Enable trimming support in the MVVM Toolkit

Also added linker annotations where needed

CommunityToolkit.Mvvm/Attributes/RequiresUnreferencedCodeAttribute.cs

@@ -0,0 +1,37 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#if !NET6_0_OR_GREATER
+
+namespace System.Diagnostics.CodeAnalysis;
+
+/// <summary>
+/// Indicates that the specified method requires dynamic access to code that is not referenced statically.
+/// </summary>
+[AttributeUsage(AttributeTargets.Method | AttributeTargets.Constructor | AttributeTargets.Class, Inherited = false)]
+[Conditional("DEBUG")]
+internal sealed class RequiresUnreferencedCodeAttribute : Attribute
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="RequiresUnreferencedCodeAttribute"/> class.
+    /// </summary>
+    /// <param name="message">A message that contains information about the usage of unreferenced code.</param>
+    public RequiresUnreferencedCodeAttribute(string message)
+    {
+        Message = message;
+    }
+
+    /// <summary>
+    /// Gets a message that contains information about the usage of unreferenced code.
+    /// </summary>
+    public string Message { get; }
+
+    /// <summary>
+    /// Gets or sets an optional URL that contains more information about the method,
+    /// why it requires unreferenced code, and what options a consumer has to deal with it.
+    /// </summary>
+    public string? Url { get; set; }
+}
+
+#endif

CommunityToolkit.Mvvm/CommunityToolkit.Mvvm.csproj

@@ -33,6 +33,12 @@
     <PackageReference Include="System.ComponentModel.Annotations" Version="5.0.0" />
     <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="6.0.0" />
   </ItemGroup>
+
+  <!-- Enable trimming support on .NET 6 -->
+  <PropertyGroup Condition="'$(TargetFramework)' == 'net6.0'">
+    <EnableTrimAnalyzer>true</EnableTrimAnalyzer>
+    <IsTrimmable>true</IsTrimmable>
+  </PropertyGroup>
     
   <!-- Source generator project reference for packing -->
   <ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">

CommunityToolkit.Mvvm/ComponentModel/ObservableRecipient.cs

@@ -57,6 +57,13 @@ public abstract class ObservableRecipient : ObservableObject
     public bool IsActive
     {
         get => this.isActive;
+
+        [RequiresUnreferencedCode(
+            "When this property is set to true, the OnActivated() method will be invoked, which will register all necessary message handlers for this recipient. " +
+            "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 " +
+            "path using a compiled LINQ expression will be used. This will have more overhead in the first invocation of this method for any given recipient type. " +
+            "Alternatively, OnActivated() can be manually overwritten, and registration can be done individually for each required message for this recipient.")]
         set
         {
             if (SetProperty(ref this.isActive, value, true))
@@ -84,6 +91,11 @@ public abstract class ObservableRecipient : ObservableObject
     /// 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>
+    [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 " +
+        "path using a compiled LINQ expression will be used. This will have more overhead in the first invocation of this method for any given recipient type. " +
+        "Alternatively, OnActivated() can be manually overwritten, and registration can be done individually for each required message for this recipient.")]
     protected virtual void OnActivated()
     {
         Messenger.RegisterAll(this);

