[RGen] Add the validation for weak delegates.

src/rgen/Microsoft.Macios.Bindings.Analyzer/Resources.resx

@@ -430,4 +430,17 @@
         <value>Wrong property declaration</value>
     </data>
 
+    <!-- RBI0032 -->
+
+    <data name="RBI0032Description" xml:space="preserve">
+        <value>A weak delegate has to have a strong delegate name if it does not start with 'Weak'.</value>
+    </data>
+    <data name="RBI0032MessageFormat" xml:space="preserve">
+        <value>The weak delegate '{0}' is missing a strong delegate name, provide one or use the 'Weak' prefix</value>
+        <comment>{0} is the name of the property that does not start with 'Weak'.</comment>
+    </data>
+    <data name="RBI0032Title" xml:space="preserve">
+        <value>Wrong weak delegate</value>
+    </data>
+
 </root>

src/rgen/Microsoft.Macios.Bindings.Analyzer/RgenDiagnostics.cs

@@ -481,4 +481,19 @@ public static class RgenDiagnostics {
 		description: new LocalizableResourceString (nameof (Resources.RBI0031Description), Resources.ResourceManager,
 			typeof (Resources))
 	);
+
+	/// <summary>
+	/// Diagnostic descriptor for when a weak delegate does not start with "Weak".
+	/// </summary>
+	internal static readonly DiagnosticDescriptor RBI0032 = new (
+		"RBI0032",
+		new LocalizableResourceString (nameof (Resources.RBI0032Title), Resources.ResourceManager, typeof (Resources)),
+		new LocalizableResourceString (nameof (Resources.RBI0032MessageFormat), Resources.ResourceManager,
+			typeof (Resources)),
+		"Usage",
+		DiagnosticSeverity.Warning,
+		isEnabledByDefault: true,
+		description: new LocalizableResourceString (nameof (Resources.RBI0032Description), Resources.ResourceManager,
+			typeof (Resources))
+	);
 }

src/rgen/Microsoft.Macios.Bindings.Analyzer/Validators/PropertyValidator.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using System;
 using System.Collections.Immutable;
 using Microsoft.CodeAnalysis;
 using Microsoft.Macios.Generator.Context;
@@ -70,6 +71,32 @@ internal static bool AccessorIsValid ((string PropertyName, Accessor Accessor) d
 			out diagnostics);
 	}
 
+	/// <summary>
+	/// Validates that a weak delegate property's name starts with "Weak" or that it has a corresponding strong delegate name defined.
+	/// </summary>
+	/// <param name="data">The property to validate.</param>
+	/// <param name="context">The root context for validation.</param>
+	/// <param name="diagnostic">When this method returns, contains a diagnostic if the property name is invalid; otherwise, an empty array.</param>
+	/// <param name="location">The code location to be used for the diagnostics.</param>
+	/// <returns><c>true</c> if the property is not a weak delegate or if its name is valid; otherwise, <c>false</c>.</returns>
+	internal static bool WeakPropertyNameStartsWithWeak (Property data, RootContext context,
+		out ImmutableArray<Diagnostic> diagnostic, Location? location)
+	{
+		diagnostic = ImmutableArray<Diagnostic>.Empty;
+		if (data.IsWeakDelegate
+			&& !data.Name.StartsWith ("Weak", StringComparison.Ordinal)
+			&& string.IsNullOrEmpty (data.ExportPropertyData.StrongDelegateName)) {
+			// if the property is weak, it must start with Weak
+			diagnostic = [Diagnostic.Create (
+				descriptor: RBI0032,
+				location: data.Location,
+				messageArgs: data.Name)];
+			return false;
+		}
+		// we do not care about non-weak properties
+		return true;
+	}
+
 	/// <summary>
 	/// Initializes a new instance of the <see cref="PropertyValidator"/> class.
 	/// </summary>
@@ -96,5 +123,10 @@ public PropertyValidator () : base (p => p.Location)
 			descriptor: [RBI0018, RBI0019, RBI0029],
 			validation: AccessorIsValid,
 			propertyName: "setter");
+
+		// if a property is weak ensure that it starts the name with Weak or set the strondelegatename in the 
+		// export property data
+		AddGlobalStrategy (RBI0032, WeakPropertyNameStartsWithWeak);
 	}
+
 }

tests/rgen/Microsoft.Macios.Bindings.Analyzer.Tests/Validators/PropertyOrFieldValidatorTests.cs

