Improved nullable support

src/Controls/src/BindingSourceGen/BindingCodeWriter.cs

@@ -76,6 +76,11 @@ private static bool ShouldUseSetter(BindingMode mode, BindableProperty bindableP
 
 	public void AddBinding(SetBindingInvocationDescription binding)
 	{
+		if (!binding.NullableContextEnabled)
+		{
+			var referenceTypesConditionalAccessTransformer = new ReferenceTypesConditionalAccessTransformer();
+			binding = referenceTypesConditionalAccessTransformer.Transform(binding);
+		}
 		_bindings.Add(binding);
 	}
 
@@ -184,7 +189,7 @@ public void AppendSetBindingInterceptor(int id, SetBindingInvocationDescription
 			Indent();
 
 			Append("handlers: ");
-			AppendHandlersArray(binding.SourceType, binding.Path);
+			AppendHandlersArray(binding);
 			AppendLine(")");
 
 			Unindent();
@@ -234,7 +239,7 @@ private void AppendSetterAction(SetBindingInvocationDescription binding, string
 				AppendLine('}');
 			}
 
-			var setter = Setter.From(binding.SourceType, binding.Path, sourceVariableName, assignedValueExpression);
+			var setter = Setter.From(binding.Path, sourceVariableName, assignedValueExpression);
 			if (setter.PatternMatchingExpressions.Length > 0)
 			{
 				Append("if (");
@@ -274,19 +279,20 @@ private void AppendSetterAction(SetBindingInvocationDescription binding, string
 			}
 		}
 
-		private void AppendHandlersArray(TypeDescription sourceType, EquatableArray<IPathPart> path)
+		private void AppendHandlersArray(SetBindingInvocationDescription binding)
 		{
-			AppendLine($"new Tuple<Func<{sourceType}, object?>, string>[]");
+			AppendLine($"new Tuple<Func<{binding.SourceType}, object?>, string>[]");
 			AppendLine('{');
 
 			Indent();
 
 			string nextExpression = "source";
 			bool forceConditonalAccessToNextPart = false;
-			foreach (var part in path)
+			foreach (var part in binding.Path)
 			{
 				var previousExpression = nextExpression;
 				nextExpression = AccessExpressionBuilder.Build(previousExpression, MaybeWrapInConditionalAccess(part, forceConditonalAccessToNextPart));
+				var isNullableReferenceType = part is MemberAccess memberAccess && !memberAccess.IsValueType;
 				forceConditonalAccessToNextPart = part is Cast;
 
 				// Some parts don't have a property name, so we can't generate a handler for them (for example casts)

src/Controls/src/BindingSourceGen/BindingSourceGenerator.cs

@@ -101,7 +101,8 @@ static BindingDiagnosticsWrapper GetBindingForGeneration(GeneratorSyntaxContext
 			SourceType: BindingGenerationUtilities.CreateTypeNameFromITypeSymbol(lambdaSymbol.Parameters[0].Type, enabledNullable),
 			PropertyType: BindingGenerationUtilities.CreateTypeNameFromITypeSymbol(lambdaTypeInfo.Type, enabledNullable),
 			Path: new EquatableArray<IPathPart>([.. parts]),
-			SetterOptions: DeriveSetterOptions(lambdaBody, context.SemanticModel, enabledNullable));
+			SetterOptions: DeriveSetterOptions(lambdaBody, context.SemanticModel, enabledNullable),
+			NullableContextEnabled: enabledNullable);
 		return new BindingDiagnosticsWrapper(binding, new EquatableArray<DiagnosticInfo>([.. diagnostics]));
 	}
 

src/Controls/src/BindingSourceGen/BindingSourceGeneratorUtilities.cs

@@ -4,6 +4,12 @@ namespace Microsoft.Maui.Controls.BindingSourceGen;
 
 internal static class BindingGenerationUtilities
 {
+
+    internal static bool IsNullableValueType(ITypeSymbol typeInfo) =>
+        typeInfo is INamedTypeSymbol namedTypeSymbol
+            && namedTypeSymbol.IsGenericType
+            && namedTypeSymbol.ConstructedFrom.SpecialType == SpecialType.System_Nullable_T;
+
     internal static bool IsTypeNullable(ITypeSymbol typeInfo, bool enabledNullable)
     {
         if (!enabledNullable && typeInfo.IsReferenceType)
@@ -16,9 +22,7 @@ internal static bool IsTypeNullable(ITypeSymbol typeInfo, bool enabledNullable)
             return true;
         }
 
