WIP

MvvmEssentials.sln

@@ -10,6 +10,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Nkraft.CrossUtility", "..\C
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Nkraft.MvvmEssentials.UnitTest", "Tests\Nkraft.MvvmEssentials.UnitTest.csproj", "{E4346076-4B31-4966-BDF1-7653B584296F}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "FoodDelivery", "..\FoodDelivery\FoodDelivery\FoodDelivery.csproj", "{73066B82-45E7-4AD0-AD36-852A369F6E77}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -32,6 +34,10 @@ Global
 		{E4346076-4B31-4966-BDF1-7653B584296F}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{E4346076-4B31-4966-BDF1-7653B584296F}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{E4346076-4B31-4966-BDF1-7653B584296F}.Release|Any CPU.Build.0 = Release|Any CPU
+		{73066B82-45E7-4AD0-AD36-852A369F6E77}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{73066B82-45E7-4AD0-AD36-852A369F6E77}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{73066B82-45E7-4AD0-AD36-852A369F6E77}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{73066B82-45E7-4AD0-AD36-852A369F6E77}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

src/Attributes/ParameterAttribute.cs

@@ -0,0 +1,9 @@
+namespace Nkraft.MvvmEssentials.Attributes;
+
+[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
+public class ParameterAttribute : Attribute
+{
+    public bool IsRequired { get; set; }
+
+    public string? PreferredPropertyName { get; set; }
+}

Source/Extensions/NavigationServiceExtension.cs → src/Extensions/NavigationServiceExtension.cs

@@ -8,10 +8,24 @@
 // ReSharper disable once CheckNamespace
 namespace Nkraft.MvvmEssentials;
 
+public interface INavigationTarget;
+
 public static class NavigationExtension
 {
 	extension(INavigationService navigationService)
 	{
+		public async Task<IResult> NavigateAsync<TViewModel>(
+			INavigationTarget parameters, bool animated = true)
+			where TViewModel : PageViewModel
+		{
+			var pageName = PageHelper.ToPageName<TViewModel>("Page");
+			var navParam = new NavigationParameters();
+			foreach (var (key, value) in ObjectHelper.ToDictionary(parameters))
+				navParam.Add(key, value);
+			return await navigationService.NavigateAsync(pageName, navParam, animated);
+		}
+
+
 		/// <summary>
 		/// Navigates to the page associated with the specified ViewModel type, passing parameters as a strongly-typed object.
 		/// </summary>

Source/IsExternalInit.cs → src/IsExternalInit.cs

@@ -1,4 +1,4 @@
-// IsExternalInit.cs
+// ReSharper disable once CheckNamespace
 namespace System.Runtime.CompilerServices;
 
 internal static class IsExternalInit { }

Source/Nkraft.MvvmEssentials.csproj → src/Nkraft.MvvmEssentials.csproj

@@ -73,8 +73,14 @@
   <ItemGroup>
     <ProjectReference Include="..\..\CrossUtility\src\Nkraft.CrossUtility.csproj" />
     <ProjectReference Include="SourceGenerator\Nkraft.MvvmEssentials.SourceGenerator.csproj"
+                      OutputItemType="Analyzer"
                       ReferenceOutputAssembly="false"
-                      PrivateAssets="all" />
+                      PrivateAssets="all"
+                      Condition="'$(Configuration)' == 'Debug'" />
+    <ProjectReference Include="SourceGenerator\Nkraft.MvvmEssentials.SourceGenerator.csproj"
+                      ReferenceOutputAssembly="false"
+                      PrivateAssets="all"
+                      Condition="'$(Configuration)' != 'Debug'" />
   </ItemGroup>
 
