Fix IRecipient generator for partial recipient declarations

Author: Sergio0694

CommunityToolkit.Mvvm.SourceGenerators/Messaging/IMessengerRegisterAllGenerator.cs

@@ -36,10 +36,15 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             .Select(static (item, _) => (item, Interfaces: Execute.GetInterfaces(item)))
             .Where(static item => !item.Interfaces.IsEmpty);
 
-        // Get the recipient info for all target types
+        // Get the recipient info for all target types. This pipeline step also needs to filter out
+        // duplicate recipient definitions (it might happen if a recipient has partial declarations)
         IncrementalValuesProvider<RecipientInfo> recipientInfo =
             typeAndInterfaceSymbols
             .Select(static (item, _) => Execute.GetInfo(item.Type, item.Interfaces))
+            .WithComparer(RecipientInfo.Comparer.Default)
+            .Collect()
+            .Select(static (item, _) => item.Distinct(RecipientInfo.EqualityComparerByFilenameHint))
+            .SelectMany(static (item, _) => item)
             .WithComparer(RecipientInfo.Comparer.Default);
 
         // Check whether the header file is needed

CommunityToolkit.Mvvm.SourceGenerators/Messaging/Models/RecipientInfo.cs

@@ -22,6 +22,11 @@ internal sealed record RecipientInfo(
     string TypeName,
     ImmutableArray<string> MessageTypes)
 {
+    /// <summary>
+    /// Gets an <see cref="IEqualityComparer{T}"/> implementation only matching by <see cref="FilenameHint"/>.
+    /// </summary>
+    public static IEqualityComparer<RecipientInfo> EqualityComparerByFilenameHint { get; } = new FilenameHintComparer();
+
     /// <summary>
     /// An <see cref="IEqualityComparer{T}"/> implementation for <see cref="RecipientInfo"/>.
     /// </summary>
@@ -44,4 +49,22 @@ protected override bool AreEqual(RecipientInfo x, RecipientInfo y)
                 x.MessageTypes.SequenceEqual(y.MessageTypes);
         }
     }
+
+    /// <summary>
+    /// An <see cref="IEqualityComparer{T}"/> implementation only matching by <see cref="FilenameHint"/>.
+    /// </summary>
+    private sealed class FilenameHintComparer : IEqualityComparer<RecipientInfo>
+    {
+        /// <inheritdoc/>
+        public bool Equals(RecipientInfo x, RecipientInfo y)
+        {
+            return x.FilenameHint == y.FilenameHint;
+        }
+
+        /// <inheritdoc/>
+        public int GetHashCode(RecipientInfo obj)
+        {
+            return obj.FilenameHint.GetHashCode();
+        }
+    }
 }

tests/CommunityToolkit.Mvvm.UnitTests/Test_IRecipientGenerator.cs

@@ -16,11 +16,11 @@ public partial class Test_IRecipientGenerator
     [TestMethod]
     public void Test_IRecipientGenerator_GeneratedRegistration()
     {
-        StrongReferenceMessenger? messenger = new();
-        RecipientWithSomeMessages? recipient = new();
+        StrongReferenceMessenger messenger = new();
+        RecipientWithSomeMessages recipient = new();
 
-        MessageA? messageA = new();
-        MessageB? messageB = new();
+        MessageA messageA = new();
+        MessageB messageB = new();
 
         Action<IMessenger, object, int> registrator = Messaging.__Internals.__IMessengerExtensions.CreateAllMessagesRegistratorWithToken<int>(recipient);
 
@@ -43,6 +43,15 @@ public void Test_IRecipientGenerator_GeneratedRegistration()
         Assert.AreSame(recipient.B, messageB);
     }
 
+    [TestMethod]
+    public void Test_IRecipientGenerator_TypeWithMultipleClassDeclarations()
+    {
+        RecipientWithMultipleClassDeclarations recipient = new();
+
+        // This test really just needs to verify this compiles and executes normally
+        _ = Messaging.__Internals.__IMessengerExtensions.CreateAllMessagesRegistratorWithToken<int>(recipient);
+    }
+
     public sealed class RecipientWithSomeMessages :
         IRecipient<MessageA>,
         IRecipient<MessageB>
@@ -69,4 +78,17 @@ public sealed class MessageA
     public sealed class MessageB
     {
     }
+
+    public sealed partial class RecipientWithMultipleClassDeclarations : IRecipient<MessageA>
+    {
+        public void Receive(MessageA message)
+        {
+        }
+    }
+
+    // This empty partial type declarations needs to be present to ensure the generator
+    // correctly handles cases where the source type has multiple class declarations.
+    partial class RecipientWithMultipleClassDeclarations
+    {
+    }
 }