-        return typeInfo is INamedTypeSymbol namedTypeSymbol
-            && namedTypeSymbol.IsGenericType
-            && namedTypeSymbol.ConstructedFrom.SpecialType == SpecialType.System_Nullable_T;
+        return IsNullableValueType(typeInfo);
     }
 
     internal static TypeDescription CreateTypeNameFromITypeSymbol(ITypeSymbol typeSymbol, bool enabledNullable)

src/Controls/src/BindingSourceGen/BindingTransformer.cs

@@ -0,0 +1,50 @@
+
+namespace Microsoft.Maui.Controls.BindingSourceGen;
+
+public interface IBindingInvocationTransformer
+{
+    SetBindingInvocationDescription Transform(SetBindingInvocationDescription setBindingInvocationDescription);
+}
+
+public class ReferenceTypesConditionalAccessTransformer : IBindingInvocationTransformer
+{
+    public SetBindingInvocationDescription Transform(SetBindingInvocationDescription setBindingInvocationDescription)
+    {
+        var path = TransformPath(setBindingInvocationDescription);
+        return setBindingInvocationDescription with { Path = path };
+    }
+
+    private static EquatableArray<IPathPart> TransformPath(SetBindingInvocationDescription setBindingInvocationDescription)
+    {
+        var newPath = new List<IPathPart>();
+        foreach (var pathPart in setBindingInvocationDescription.Path)
+        {
+            var sourceIsReferenceType = newPath.Count == 0 && !setBindingInvocationDescription.SourceType.IsValueType;
+            var previousPartIsReferenceType = newPath.Count > 0 && PreviousPartIsReferenceType(newPath.Last());
+
+            if (pathPart is not MemberAccess && pathPart is not IndexAccess)
+            {
+                newPath.Add(pathPart);
+            }
+            else if (sourceIsReferenceType || previousPartIsReferenceType)
+            {
+                newPath.Add(new ConditionalAccess(pathPart));
+            }
+            else
+            {
+                newPath.Add(pathPart);
+            }
+        }
+
+        return new EquatableArray<IPathPart>(newPath.ToArray());
+
+        static bool PreviousPartIsReferenceType(IPathPart previousPathPart) =>
+            previousPathPart switch
+            {
+                MemberAccess memberAccess => !memberAccess.IsValueType,
+                IndexAccess indexAccess => !indexAccess.IsValueType,
+                ConditionalAccess { Part: var inner } => PreviousPartIsReferenceType(inner),
+                _ => false,
+            };
+    }
+}

src/Controls/src/BindingSourceGen/GeneratorDataModels.cs

@@ -18,7 +18,8 @@ public sealed record SetBindingInvocationDescription(
 	TypeDescription SourceType,
 	TypeDescription PropertyType,
 	EquatableArray<IPathPart> Path,
-	SetterOptions SetterOptions);
+	SetterOptions SetterOptions,
+	bool NullableContextEnabled);
 
 public sealed record SourceCodeLocation(string FilePath, TextSpan TextSpan, LinePositionSpan LineSpan)
 {
@@ -54,23 +55,28 @@ public override string ToString()
 
 public sealed record SetterOptions(bool IsWritable, bool AcceptsNullValue = false);
 
-public sealed record MemberAccess(string MemberName) : IPathPart
+public sealed record MemberAccess(string MemberName, bool IsValueType = false) : IPathPart
 {
-	public string? PropertyName => MemberName;
+	public string PropertyName => MemberName;
 
 	public bool Equals(IPathPart other)
 	{
-		return other is MemberAccess memberAccess && MemberName == memberAccess.MemberName;
+		return other is MemberAccess memberAccess
+			&& MemberName == memberAccess.MemberName
+			&& IsValueType == memberAccess.IsValueType;
 	}
 }
 
-public sealed record IndexAccess(string DefaultMemberName, object Index) : IPathPart
+public sealed record IndexAccess(string DefaultMemberName, object Index, bool IsValueType = false) : IPathPart
 {
 	public string? PropertyName => $"{DefaultMemberName}[{Index}]";
 
 	public bool Equals(IPathPart other)
 	{
-		return other is IndexAccess indexAccess && DefaultMemberName == indexAccess.DefaultMemberName && Index.Equals(indexAccess.Index);
+		return other is IndexAccess indexAccess
+			&& DefaultMemberName == indexAccess.DefaultMemberName
+			&& Index.Equals(indexAccess.Index)
+			&& IsValueType == indexAccess.IsValueType;
 	}
 }
 

src/Controls/src/BindingSourceGen/PathParser.cs

@@ -41,7 +41,9 @@ BinaryExpressionSyntax asExpression when asExpression.Kind() == SyntaxKind.AsExp
         }
 