 </Project>

src/SourceGenerator/IsExternalInit.cs

@@ -0,0 +1,7 @@
+using System.ComponentModel;
+
+// ReSharper disable once CheckNamespace
+namespace System.Runtime.CompilerServices;
+
+[EditorBrowsable(EditorBrowsableState.Never)]
+internal static class IsExternalInit { }

src/SourceGenerator/NavigationParametersGenerator.cs

@@ -0,0 +1,152 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+
+namespace Nkraft.MvvmEssentials.SourceGenerator;
+
+// per-property (your type, now a record so it has value equality for the incremental cache)
+public sealed record ViewModelParameters(string PropertyName, string PropertyType, bool IsRequired);
+
+// per-VM — this is what was missing: carries where to emit
+internal sealed record ViewModelTarget(string Namespace, string ClassName, EquatableArray<ViewModelParameters> Parameters);
+
+[Generator]
+public class NavigationParametersGenerator : IIncrementalGenerator
+{
+    private const string NavigableViewModelName  = "Nkraft.MvvmEssentials.ViewModels.NavigableEntryViewModel";
+    private const string NavigationParameterName = "Nkraft.MvvmEssentials.Attributes.ParameterAttribute";
+
+    void IIncrementalGenerator.Initialize(IncrementalGeneratorInitializationContext context)
+    {
+        var targets = context.SyntaxProvider.CreateSyntaxProvider(
+                predicate: static (node, _) => ClassPropertiesHasAttributes(node),
+                transform: static (ctx, _) => ToViewModelTarget(ctx))
+            .Where(static t => t is not null)
+            .Select(static (t, _) => t!);
+
+        context.RegisterSourceOutput(targets, static (spc, t) => Emit(spc, t));
+    }
+
+    private static bool ClassPropertiesHasAttributes(SyntaxNode node) =>
+        node is ClassDeclarationSyntax cls &&
+        cls.Members.OfType<PropertyDeclarationSyntax>().Any(p => p.AttributeLists.Count > 0);
+
+    private static ViewModelTarget? ToViewModelTarget(GeneratorSyntaxContext ctx)
+    {
+        var classDecl = (ClassDeclarationSyntax)ctx.Node;
+        if (ctx.SemanticModel.GetDeclaredSymbol(classDecl) is not INamedTypeSymbol symbol)
+            return null;
+        if (IsDerivedFrom(symbol, NavigableViewModelName) == false)
+            return null;
+
+        var props = symbol.GetMembers()
+            .OfType<IPropertySymbol>()
+            .Where(p => p.GetAttributes().Any(a => a.AttributeClass?.ToDisplayString() == NavigationParameterName))
+            .Select(p =>
+            {
+                var attr = p.GetAttributes().First(a => a.AttributeClass?.ToDisplayString() == NavigationParameterName);
+                // absent → required by default; opt out with [Parameter(IsRequired = false)]
+                var isRequired = attr.NamedArguments.FirstOrDefault(na => na.Key == "IsRequired").Value.Value as bool? ?? true;
+                return new ViewModelParameters(
+                    p.Name,
+                    p.Type.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat), // global:: → no resolution surprises
+                    isRequired);
+            })
+            .ToArray();
+
+        if (props.Length == 0)
+            return null;
+
+        var ns = symbol.ContainingNamespace.IsGlobalNamespace
+            ? string.Empty
+            : symbol.ContainingNamespace.ToDisplayString();
+
+        return new ViewModelTarget(ns, symbol.Name, new EquatableArray<ViewModelParameters>(props));
+    }
+
+    private static void Emit(SourceProductionContext spc, ViewModelTarget t)
+    {
+        var sb = new StringBuilder();
+        sb.AppendLine("// <auto-generated/>");
+        sb.AppendLine("#nullable enable");
+        if (t.Namespace.Length > 0)
+            sb.Append("namespace ").Append(t.Namespace).AppendLine(";").AppendLine();
+
+        sb.Append("partial class ").AppendLine(t.ClassName);
+        sb.AppendLine("{");
+
+        sb.Append("    public sealed record Parameters : global::Nkraft.MvvmEssentials.INavigationTarget<")
+          .Append(t.ClassName).AppendLine(">");
+        sb.AppendLine("    {");
+        foreach (var p in t.Parameters.Array)
+        {
+            sb.Append("        public ");
+            if (p.IsRequired) sb.Append("required ");
+            sb.Append(p.PropertyType).Append(' ').Append(p.PropertyName).AppendLine(" { get; init; }");
+        }
+        sb.AppendLine();
+        sb.AppendLine("        public global::Nkraft.MvvmEssentials.Services.INavigationParameters ToNavigationParameters()");
+        sb.AppendLine("        {");
+        sb.AppendLine("            var __p = new global::Nkraft.MvvmEssentials.Services.NavigationParameters();");
+        foreach (var p in t.Parameters.Array)
+            sb.Append("            __p.Add(\"").Append(p.PropertyName).Append("\", ").Append(p.PropertyName).AppendLine(");");
+        sb.AppendLine("            return __p;");
+        sb.AppendLine("        }");
+        sb.AppendLine("    }");
+        sb.AppendLine();
+
+        sb.AppendLine("    protected internal override void ApplyNavigationParameters(global::Nkraft.MvvmEssentials.Services.INavigationParameters parameters)");
+        sb.AppendLine("    {");
+        var i = 0;
+        foreach (var p in t.Parameters.Array)
+        {
+            var v = "__v" + i++;
+            sb.Append("        if (parameters.TryGetValue<").Append(p.PropertyType).Append(">(\"")
+              .Append(p.PropertyName).Append("\", out var ").Append(v).Append(")) this.")
+              .Append(p.PropertyName).Append(" = ").Append(v).AppendLine("!;");
+        }
+        sb.AppendLine("    }");
+
+        sb.AppendLine("}");
+
+        var hint = (t.Namespace.Length > 0 ? t.Namespace + "." : string.Empty) + t.ClassName + ".NavigationParameters.g.cs";
+        spc.AddSource(hint, sb.ToString());
+    }
+
+    private static bool IsDerivedFrom(INamedTypeSymbol symbol, string baseTypeName)
+    {
+        for (var t = symbol; t is not null; t = t.BaseType)
+            if (t.ToDisplayString() == baseTypeName)
+                return true;
+        return false;
+    }
+}
+
+// arrays don't have structural equality, which silently breaks incremental caching.
+// this wrapper restores it so the pipeline actually memoizes per-VM.
+internal readonly struct EquatableArray<T>(T[] array) : IEquatable<EquatableArray<T>> where T : IEquatable<T>
+{
+    public readonly T[] Array = array;
+
+    public bool Equals(EquatableArray<T> other)
+    {
+        if (Array is null) return false;
+        if (Array.Length != other.Array.Length) return false;
+        return Array.Where((t, i) => !t.Equals(other.Array[i])).Any() == false;
+    }
+
+    public override bool Equals(object? obj) => obj is EquatableArray<T> o && Equals(o);
+
+    public override int GetHashCode()
+    {
+        if (Array is null) return 0;
+        unchecked
+        {
+            return Array.Aggregate(17, (current, item) => current * 31 + item.GetHashCode());
+        }
+    }
+}

