From 6d950d8e15fe8624acc717e5fdeec6bde1edab03 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Thu, 18 Jun 2026 23:55:34 -0700
Subject: [PATCH] Compiled Bindings: Fix unpredictable binding to method
 selection (#21617)

* Fix unpredictable binding to method selection (compiled bindings)

* Adjust tests

* Add more test cases
---
 .../XamlIlBindingPathHelper.cs                | 21 ++++++++++--
 .../XamlIlTrampolineBuilder.cs                | 21 ++----------
 .../CompiledBindingExtensionTests.cs          | 34 ++++++++++---------
 3 files changed, 40 insertions(+), 36 deletions(-)

diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlBindingPathHelper.cs b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlBindingPathHelper.cs
index e83807ea93..84af961431 100644
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlBindingPathHelper.cs
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlBindingPathHelper.cs
@@ -210,9 +210,26 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
                             {
                                 nodes.Add(new XamlIlClrPropertyPathElementNode(clrProperty, propName.AcceptsNull));
                             }
-                            else if (GetAllDefinedMethods(targetType).FirstOrDefault(m => m.Name == propName.PropertyName) is IXamlMethod method)
+                            else if (GetAllDefinedMethods(targetType)
+                                         .Where(p => p.Name == propName.PropertyName)
+                                         .OrderByDescending(m => m.Parameters.Count)
+                                         .ToArray()
+                                     is { Length: > 0 } methodCandidates)
                             {
-                                nodes.Add(new XamlIlClrMethodPathElementNode(method, context.Configuration.WellKnownTypes.Delegate, propName.AcceptsNull));
+                                var objType = context.Configuration.WellKnownTypes.Object;
+                                var candidate = methodCandidates
+                                    .FirstOrDefault(m => m.Parameters.Count == 0
+                                                         || (m.Parameters.Count == 1 &&
+                                                             m.Parameters[0].Equals(objType)));
+                                if (candidate is null)
+                                {
+                                    throw new XamlX.XamlTransformException(
+                                        $"Unable to resolve method of name '{propName.PropertyName}' on type '{targetType}'." +
+                                        $"Expected method with no parameters or a single object overload.",
+                                        lineInfo);
+                                }
+            
+                                nodes.Add(new XamlIlClrMethodPathElementNode(candidate, context.Configuration.WellKnownTypes.Delegate, propName.AcceptsNull));
                             }
                             else
                             {
diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlTrampolineBuilder.cs b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlTrampolineBuilder.cs
index ae26aec993..5245fa7d3c 100644
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlTrampolineBuilder.cs
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlTrampolineBuilder.cs
@@ -48,24 +48,9 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
             }
             if (executeMethod.Parameters.Count != 0)
             {
-                Debug.Assert(executeMethod.Parameters.Count == 1);
-                if (executeMethod.Parameters[0] != context.Configuration.WellKnownTypes.Object)
-                {
-                    var convertedValue = gen.DefineLocal(context.Configuration.WellKnownTypes.Object);
-                    gen.Ldtype(executeMethod.Parameters[0])
-                        .Ldarg(1)
-                        .EmitCall(context.Configuration.WellKnownTypes.CultureInfo.GetMethod(m => m.Name == "get_CurrentCulture"))
-                        .Ldloca(convertedValue)
-                        .EmitCall(
-                            context.GetAvaloniaTypes().TypeUtilities.GetMethod(m => m.Name == "TryConvert"),
-                            swallowResult: true)
-                        .Ldloc(convertedValue)
-                        .Unbox_Any(executeMethod.Parameters[0]);
-                }
-                else
-                {
-                    gen.Ldarg(1);
-                }
+                Debug.Assert(executeMethod.Parameters.Count == 1
+                             && executeMethod.Parameters[0] == context.Configuration.WellKnownTypes.Object);
+                gen.Ldarg(1);
             }
             gen.EmitCall(executeMethod, swallowResult: true);
             gen.Ret();
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs
index 99a79ded75..d3374ce8ad 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs
@@ -1863,8 +1863,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
     <StackPanel>
         <ContentControl Content='{CompiledBinding Action}' Name='action' />
         <ContentControl Content='{CompiledBinding Func}' Name='func' />
-        <ContentControl Content='{CompiledBinding Action16}' Name='action16' />
-        <ContentControl Content='{CompiledBinding Func16}' Name='func16' />
+        <ContentControl Content='{CompiledBinding Func2}' Name='func2' />
         <ContentControl Content='{CompiledBinding CustomDelegateTypeVoid}' Name='customvoid' />
         <ContentControl Content='{CompiledBinding CustomDelegateTypeInt}' Name='customint' />
     </StackPanel>
@@ -1873,9 +1872,8 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
                 window.DataContext = new MethodDataContext();
 