CommunityToolkit.Mvvm/ComponentModel/ObservableValidator.cs

@@ -69,6 +69,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// be used to validate all properties, which will reference the current instance
     /// and no additional services or validation properties and settings.
     /// </summary>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected ObservableValidator()
     {
         this.validationContext = new ValidationContext(this);
@@ -80,6 +81,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// be used to validate all properties, which will reference the current instance.
     /// </summary>
     /// <param name="items">A set of key/value pairs to make available to consumers.</param>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected ObservableValidator(IDictionary<object, object?>? items)
     {
         this.validationContext = new ValidationContext(this, items);
@@ -92,6 +94,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// </summary>
     /// <param name="serviceProvider">An <see cref="IServiceProvider"/> instance to make available during validation.</param>
     /// <param name="items">A set of key/value pairs to make available to consumers.</param>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected ObservableValidator(IServiceProvider? serviceProvider, IDictionary<object, object?>? items)
     {
         this.validationContext = new ValidationContext(this, serviceProvider, items);
@@ -141,6 +144,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// are not raised if the current and new value for the target property are the same.
     /// </remarks>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="propertyName"/> is <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool SetProperty<T>([NotNullIfNotNull("newValue")] ref T field, T newValue, bool validate, [CallerMemberName] string propertyName = null!)
     {
         ArgumentNullException.ThrowIfNull(propertyName);
@@ -169,6 +173,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="propertyName">(optional) The name of the property that changed.</param>
     /// <returns><see langword="true"/> if the property was changed, <see langword="false"/> otherwise.</returns>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="comparer"/> or <paramref name="propertyName"/> are <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool SetProperty<T>([NotNullIfNotNull("newValue")] ref T field, T newValue, IEqualityComparer<T> comparer, bool validate, [CallerMemberName] string propertyName = null!)
     {
         ArgumentNullException.ThrowIfNull(comparer);
@@ -205,6 +210,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// are not raised if the current and new value for the target property are the same.
     /// </remarks>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="callback"/> or <paramref name="propertyName"/> are <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool SetProperty<T>(T oldValue, T newValue, Action<T> callback, bool validate, [CallerMemberName] string propertyName = null!)
     {
         ArgumentNullException.ThrowIfNull(callback);
@@ -235,6 +241,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="propertyName">(optional) The name of the property that changed.</param>
     /// <returns><see langword="true"/> if the property was changed, <see langword="false"/> otherwise.</returns>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="comparer"/>, <paramref name="callback"/> or <paramref name="propertyName"/> are <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool SetProperty<T>(T oldValue, T newValue, IEqualityComparer<T> comparer, Action<T> callback, bool validate, [CallerMemberName] string propertyName = null!)
     {
         ArgumentNullException.ThrowIfNull(comparer);
@@ -269,6 +276,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="propertyName">(optional) The name of the property that changed.</param>
     /// <returns><see langword="true"/> if the property was changed, <see langword="false"/> otherwise.</returns>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="model"/>, <paramref name="callback"/> or <paramref name="propertyName"/> are <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool SetProperty<TModel, T>(T oldValue, T newValue, TModel model, Action<TModel, T> callback, bool validate, [CallerMemberName] string propertyName = null!)
         where TModel : class
     {
@@ -306,6 +314,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="propertyName">(optional) The name of the property that changed.</param>
     /// <returns><see langword="true"/> if the property was changed, <see langword="false"/> otherwise.</returns>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="comparer"/>, <paramref name="model"/>, <paramref name="callback"/> or <paramref name="propertyName"/> are <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool SetProperty<TModel, T>(T oldValue, T newValue, IEqualityComparer<T> comparer, TModel model, Action<TModel, T> callback, bool validate, [CallerMemberName] string propertyName = null!)
         where TModel : class
     {
@@ -335,6 +344,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="propertyName">(optional) The name of the property that changed.</param>
     /// <returns>Whether the validation was successful and the property value changed as well.</returns>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="propertyName"/> is <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool TrySetProperty<T>(ref T field, T newValue, out IReadOnlyCollection<ValidationResult> errors, [CallerMemberName] string propertyName = null!)
     {
         ArgumentNullException.ThrowIfNull(propertyName);
@@ -355,6 +365,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="propertyName">(optional) The name of the property that changed.</param>
     /// <returns>Whether the validation was successful and the property value changed as well.</returns>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="comparer"/> or <paramref name="propertyName"/> are <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool TrySetProperty<T>(ref T field, T newValue, IEqualityComparer<T> comparer, out IReadOnlyCollection<ValidationResult> errors, [CallerMemberName] string propertyName = null!)
     {
         ArgumentNullException.ThrowIfNull(comparer);
@@ -376,6 +387,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="propertyName">(optional) The name of the property that changed.</param>
     /// <returns>Whether the validation was successful and the property value changed as well.</returns>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="callback"/> or <paramref name="propertyName"/> are <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool TrySetProperty<T>(T oldValue, T newValue, Action<T> callback, out IReadOnlyCollection<ValidationResult> errors, [CallerMemberName] string propertyName = null!)
     {
         ArgumentNullException.ThrowIfNull(callback);
@@ -398,6 +410,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="propertyName">(optional) The name of the property that changed.</param>
     /// <returns>Whether the validation was successful and the property value changed as well.</returns>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="comparer"/>, <paramref name="callback"/> or <paramref name="propertyName"/> are <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool TrySetProperty<T>(T oldValue, T newValue, IEqualityComparer<T> comparer, Action<T> callback, out IReadOnlyCollection<ValidationResult> errors, [CallerMemberName] string propertyName = null!)
     {
         ArgumentNullException.ThrowIfNull(comparer);
@@ -422,6 +435,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="propertyName">(optional) The name of the property that changed.</param>
     /// <returns>Whether the validation was successful and the property value changed as well.</returns>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="model"/>, <paramref name="callback"/> or <paramref name="propertyName"/> are <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool TrySetProperty<TModel, T>(T oldValue, T newValue, TModel model, Action<TModel, T> callback, out IReadOnlyCollection<ValidationResult> errors, [CallerMemberName] string propertyName = null!)
         where TModel : class
     {
@@ -448,6 +462,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="propertyName">(optional) The name of the property that changed.</param>
     /// <returns>Whether the validation was successful and the property value changed as well.</returns>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="comparer"/>, <paramref name="model"/>, <paramref name="callback"/> or <paramref name="propertyName"/> are <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected bool TrySetProperty<TModel, T>(T oldValue, T newValue, IEqualityComparer<T> comparer, TModel model, Action<TModel, T> callback, out IReadOnlyCollection<ValidationResult> errors, [CallerMemberName] string propertyName = null!)
         where TModel : class
     {
@@ -523,8 +538,14 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// members in the current instance will be ignored. None of the processed properties
     /// will be modified - they will only be used to retrieve their values and validate them.
     /// </remarks>
+    [RequiresUnreferencedCode(
+        "This method requires the generated CommunityToolkit.Mvvm.ComponentModel.__Internals.__ObservableValidatorExtensions 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 " +
+        "path using a compiled LINQ expression will be used. This will have more overhead in the first invocation of this method for any given recipient type. " +
+        "Additionally, due to the usage of validation APIs, the type of the current instance cannot be statically discovered.")]
     protected void ValidateAllProperties()
     {
+#pragma warning disable IL2026
         // Fast path that tries to create a delegate from a generated type-specific method. This
         // is used to make this method more AOT-friendly and faster, as there is no dynamic code.
         static Action<object> GetValidationAction(Type type)
@@ -537,6 +558,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
 
             return GetValidationActionFallback(type);
         }
+#pragma warning restore IL2026
 