Source/ViewModels/NavigableEntryViewModel.cs → src/ViewModels/NavigableEntryViewModel.cs

@@ -1,4 +1,6 @@
 using System.Reflection;
+using Nkraft.CrossUtility.Helpers;
+using Nkraft.MvvmEssentials.Attributes;
 using Nkraft.MvvmEssentials.Services;
 using Nkraft.MvvmEssentials.Services.Navigation;
 using Nkraft.MvvmEssentials.Services.Pages;
@@ -12,9 +14,10 @@ public abstract class NavigableEntryViewModel : BaseViewModel,
 {
 	internal void SetNavigationParameter(string key, object? value)
 	{
-		var bindingFlags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;
+		const BindingFlags bindingFlags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic;
 		var property = GetType().GetProperty(key, bindingFlags);
-		if (property is null || property.CanWrite == false)
+		var hasParameterAttribute = property?.GetCustomAttributes<ParameterAttribute>().Any();
+		if (hasParameterAttribute == false || property is null || property.CanWrite == false)
 			return;
 
 		if (value is null || AreTypesEqual(property.PropertyType, value.GetType()))

Source/ViewModels/TabHostViewModel.cs → src/ViewModels/TabHostViewModel.cs

@@ -1,12 +1,13 @@
 using Nkraft.CrossUtility.Patterns;
+using Nkraft.MvvmEssentials.Attributes;
 using Nkraft.MvvmEssentials.Helpers;
 using Nkraft.MvvmEssentials.Services;
 using Nkraft.MvvmEssentials.Services.Navigation;
 using Nkraft.MvvmEssentials.Services.TabbedPages;
 
 namespace Nkraft.MvvmEssentials.ViewModels;
 
