Enable implementing OnActivated/OnDeactivated with [ObservableRecipient]

Author: Sergio0694

CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/Models/ObservableRecipientInfo.cs

@@ -12,9 +12,13 @@ namespace CommunityToolkit.Mvvm.SourceGenerators.ComponentModel.Models;
 /// <param name="IsAbstract">Whether or not the target type is abstract.</param>
 /// <param name="IsObservableValidator">Whether or not the target type inherits from <c>ObservableValidator</c>.</param>
 /// <param name="IsRequiresUnreferencedCodeAttributeAvailable">Whether or not the <c>RequiresUnreferencedCodeAttribute</c> type is available.</param>
+/// <param name="HasOnActivatedMethod">Whether the target type has a custom <c>OnActivated()</c> method.</param>
+/// <param name="HasOnDeactivatedMethod">Whether the target type has a custom <c>OnDeactivated()</c> method.</param>
 public sealed record ObservableRecipientInfo(
     string TypeName,
     bool HasExplicitConstructors,
     bool IsAbstract,
     bool IsObservableValidator,
-    bool IsRequiresUnreferencedCodeAttributeAvailable);
+    bool IsRequiresUnreferencedCodeAttributeAvailable,
+    bool HasOnActivatedMethod,
+    bool HasOnDeactivatedMethod);

CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/ObservableRecipientGenerator.cs

@@ -40,13 +40,17 @@ static ObservableRecipientInfo GetInfo(INamedTypeSymbol typeSymbol, AttributeDat
             bool hasExplicitConstructors = !(typeSymbol.InstanceConstructors.Length == 1 && typeSymbol.InstanceConstructors[0] is { Parameters.IsEmpty: true, IsImplicitlyDeclared: true });
             bool isAbstract = typeSymbol.IsAbstract;
             bool isObservableValidator = typeSymbol.InheritsFrom("global::CommunityToolkit.Mvvm.ComponentModel.ObservableValidator");
+            bool hasOnActivatedMethod = typeSymbol.GetMembers().Any(m => m is IMethodSymbol { Parameters.IsEmpty: true, Name: "OnActivated" });
+            bool hasOnDeactivatedMethod = typeSymbol.GetMembers().Any(m => m is IMethodSymbol { Parameters.IsEmpty: true, Name: "OnDeactivated" });
 
             return new(
                 typeName,
                 hasExplicitConstructors,
                 isAbstract,
                 isObservableValidator,
-                isRequiresUnreferencedCodeAttributeAvailable);
+                isRequiresUnreferencedCodeAttributeAvailable,
+                hasOnActivatedMethod,
+                hasOnDeactivatedMethod);
         }
 
         // Check whether [RequiresUnreferencedCode] is available
@@ -119,8 +123,38 @@ protected override ImmutableArray<MemberDeclarationSyntax> FilterDeclaredMembers
             }
         }
 
-        MemberDeclarationSyntax RemoveRequiresUnreferencedCodeAttributeIfNeeded(MemberDeclarationSyntax member)
+        MemberDeclarationSyntax FixupFilteredMemberDeclaration(MemberDeclarationSyntax member)
         {
+            // Make OnActivated partial if the type already has the method
+            if (info.HasOnActivatedMethod &&
+                member is MethodDeclarationSyntax { Identifier.ValueText: "OnActivated" } onActivatdMethod)
+            {
+                SyntaxNode attributeNode =
+                    member
+                    .DescendantNodes()
+                    .OfType<AttributeListSyntax>()
+                    .First(node => node.Attributes[0].Name is QualifiedNameSyntax { Right: IdentifierNameSyntax { Identifier.ValueText: "RequiresUnreferencedCode" } });
+
+                return
+                    onActivatdMethod
+                    .RemoveNode(attributeNode, SyntaxRemoveOptions.KeepExteriorTrivia)!
+                    .AddModifiers(Token(SyntaxKind.PartialKeyword))
+                    .WithBody(null)
+                    .WithSemicolonToken(Token(SyntaxKind.SemicolonToken));
+            }
+
+            // Make OnDeactivated partial if the type already has the method
+            if (info.HasOnDeactivatedMethod &&
+                member is MethodDeclarationSyntax { Identifier.ValueText: "OnDeactivated" } onDeactivatedMethod)
+            {
+                return
+                    onDeactivatedMethod
+                    .AddModifiers(Token(SyntaxKind.PartialKeyword))
+                    .WithBody(null)
+                    .WithSemicolonToken(Token(SyntaxKind.SemicolonToken));
+            }
+
+            // Remove [RequiresUnreferencedCode] if the attribute is not available
             if (!info.IsRequiresUnreferencedCodeAttributeAvailable &&
                 member is PropertyDeclarationSyntax { Identifier.ValueText: "IsActive" } or MethodDeclarationSyntax { Identifier.ValueText: "OnActivated" })
             {
@@ -143,7 +177,7 @@ MemberDeclarationSyntax RemoveRequiresUnreferencedCodeAttributeIfNeeded(MemberDe
             {
                 if (member is not MethodDeclarationSyntax { Identifier.ValueText: "SetProperty" })
                 {
-                    builder.Add(RemoveRequiresUnreferencedCodeAttributeIfNeeded(member));
+                    builder.Add(FixupFilteredMemberDeclaration(member));
                 }
             }
 
@@ -153,7 +187,7 @@ MemberDeclarationSyntax RemoveRequiresUnreferencedCodeAttributeIfNeeded(MemberDe
         // If the target type has at least one custom constructor, only generate methods
         foreach (MemberDeclarationSyntax member in memberDeclarations.Where(static member => member is not ConstructorDeclarationSyntax))
         {
-            builder.Add(RemoveRequiresUnreferencedCodeAttributeIfNeeded(member));
+            builder.Add(FixupFilteredMemberDeclaration(member));
         }
 
         return builder.ToImmutable();