         // Fallback method to create the delegate with a compiled LINQ expression
         static Action<object> GetValidationActionFallback(Type type)
@@ -603,6 +625,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="value">The value to test for the specified property.</param>
     /// <param name="propertyName">The name of the property to validate.</param>
     /// <exception cref="ArgumentNullException">Thrown when <paramref name="propertyName"/> is <see langword="null"/>.</exception>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     protected internal void ValidateProperty(object? value, [CallerMemberName] string propertyName = null!)
     {
         ArgumentNullException.ThrowIfNull(propertyName);
@@ -679,6 +702,7 @@ public abstract class ObservableValidator : ObservableObject, INotifyDataErrorIn
     /// <param name="value">The value to test for the specified property.</param>
     /// <param name="propertyName">The name of the property to validate.</param>
     /// <param name="errors">The resulting validation errors, if any.</param>
+    [RequiresUnreferencedCode("The type of the current instance cannot be statically discovered.")]
     private bool TryValidateProperty(object? value, string propertyName, out IReadOnlyCollection<ValidationResult> errors)
     {
         // Add the cached errors list for later use.

CommunityToolkit.Mvvm/ComponentModel/__Internals/__ObservableValidatorHelper.cs

@@ -25,6 +25,8 @@ public static class __ObservableValidatorHelper
     [Obsolete("This method is not intended to be called directly by user code")]
     public static void ValidateProperty(ObservableValidator instance, object? value, string propertyName)
     {
+#pragma warning disable IL2026
         instance.ValidateProperty(value, propertyName);
+#pragma warning restore IL2026
     }
 }

CommunityToolkit.Mvvm/Messaging/IMessengerExtensions.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Reflection;
@@ -85,11 +86,16 @@ public static class IMessengerExtensions
     /// <param name="recipient">The recipient that will receive the messages.</param>
     /// <remarks>See notes for <see cref="RegisterAll{TToken}(IMessenger,object,TToken)"/> for more info.</remarks>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="messenger"/> or <paramref name="recipient"/> are <see langword="null"/>.</exception>
+    [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 " +
+        "path using a compiled LINQ expression will be used. This will have more overhead in the first invocation of this method for any given recipient type.")]
     public static void RegisterAll(this IMessenger messenger, object recipient)
     {
         ArgumentNullException.ThrowIfNull(messenger);
         ArgumentNullException.ThrowIfNull(recipient);
 
+#pragma warning disable IL2026
         // We use this method as a callback for the conditional weak table, which will handle
         // thread-safety for us. This first callback will try to find a generated method for the
         // target recipient type, and just invoke it to get the delegate to cache and use later.
@@ -103,6 +109,7 @@ public static class IMessengerExtensions
 
             return null;
         }
+#pragma warning restore IL2026
 
         // Try to get the cached delegate, if the generatos has run correctly
         Action<IMessenger, object>? registrationAction = DiscoveredRecipients.RegistrationMethods.GetValue(
@@ -134,6 +141,10 @@ public static class IMessengerExtensions
     /// registered directly through any of the other generic extensions for the <see cref="IMessenger"/> interface.
     /// </remarks>
     /// <exception cref="System.ArgumentNullException">Thrown if <paramref name="messenger"/>, <paramref name="recipient"/> or <paramref name="token"/> are <see langword="null"/>.</exception>
+    [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 " +
+        "path using a compiled LINQ expression will be used. This will have more overhead in the first invocation of this method for any given recipient type.")]
     public static void RegisterAll<TToken>(this IMessenger messenger, object recipient, TToken token)
         where TToken : IEquatable<TToken>
     {
@@ -141,6 +152,7 @@ public static class IMessengerExtensions
         ArgumentNullException.ThrowIfNull(recipient);
         ArgumentNullException.For<TToken>.ThrowIfNull(token);
 
+#pragma warning disable IL2026
         // We use this method as a callback for the conditional weak table, which will handle
         // thread-safety for us. This first callback will try to find a generated method for the
         // target recipient type, and just invoke it to get the delegate to cache and use later.
@@ -212,6 +224,7 @@ public static class IMessengerExtensions
 
             return Expression.Lambda<Action<IMessenger, object, TToken>>(body, arg0, arg1, arg2).Compile();
         }
+#pragma warning restore IL2026
 
         // Get or compute the registration method for the current recipient type.
         // As in CommunityToolkit.Diagnostics.TypeExtensions.ToTypeString, we use a lambda