-public abstract class TabHostViewModel : PageViewModel, ITabHost
+public abstract partial class TabHostViewModel : PageViewModel, ITabHost
 {
 	protected override void OnInitialized()
 	{
@@ -40,6 +41,7 @@ protected async Task<IResult> SwitchTabAsync<TTabViewModel>(
 
 	protected ITabComponent CurrentTab => Tabs.ElementAt(SelectedTabIndex);
 
+	[Parameter]
 	protected int SelectedTabIndex { get; set; }
 
 	IReadOnlyCollection<ITabComponent> ITabHost.Tabs => Tabs;

Tests/Nkraft.MvvmEssentials.UnitTest.csproj → tests/Nkraft.MvvmEssentials.UnitTest.csproj

@@ -9,9 +9,11 @@
 
     <ItemGroup>
       <ProjectReference Include="..\Source\Nkraft.MvvmEssentials.csproj" />
+      <ProjectReference Include="..\Source\SourceGenerator\Nkraft.MvvmEssentials.SourceGenerator.csproj" />
     </ItemGroup>
 
     <ItemGroup>
+      <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="5.3.0" />
       <PackageReference Include="NSubstitute" Version="6.0.0-rc.1" />
       <PackageReference Include="NUnit" Version="4.6.0" />
       <PackageReference Include="NUnit3TestAdapter" Version="4.6.0" />

tests/ViewModels/NavigationParametersGeneratorTests.cs

@@ -0,0 +1,58 @@
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Nkraft.MvvmEssentials.SourceGenerator;
+using NUnit.Framework;
+
+namespace Nkraft.MvvmEssentials.UnitTest.ViewModels;
+
+[TestFixture]
+public class NavigationParametersGeneratorTests
+{
+    [Test]
+    public void Generator_ShouldGenerateRecord_WhenClassHasParameterAttribute()
+    {
+        var source = """
+                     using Nkraft.MvvmEssentials.ViewModels;
+                     using Nkraft.MvvmEssentials.Attributes;
+
+                     public class MyViewModel : NavigableEntryViewModel
+                     {
+                         [Parameter]
+                         public string Name { get; set; }
+                     }
+                     """;
+
+        var dotNetAssemblies = AppDomain.CurrentDomain.GetAssemblies()
+            .Where(a => !a.IsDynamic && !string.IsNullOrEmpty(a.Location))
+            .Select(a => MetadataReference.CreateFromFile(a.Location));
+
+        var mvvmEssentialsAssembly = typeof(Nkraft.MvvmEssentials.ViewModels.NavigableEntryViewModel).Assembly.Location;
+
+        // 1. Create an EMPTY compilation baseline first
+        var baselineCompilation = CSharpCompilation.Create(
+            assemblyName: "TestAssembly",
+            syntaxTrees: [CSharpSyntaxTree.ParseText(source)],
+            references: [
+                ..dotNetAssemblies, 
+                MetadataReference.CreateFromFile(mvvmEssentialsAssembly) // Ensure this is explicitly linked!
+            ],
+            options: new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
+        );
+
+        var generator = new NavigationParametersGenerator();
+        GeneratorDriver driver = CSharpGeneratorDriver.Create([generator.AsSourceGenerator()]);
+
+        // 2. Run the driver on the empty baseline to initialize its internal cache
+        driver = driver.RunGenerators(baselineCompilation);
+
+        // 3. NOW add your source file to the compilation (creating a delta change)
+        var updatedCompilation = baselineCompilation.AddSyntaxTrees(CSharpSyntaxTree.ParseText(source));
+
+        // 4. Run the driver again. Roslyn sees the new tree and forces the predicate to run!
+        driver = driver.RunGeneratorsAndUpdateCompilation(updatedCompilation, out var outputCompilation, out var diagnostics);
+
+        // Verify results
+        var runResult = driver.GetRunResult();
+        Assert.That(runResult.GeneratedTrees.Length, Is.GreaterThan(0), "No source files were generated!");
+    }
+}