         var member = memberAccess.Name.Identifier.Text;
-        IPathPart part = new MemberAccess(member);
+        var typeInfo = Context.SemanticModel.GetTypeInfo(memberAccess).Type;
+        var isReferenceType = typeInfo?.IsReferenceType ?? false;
+        IPathPart part = new MemberAccess(member, !isReferenceType);
         parts.Add(part);
         return (diagnostics, parts);
     }
@@ -55,12 +57,13 @@ BinaryExpressionSyntax asExpression when asExpression.Kind() == SyntaxKind.AsExp
         }
 
         var elementAccessSymbol = Context.SemanticModel.GetSymbolInfo(elementAccess).Symbol;
-        var (elementAccessDiagnostics, elementAccessParts) = HandleElementAccessSymbol(elementAccessSymbol, elementAccess.ArgumentList.Arguments, elementAccess.GetLocation());
+        var elementType = Context.SemanticModel.GetTypeInfo(elementAccess).Type;
+
+        var (elementAccessDiagnostics, elementAccessParts) = CreateIndexAccess(elementAccessSymbol, elementType, elementAccess.ArgumentList.Arguments, elementAccess.GetLocation());
         if (elementAccessDiagnostics.Length > 0)
         {
             return (elementAccessDiagnostics, elementAccessParts);
         }
-
         parts.AddRange(elementAccessParts);
         return (diagnostics, parts);
     }
@@ -86,7 +89,9 @@ BinaryExpressionSyntax asExpression when asExpression.Kind() == SyntaxKind.AsExp
     private (EquatableArray<DiagnosticInfo> diagnostics, List<IPathPart> parts) HandleMemberBindingExpression(MemberBindingExpressionSyntax memberBinding)
     {
         var member = memberBinding.Name.Identifier.Text;
-        IPathPart part = new MemberAccess(member);
+        var typeInfo = Context.SemanticModel.GetTypeInfo(memberBinding).Type;
+        var isReferenceType = typeInfo?.IsReferenceType ?? false;
+        IPathPart part = new MemberAccess(member, !isReferenceType);
         part = new ConditionalAccess(part);
 
         return ([], new List<IPathPart>([part]));
@@ -95,7 +100,9 @@ BinaryExpressionSyntax asExpression when asExpression.Kind() == SyntaxKind.AsExp
     private (EquatableArray<DiagnosticInfo> diagnostics, List<IPathPart> parts) HandleElementBindingExpression(ElementBindingExpressionSyntax elementBinding)
     {
         var elementAccessSymbol = Context.SemanticModel.GetSymbolInfo(elementBinding).Symbol;
-        var (elementAccessDiagnostics, elementAccessParts) = HandleElementAccessSymbol(elementAccessSymbol, elementBinding.ArgumentList.Arguments, elementBinding.GetLocation());
+        var elementType = Context.SemanticModel.GetTypeInfo(elementBinding).Type;
+
+        var (elementAccessDiagnostics, elementAccessParts) = CreateIndexAccess(elementAccessSymbol, elementType, elementBinding.ArgumentList.Arguments, elementBinding.GetLocation());
         if (elementAccessDiagnostics.Length > 0)
         {
             return (elementAccessDiagnostics, elementAccessParts);
@@ -147,7 +154,7 @@ BinaryExpressionSyntax asExpression when asExpression.Kind() == SyntaxKind.AsExp
         return (new EquatableArray<DiagnosticInfo>([DiagnosticsFactory.UnableToResolvePath(Context.Node.GetLocation())]), new List<IPathPart>());
     }
 
-    private (EquatableArray<DiagnosticInfo>, List<IPathPart>) HandleElementAccessSymbol(ISymbol? elementAccessSymbol, SeparatedSyntaxList<ArgumentSyntax> argumentList, Location location)
+    private (EquatableArray<DiagnosticInfo>, List<IPathPart>) CreateIndexAccess(ISymbol? elementAccessSymbol, ITypeSymbol? typeSymbol, SeparatedSyntaxList<ArgumentSyntax> argumentList, Location location)
     {
         if (argumentList.Count != 1)
         {
@@ -162,7 +169,8 @@ BinaryExpressionSyntax asExpression when asExpression.Kind() == SyntaxKind.AsExp
         }
 
         var name = GetIndexerName(elementAccessSymbol);
-        IPathPart part = new IndexAccess(name, indexValue);
+        var isReferenceType = typeSymbol?.IsReferenceType ?? false;
+        IPathPart part = new IndexAccess(name, indexValue, !isReferenceType);
 
         return ([], [part]);
     }

src/Controls/src/BindingSourceGen/SetterBuilder.cs

@@ -3,32 +3,22 @@ namespace Microsoft.Maui.Controls.BindingSourceGen;
 public sealed record Setter(string[] PatternMatchingExpressions, string AssignmentStatement)
 {
     public static Setter From(
-        TypeDescription sourceTypeDescription,
-        EquatableArray<IPathPart> path,
+        IEnumerable<IPathPart> path,
         string sourceVariableName = "source",
         string assignedValueExpression = "value")
     {
         var builder = new SetterBuilder(sourceVariableName, assignedValueExpression);
 