@@ -152,4 +152,12 @@ public void ValidateValidPropertyTests ()
 	[Fact]
 	public void ValidateValidFieldPropertyTests ()
 		=> testLogic.ValidateValidFieldPropertyTestsImpl ();
+
+	[Theory]
+	[InlineData ("MyProperty", false, null, 0)] // Not weak, should pass
+	[InlineData ("WeakMyProperty", true, null, 0)] // Weak, starts with "Weak", should pass
+	[InlineData ("MyProperty", true, "StrongDelegateName", 0)] // Weak, doesn't start with "Weak", but has StrongDelegateName, should pass
+	[InlineData ("MyProperty", true, null, 1)] // Weak, doesn't start with "Weak", no StrongDelegateName, should fail
+	public void WeakPropertyNameStartsWithWeakTests (string propertyName, bool isWeak, string? strongDelegateName, int expectedDiagnosticsCount)
+		=> testLogic.WeakPropertyNameStartsWithWeakTestsImpl (propertyName, isWeak, strongDelegateName, expectedDiagnosticsCount);
 }

tests/rgen/Microsoft.Macios.Bindings.Analyzer.Tests/Validators/PropertyValidatorTestLogic.cs

@@ -51,7 +51,8 @@ Property CreateProperty (string name = "TestProperty",
 		string? getterSelector = null,
 		string? setterSelector = null,
 		bool hasGetter = true,
-		bool hasSetter = true)
+		bool hasSetter = true,
+		string? strongDelegateName = null)
 	{
 		var modifiers = ImmutableArray.CreateBuilder<SyntaxToken> ();
 		modifiers.Add (SyntaxFactory.Token (SyntaxKind.PublicKeyword));
@@ -103,7 +104,9 @@ Property CreateProperty (string name = "TestProperty",
 			accessors: accessors.ToImmutable ()
 		) {
 			ExportPropertyData = new ExportData<ObjCBindings.Property> (propertySelector,
-				argumentSemantic, propertyFlags)
+				argumentSemantic, propertyFlags) {
+				StrongDelegateName = strongDelegateName
+			}
 		};
 	}
 
@@ -318,5 +321,17 @@ public void ValidateValidFieldPropertyTestsImpl ()
 		var result = validator.ValidateAll (property, context);
 		Assert.Empty (result);
 	}
-}
 
+	public void WeakPropertyNameStartsWithWeakTestsImpl (string propertyName, bool isWeak, string? strongDelegateName, int expectedDiagnosticsCount)
+	{
+		var flags = isWeak ? ObjCBindings.Property.WeakDelegate : ObjCBindings.Property.Default;
+		var property = CreateProperty (name: propertyName, propertyFlags: flags, strongDelegateName: strongDelegateName);
+		var result = validator.ValidateAll (property, context);
+		var totalDiagnostics = result.Values.Sum (x => x.Count);
+		Assert.Equal (expectedDiagnosticsCount, totalDiagnostics);
+		if (expectedDiagnosticsCount > 0) {
+			var diagnostic = result.Values.SelectMany (x => x).First ();
+			Assert.Equal ("RBI0032", diagnostic.Id);
+		}
+	}
+}

tests/rgen/Microsoft.Macios.Bindings.Analyzer.Tests/Validators/PropertyValidatorTests.cs

@@ -88,4 +88,12 @@ public void PropertyAccessorPresenceTests (bool hasGetter, bool hasSetter, int e
 	[InlineData (false, "invalid getter", "invalid setter:", 3)] // Not partial and multiple issues
 	public void CombinedValidationTests (bool isPartial, string? getterSelector, string? setterSelector, int expectedDiagnosticsCount)
 		=> testLogic.CombinedPropertyValidationTestsImpl (isPartial, getterSelector, setterSelector, expectedDiagnosticsCount);
+
+	[Theory]
+	[InlineData ("MyProperty", false, null, 0)] // Not weak, should pass
+	[InlineData ("WeakMyProperty", true, null, 0)] // Weak, starts with "Weak", should pass
+	[InlineData ("MyProperty", true, "StrongDelegateName", 0)] // Weak, doesn't start with "Weak", but has StrongDelegateName, should pass
+	[InlineData ("MyProperty", true, null, 1)] // Weak, doesn't start with "Weak", no StrongDelegateName, should fail
+	public void WeakPropertyNameStartsWithWeakTests (string propertyName, bool isWeak, string? strongDelegateName, int expectedDiagnosticsCount)
+		=> testLogic.WeakPropertyNameStartsWithWeakTestsImpl (propertyName, isWeak, strongDelegateName, expectedDiagnosticsCount);
 }