                 Assert.IsAssignableFrom(typeof(Action), window.GetControl<ContentControl>("action").Content);
-                Assert.IsAssignableFrom(typeof(Func<int>), window.GetControl<ContentControl>("func").Content);
-                Assert.IsAssignableFrom(typeof(Action<int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, int>), window.GetControl<ContentControl>("action16").Content);
-                Assert.IsAssignableFrom(typeof(Func<int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, int>), window.GetControl<ContentControl>("func16").Content);
+                Assert.IsAssignableFrom(typeof(Func<object>), window.GetControl<ContentControl>("func").Content);
+                Assert.IsAssignableFrom(typeof(Func<object, object>), window.GetControl<ContentControl>("func2").Content);
                 Assert.True(typeof(Delegate).IsAssignableFrom(window.GetControl<ContentControl>("customvoid").Content!.GetType()));
                 Assert.True(typeof(Delegate).IsAssignableFrom(window.GetControl<ContentControl>("customint").Content!.GetType()));
             }
@@ -1906,17 +1904,20 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
             }
         }
 
-        [Fact]
-        public void Binding_Method_With_Parameter_To_Command_Works()
+        [Theory]
+        [InlineData("5")]
+        [InlineData("hello")]
+        [InlineData(null)]
+        public void Binding_Method_With_Parameter_To_Command_Works(string? parameter)
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
-                var xaml = @"
+                var xaml = $@"
 <Window xmlns='https://github.com/avaloniaui'
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
         xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
         x:DataType='local:MethodAsCommandDataContext'>
-    <Button Name='button' Command='{CompiledBinding Method1}' CommandParameter='5'/>
+    <Button Name='button' Command='{{CompiledBinding Method1}}' CommandParameter='{ parameter ?? "{x:Null}" }'/>
 </Window>";
                 var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
                 var button = window.GetControl<Button>("button");
@@ -1927,7 +1928,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
 
                 Assert.NotNull(button.Command);
                 PerformClick(button);
-                Assert.Equal("Called 5", vm.Value);
+                Assert.Equal("Called " + parameter, vm.Value);
             }
         }
 
@@ -2533,12 +2534,11 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
     {
         public void Action() { }
 
-        public int Func() => 1;
+        public object Func() => 1;
+        public object Func2(object i) => i;
 
-        public void Action16(int i, int i2, int i3, int i4, int i5, int i6, int i7, int i8, int i9, int i10, int i11, int i12, int i13, int i14, int i15, int i16) { }
-        public int Func16(int i, int i2, int i3, int i4, int i5, int i6, int i7, int i8, int i9, int i10, int i11, int i12, int i13, int i14, int i15, int i16) => i;
-        public void CustomDelegateTypeVoid(int i, int i2, int i3, int i4, int i5, int i6, int i7, int i8, int i9, int i10, int i11, int i12, int i13, int i14, int i15, int i16, int i17) { }
-        public int CustomDelegateTypeInt(int i, int i2, int i3, int i4, int i5, int i6, int i7, int i8, int i9, int i10, int i11, int i12, int i13, int i14, int i15, int i16, int i17) => i;
+        public void CustomDelegateTypeVoid(object i) { }
+        public object CustomDelegateTypeInt(object i) => i;
     }
 
     public class MethodAsCommandDataContext : INotifyPropertyChanged
@@ -2546,7 +2546,9 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
         public event PropertyChangedEventHandler? PropertyChanged;
 
         public string Method() => Value = "Called";
-        public string Method1(int i) => Value = $"Called {i}";
+        public string Method1() => Value = "Called";
+        public string Method1(int i) => throw new InvalidOperationException("Binding to method with typed parameters is not supported");
+        public string Method1(object i) => Value = $"Called {i}";
         public string Method2(int i, int j) => Value = $"Called {i},{j}";
         public string Value { get; private set; } = "Not called";