => CanSave());
 
         public string FirstName
         {{
@@ -170,23 +166,19 @@ namespace MyCode
 {{
     partial class EmployeeViewModel : global::MvvmGen.ViewModels.ViewModelBase
     {{
+        private IDelegateCommand? _saveCommand;
+        private IDelegateCommand? _deleteCommand;
+
         public EmployeeViewModel()
         {{
-            this.InitializeCommands();
             this.OnInitialize();
         }}
 
         partial void OnInitialize();
 
-        private void InitializeCommands()
-        {{
-            SaveCommand = new DelegateCommand(_ => Save(), _ => CanSave());
-            DeleteCommand = new DelegateCommand(_ => Delete(), _ => CanDelete());
-        }}
-
-        public DelegateCommand SaveCommand {{ get; private set; }}
+        public IDelegateCommand SaveCommand => _saveCommand ??= new DelegateCommand(_ => Save(), _ => CanSave());
 
-        public DelegateCommand DeleteCommand {{ get; private set; }}
+        public IDelegateCommand DeleteCommand => _deleteCommand ??= new DelegateCommand(_ => Delete(), _ => CanDelete());
 
         public string FirstName
         {{
@@ -252,7 +244,7 @@ public partial class EmployeeViewModel
     [Command(nameof(CanSave))]
     public void Save() {{ }}
 
-    [CommandInvalidate(nameof(FirstName);
+    [CommandInvalidate(nameof(FirstName))]
     public bool CanSave() => true;
   }}
 }}",
@@ -262,20 +254,16 @@ namespace MyCode
 {{
     partial class EmployeeViewModel : global::MvvmGen.ViewModels.ViewModelBase
     {{
+        private IDelegateCommand? _saveCommand;
+
         public EmployeeViewModel()
         {{
-            this.InitializeCommands();
             this.OnInitialize();
         }}
 
         partial void OnInitialize();
 
-        private void InitializeCommands()
-        {{
-            SaveCommand = new DelegateCommand(_ => Save(), _ => CanSave());
-        }}
-
-        public DelegateCommand SaveCommand {{ get; private set; }}
+        public IDelegateCommand SaveCommand => _saveCommand ??= new DelegateCommand(_ => Save(), _ => CanSave());
 
         protected override void InvalidateCommands(string? propertyName)
         {{

src/MvvmGen.SourceGenerators.Tests/ViewModelGeneratorTests/ViewModelGenerateInterfaceAttributeTests.cs

@@ -165,25 +165,21 @@ namespace MyCode
 {{
     partial class EmployeeViewModel : global::MvvmGen.ViewModels.ViewModelBase, IEmployeeViewModel
     {{
+        private IDelegateCommand? _saveCommand;
+
         public EmployeeViewModel()
         {{
-            this.InitializeCommands();
             this.OnInitialize();
         }}
 
         partial void OnInitialize();
 
-        private void InitializeCommands()
-        {{
-            SaveCommand = new DelegateCommand(_ => Save());
-        }}
-
-        public DelegateCommand SaveCommand {{ get; private set; }}
+        public IDelegateCommand SaveCommand => _saveCommand ??= new DelegateCommand(_ => Save());
     }}
 
     public interface IEmployeeViewModel
     {{
-        DelegateCommand SaveCommand {{ get; }}
+        IDelegateCommand SaveCommand {{ get; }}
         void Save();
     }}
 }}

src/MvvmGen.SourceGenerators/Generators/CommandFieldGenerator.cs

@@ -0,0 +1,27 @@
+// ***********************************************************************
+// ⚡ MvvmGen => https://github.com/thomasclaudiushuber/mvvmgen
+// Copyright © by Thomas Claudius Huber
+// Licensed under the MIT license => See LICENSE file in repository root
+// ***********************************************************************
+
+using System.Collections.Generic;
+using System.Linq;
+using MvvmGen.Model;
+
+namespace MvvmGen.Generators
+{
+    internal static class CommandFieldGenerator
+    {
+        internal static void GenerateCommandFields(this ViewModelBuilder vmBuilder, IEnumerable<CommandToGenerate>? commandsToGenerate)
+        {
+            if (commandsToGenerate is not null && commandsToGenerate.Any())
+            {
+                vmBuilder.AppendLineBeforeMember();
+                foreach (var commandToGenerate in commandsToGenerate)
+                {
+                    vmBuilder.AppendLine($"private IDelegateCommand? {commandToGenerate.FieldName};");
+                }
+            }
+        }
+    }
+}

src/MvvmGen.SourceGenerators/Generators/CommandPropertyGenerator.cs

@@ -18,9 +18,26 @@ internal static void GenerateCommandProperties(this ViewModelBuilder vmBuilder,
                 foreach (var commandToGenerate in commandsToGenerate)
                 {
                     vmBuilder.AppendLineBeforeMember();
-                    vmBuilder.AppendLine($"public DelegateCommand {commandToGenerate.PropertyName} {{ get; private set; }}");
+                    vmBuilder.Append($"public IDelegateCommand {commandToGenerate.PropertyName} => {commandToGenerate.FieldName} ??= new DelegateCommand({GetMethodCall(commandToGenerate.ExecuteMethod)}");
+                    if (commandToGenerate.CanExecuteMethod is not null)
+                    {
+                        vmBuilder.Append($", {GetMethodCall(commandToGenerate.CanExecuteMethod)}");
+                    }
+
+                    vmBuilder.AppendLine(");");
                 }
             }
         }
+
+        private static object GetMethodCall(CommandMethod methodInfo)
+        {
+            return methodInfo switch
+            {
+                { IsAwaitable: true, HasParameter: true } => $"async x => await {methodInfo.Name}(x)",
+                { IsAwaitable: true, HasParameter: false } => $"async _ => await {methodInfo.Name}()",
+                { IsAwaitable: false, HasParameter: true } => $"{methodInfo.Name}",
+                { IsAwaitable: false, HasParameter: false } => $"_ => {methodInfo.Name}()",
+            };
+        }
     }
 }