CommunityToolkit.Mvvm.SourceGenerators/EmbeddedResources/ObservableRecipient.cs

@@ -66,16 +66,9 @@ public bool IsActive
     }
 
     /// <summary>
-    /// Raised whenever the <see cref="IsActive"/> property is set to <see langword="true"/>.
+    /// Invoked whenever the <see cref="IsActive"/> property is set to <see langword="true"/>.
     /// Use this method to register to messages and do other initialization for this instance.
     /// </summary>
-    /// <remarks>
-    /// The base implementation registers all messages for this recipients that have been declared
-    /// explicitly through the <see cref="global::CommunityToolkit.Mvvm.Messaging.IRecipient{TMessage}"/> interface, using the default channel.
-    /// For more details on how this works, see the <see cref="global::CommunityToolkit.Mvvm.Messaging.IMessengerExtensions.RegisterAll"/> method.
-    /// If you need more fine tuned control, want to register messages individually or just prefer
-    /// the lambda-style syntax for message registration, override this method and register manually.
-    /// </remarks>
     [global::System.Diagnostics.CodeAnalysis.RequiresUnreferencedCode(
         "This method requires the generated CommunityToolkit.Mvvm.Messaging.__Internals.__IMessengerExtensions type not to be removed to use the fast path. " +
         "If this type is removed by the linker, or if the target recipient was created dynamically and was missed by the source generator, a slower fallback " +
@@ -87,15 +80,9 @@ protected virtual void OnActivated()
     }
 
     /// <summary>
-    /// Raised whenever the <see cref="IsActive"/> property is set to <see langword="false"/>.
+    /// Invoked whenever the <see cref="IsActive"/> property is set to <see langword="false"/>.
     /// Use this method to unregister from messages and do general cleanup for this instance.
     /// </summary>
-    /// <remarks>
-    /// The base implementation unregisters all messages for this recipient. It does so by
-    /// invoking <see cref="global::CommunityToolkit.Mvvm.Messaging.IMessenger.UnregisterAll"/>, which removes all registered
-    /// handlers for a given subscriber, regardless of what token was used to register them.
-    /// That is, all registered handlers across all subscription channels will be removed.
-    /// </remarks>
     protected virtual void OnDeactivated()
     {
         Messenger.UnregisterAll(this);

CommunityToolkit.Mvvm/ComponentModel/ObservableRecipient.cs

@@ -81,7 +81,7 @@ public bool IsActive
     }
 
     /// <summary>
-    /// Raised whenever the <see cref="IsActive"/> property is set to <see langword="true"/>.
+    /// Invoked whenever the <see cref="IsActive"/> property is set to <see langword="true"/>.
     /// Use this method to register to messages and do other initialization for this instance.
     /// </summary>
     /// <remarks>
@@ -102,7 +102,7 @@ protected virtual void OnActivated()
     }
 
     /// <summary>
-    /// Raised whenever the <see cref="IsActive"/> property is set to <see langword="false"/>.
+    /// Invoked whenever the <see cref="IsActive"/> property is set to <see langword="false"/>.
     /// Use this method to unregister from messages and do general cleanup for this instance.
     /// </summary>
     /// <remarks>

tests/CommunityToolkit.Mvvm.UnitTests/Test_ObservableRecipientAttribute.cs

@@ -153,4 +153,79 @@ public void Test_ObservableRecipientAttribute_TrimmingAnnoations_OnActivated()
     public abstract partial class TestRecipient : ObservableObject
     {
     }
+
+    [TestMethod]
+    public void Test_ObservableRecipientAttribute_PersonWithCustomOnActivated()
+    {
+        PersonWithCustomOnActivated model = new();
+
+        model.IsActive = true;
+
+        Assert.IsTrue(model.Result);
+    }
+
+    [ObservableRecipient]
+    public partial class PersonWithCustomOnActivated : ObservableObject
+    {
+        public bool Result { get; private set; }
+
+        protected virtual partial void OnActivated()
+        {
+            Result = true;
+        }
+    }
+
+    [TestMethod]
+    public void Test_ObservableRecipientAttribute_PersonWithCustomOnDeactivated()
+    {
+        PersonWithCustomOnDeactivated model = new();
+
+        model.IsActive = true;
+        model.IsActive = false;
+
+        Assert.IsTrue(model.Result);
+    }
+
+    [ObservableRecipient]
+    public partial class PersonWithCustomOnDeactivated : ObservableObject
+    {
+        public bool Result { get; private set; }
+
+        protected virtual partial void OnDeactivated()
+        {
+            Result = true;
+        }
+    }
+
+    [TestMethod]
+    public void Test_ObservableRecipientAttribute_PersonWithCustomOnActivatedAndOnDeactivated()
+    {
+        PersonWithCustomOnActivatedAndOnDeactivated model = new();
+
+        model.IsActive = true;
+
+        Assert.IsTrue(model.OnActivatedResult);
+
+        model.IsActive = false;
+
+        Assert.IsTrue(model.OnDeactivatedResult);
+    }
+
+    [ObservableRecipient]
+    public partial class PersonWithCustomOnActivatedAndOnDeactivated : ObservableObject
+    {
+        public bool OnActivatedResult { get; private set; }
+
+        public bool OnDeactivatedResult { get; private set; }
+
+        protected virtual partial void OnActivated()
+        {
+            OnActivatedResult = true;
+        }
+
+        protected virtual partial void OnDeactivated()
+        {
+            OnDeactivatedResult = true;
+        }
+    }
 }