-        if (path.Length > 0)
+        foreach (var part in path)
         {
-            if (sourceTypeDescription.IsNullable)
-            {
-                builder.AddIsExpression("{}");
-            }
-
-            foreach (var part in path)
-            {
-                builder.AddPart(part);
-            }
+            builder.AddPart(part);
         }
 
         return builder.Build();
     }
 
     private sealed class SetterBuilder
     {
-        private readonly string _sourceVariableName;
         private readonly string _assignedValueExpression;
 
         private string _expression;
@@ -38,9 +28,7 @@ private sealed class SetterBuilder
 
         public SetterBuilder(string sourceVariableName, string assignedValueExpression)
         {
-            _sourceVariableName = sourceVariableName;
             _assignedValueExpression = assignedValueExpression;
-
             _expression = sourceVariableName;
         }
 

src/Controls/tests/BindingSourceGen.UnitTests/BindingCodeWriterTests.cs

@@ -19,7 +19,8 @@ public void BuildsWholeDocument()
                 new ConditionalAccess(new MemberAccess("B")),
                 new ConditionalAccess(new MemberAccess("C")),
             ]),
-            SetterOptions: new(IsWritable: true, AcceptsNullValue: false)));
+            SetterOptions: new(IsWritable: true, AcceptsNullValue: false),
+            NullableContextEnabled: true));
 
         var code = codeWriter.GenerateCode();
         AssertExtensions.CodeIsEqual(
@@ -140,7 +141,8 @@ public void CorrectlyFormatsSimpleBinding()
                 new ConditionalAccess(new MemberAccess("B")),
                 new ConditionalAccess(new MemberAccess("C")),
             ]),
-            SetterOptions: new(IsWritable: true, AcceptsNullValue: false)));
+            SetterOptions: new(IsWritable: true, AcceptsNullValue: false),
+            NullableContextEnabled: true));
 
         var code = codeBuilder.ToString();
         AssertExtensions.CodeIsEqual(
@@ -210,7 +212,8 @@ public void CorrectlyFormatsBindingWithoutAnyNullablesInPath()
                 new MemberAccess("B"),
                 new MemberAccess("C"),
             ]),
-            SetterOptions: new(IsWritable: true, AcceptsNullValue: false)));
+            SetterOptions: new(IsWritable: true, AcceptsNullValue: false),
+            NullableContextEnabled: true));
 
         var code = codeBuilder.ToString();
         AssertExtensions.CodeIsEqual(
@@ -276,7 +279,8 @@ public void CorrectlyFormatsBindingWithoutSetter()
                 new MemberAccess("B"),
                 new MemberAccess("C"),
             ]),
-            SetterOptions: new(IsWritable: false)));
+            SetterOptions: new(IsWritable: false),
+            NullableContextEnabled: true));
 
         var code = codeBuilder.ToString();
         AssertExtensions.CodeIsEqual(
@@ -339,7 +343,8 @@ public void CorrectlyFormatsBindingWithIndexers()
                 new ConditionalAccess(new IndexAccess("Indexer", "Abc")),
                 new IndexAccess("Item", 0),
             ]),
-            SetterOptions: new(IsWritable: true, AcceptsNullValue: false)));
+            SetterOptions: new(IsWritable: true, AcceptsNullValue: false),
+            NullableContextEnabled: true));
 
         var code = codeBuilder.ToString();
         AssertExtensions.CodeIsEqual(
@@ -417,7 +422,8 @@ public void CorrectlyFormatsBindingWithCasts()
                 new Cast(new TypeDescription("Z", IsValueType: true, IsNullable: true, IsGenericParameter: false)),
                 new ConditionalAccess(new MemberAccess("D")),
             ]),
-            SetterOptions: new(IsWritable: true, AcceptsNullValue: false)));
+            SetterOptions: new(IsWritable: true, AcceptsNullValue: false),
+            NullableContextEnabled: true));
 
         var code = codeBuilder.ToString();