src/MvvmGen.SourceGenerators/Generators/ConstructorGenerator.cs

@@ -19,14 +19,12 @@ internal static void GenerateConstructor(this ViewModelBuilder vmBuilder, ViewMo
             {
                 Generate(vmBuilder, viewModelToGenerate.ClassName,
                             viewModelToGenerate.InjectionsToGenerate,
-                            viewModelToGenerate.CommandsToGenerate?.Any() == true,
                             viewModelToGenerate.IsEventSubscriber);
             }
         }
 
         private static void Generate(ViewModelBuilder vmBuilder, string viewModelClassName,
-            IEnumerable<InjectionToGenerate>? injectionsToGenerate,
-            bool hasCommands, bool isEventSubscriber)
+            IEnumerable<InjectionToGenerate>? injectionsToGenerate, bool isEventSubscriber)
         {
             vmBuilder.AppendLineBeforeMember();
             vmBuilder.Append($"public {viewModelClassName}(");
@@ -72,18 +70,11 @@ private static void Generate(ViewModelBuilder vmBuilder, string viewModelClassNa
                 vmBuilder.AppendLine($"{eventAggregatorAccessForSubscription}.RegisterSubscriber(this);");
             }
 
-            if (hasCommands)
-            {
-                vmBuilder.AppendLine($"this.InitializeCommands();");
-            }
-
             vmBuilder.AppendLine($"this.OnInitialize();");
             vmBuilder.DecreaseIndent();
             vmBuilder.AppendLine("}");
             vmBuilder.AppendLine();
             vmBuilder.AppendLine($"partial void OnInitialize();");
-
-
         }
     }
 }

src/MvvmGen.SourceGenerators/Inspectors/ViewModelGenerateInterfaceAttributeInspector.cs

@@ -82,7 +82,7 @@ internal static class ViewModelGenerateInterfaceAttributeInspector
                 foreach (var commandToGenerate in commandsToGenerate)
                 {
                     properties ??= new();
-                    properties.Add(new InterfaceProperty(commandToGenerate.PropertyName, "DelegateCommand", true));
+                    properties.Add(new InterfaceProperty(commandToGenerate.PropertyName, "IDelegateCommand", true));
                 }
             }
 

src/MvvmGen.SourceGenerators/Model/CommandToGenerate.cs

@@ -15,12 +15,15 @@ public CommandToGenerate(CommandMethod executeMethod, string propertyName)
         {
             ExecuteMethod = executeMethod;
             PropertyName = propertyName;
+            FieldName = $"_{PropertyName.Substring(0,1).ToLower()}{PropertyName.Substring(1)}";
         }
 
         public CommandMethod ExecuteMethod { get; }
 
         public string PropertyName { get; }
 
+        public string FieldName { get; }
+
         public CommandMethod? CanExecuteMethod { get; set; }
 
         public override bool Equals(object? obj)

src/MvvmGen.SourceGenerators/MvvmGen.SourceGenerators.csproj

@@ -24,6 +24,7 @@
     <EmbeddedResource Include="..\MvvmGen\Attributes\ViewModelGenerateFactoryAttribute.cs" Link="MvvmGenLib\Attributes\ViewModelGenerateFactoryAttribute.cs" />
     <EmbeddedResource Include="..\MvvmGen\Attributes\ViewModelGenerateInterfaceAttribute.cs" Link="MvvmGenLib\Attributes\ViewModelGenerateInterfaceAttribute.cs" />
     <EmbeddedResource Include="..\MvvmGen\Commands\DelegateCommand.cs" Link="MvvmGenLib\Commands\DelegateCommand.cs" />
+    <EmbeddedResource Include="..\MvvmGen\Commands\IDelegateCommand.cs" Link="MvvmGenLib\Commands\IDelegateCommand.cs" />
     <EmbeddedResource Include="..\MvvmGen\Events\EventAggregator.cs" Link="MvvmGenLib\Events\EventAggregator.cs" />
     <EmbeddedResource Include="..\MvvmGen\Events\IEventAggregator.cs" Link="MvvmGenLib\Events\IEventAggregator.cs" />
     <EmbeddedResource Include="..\MvvmGen\Events\IEventSubscriber.cs" Link="MvvmGenLib\Events\IEventSubscriber.cs" />

src/MvvmGen.SourceGenerators/ViewModelGenerator.cs

@@ -21,7 +21,7 @@
     /// Generates ViewModels for classes that are decorated with the MvvmGen.ViewModelAttribute.
     /// </summary>
     [Generator]
     public class ViewModelGenerator : IIncrementalGenerator
     {
         private static readonly string _versionString;
 
@@ -137,9 +137,9 @@
 
             vmBuilder.GenerateClass(viewModelToGenerate);
 
-            vmBuilder.GenerateConstructor(viewModelToGenerate);
+            vmBuilder.GenerateCommandFields(viewModelToGenerate.CommandsToGenerate);
 
-            vmBuilder.GenerateCommandInitializeMethod(viewModelToGenerate.CommandsToGenerate);
+            vmBuilder.GenerateConstructor(viewModelToGenerate);
 
             vmBuilder.GenerateCommandProperties(viewModelToGenerate.CommandsToGenerate);