Fix dependency property generator default value emission

Directory.Build.props

@@ -1,37 +1,41 @@
-<Project>
-  <PropertyGroup>
-    <MajorVersion>0</MajorVersion>
-    <MinorVersion>1</MinorVersion>
-
-    <PackageIdPrefix>CommunityToolkit.Labs</PackageIdPrefix>
-    <RepositoryDirectory>$([MSBuild]::EnsureTrailingSlash('$(MSBuildThisFileDirectory)'))</RepositoryDirectory>
-    <ToolingDirectory>$(RepositoryDirectory)tooling</ToolingDirectory>    
-    <EnableNETAnalyzers>true</EnableNETAnalyzers>
-  </PropertyGroup>
-
-  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
-    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
-    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
-    <NoWarn>$(NoWarn);Uno0001</NoWarn>
-
-    <!-- See https://github.com/CommunityToolkit/Labs-Windows/pull/605#issuecomment-2498743676 -->
-    <WarningsNotAsErrors>NU1901;NU1902;NU1903;NU1904;</WarningsNotAsErrors>
-
-    <!-- Labs only: No error for 'Missing XML comment for publicly visible type or member' -->
-    <WarningsNotAsErrors>$(WarningsNotAsErrors);CS1591;CS1574;</WarningsNotAsErrors>
-
-    <!-- See https://github.com/CommunityToolkit/Windows/pull/609#issuecomment-2613505591 -->
-    <WarningsNotAsErrors>$(WarningsNotAsErrors);CS0419;CS1570;</WarningsNotAsErrors>
-  </PropertyGroup>
-
-  <Import Project="Windows.Toolkit.Common.props" />
-
-  <PropertyGroup>
-    <DebugType>Embedded</DebugType>
-    <PackageOutputPath>bin\Package</PackageOutputPath>
-    <AllowedOutputExtensionsInPackageBuildOutputFolder>.pdb</AllowedOutputExtensionsInPackageBuildOutputFolder>
-    <PublishRepositoryUrl>true</PublishRepositoryUrl>
-    <EmbedUntrackedSources>true</EmbedUntrackedSources>
-  </PropertyGroup>
-
-</Project>
+<Project>
+  <PropertyGroup>
+    <MajorVersion>0</MajorVersion>
+    <MinorVersion>1</MinorVersion>
+
+    <PackageIdPrefix>CommunityToolkit.Labs</PackageIdPrefix>
+    <RepositoryDirectory>$([MSBuild]::EnsureTrailingSlash('$(MSBuildThisFileDirectory)'))</RepositoryDirectory>
+    <ToolingDirectory>$(RepositoryDirectory)tooling</ToolingDirectory>    
+    <EnableNETAnalyzers>true</EnableNETAnalyzers>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
+    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <NoWarn>$(NoWarn);Uno0001</NoWarn>
+
+
+    <!-- See https://github.com/CommunityToolkit/Labs-Windows/pull/605#issuecomment-2498743676 -->
+    <WarningsNotAsErrors>NU1901;NU1902;NU1903;NU1904;</WarningsNotAsErrors>
+
+    <!-- Labs only: No error for 'Missing XML comment for publicly visible type or member' -->
+    <WarningsNotAsErrors>$(WarningsNotAsErrors);CS1591;CS1574;</WarningsNotAsErrors>
+
+    <!-- See https://github.com/CommunityToolkit/Windows/pull/609#issuecomment-2613505591 -->
+    <WarningsNotAsErrors>$(WarningsNotAsErrors);CS0419;CS1570;</WarningsNotAsErrors>
+
+    <!-- Don't block Labs builds just because samples are underdeveloped -->
+    <WarningsNotAsErrors>$(WarningsNotAsErrors);TKSMPL0014;TKSMPL0013;</WarningsNotAsErrors>
+  </PropertyGroup>
+
+  <Import Project="Windows.Toolkit.Common.props" />
+
+  <PropertyGroup>
+    <DebugType>Embedded</DebugType>
+    <PackageOutputPath>bin\Package</PackageOutputPath>
+    <AllowedOutputExtensionsInPackageBuildOutputFolder>.pdb</AllowedOutputExtensionsInPackageBuildOutputFolder>
+    <PublishRepositoryUrl>true</PublishRepositoryUrl>
+    <EmbedUntrackedSources>true</EmbedUntrackedSources>
+  </PropertyGroup>
+
+</Project>

ReadMe.md

@@ -30,7 +30,7 @@ Otherwise, you can clone the repo, open the `components` directory, navigate wit
 - [CanvasView](https://github.com/CommunityToolkit/Labs-Windows/blob/main/components/CanvasView/samples/CanvasView.md)
 - [ColorAnalyzer](https://github.com/CommunityToolkit/Labs-Windows/tree/main/components/ColorAnalyzer)
 - [DataTable](https://github.com/CommunityToolkit/Labs-Windows/blob/main/components/DataTable/samples/DataTable.md)
-- [DependencyPropertyGenerator](https://github.com/CommunityToolkit/Labs-Windows/tree/main/components/DependencyPropertyGenerator)
+- [DependencyPropertyGenerator](https://github.com/CommunityToolkit/Labs-Windows/blob/main/components/DependencyPropertyGenerator/samples/DependencyPropertyGenerator.md)
 - [Extensions.DependencyInjection](https://github.com/CommunityToolkit/Labs-Windows/tree/main/components/Extensions.DependencyInjection)
 - [MarkdownTextBlock](https://github.com/CommunityToolkit/Labs-Windows/blob/main/components/MarkdownTextBlock/samples/MarkdownTextBlock.md)
 - [Marquee](https://github.com/CommunityToolkit/Labs-Windows/blob/main/components/Marquee/samples/Marquee.md)

components/DependencyPropertyGenerator/.gitattributes

@@ -7,4 +7,5 @@
 *.cs           text      eol=lf
 *.csproj       text      eol=lf
 *.projitems    text      eol=lf
-*.shprroj      text      eol=lf
+*.shprroj      text      eol=lf
+*.xaml         text      eol=crlf

components/DependencyPropertyGenerator/CommunityToolkit.DependencyPropertyGenerator.SourceGenerators/DependencyPropertyGenerator.Execute.cs

@@ -307,7 +307,7 @@ public static DependencyPropertyDefaultValue GetDefaultValue(
                         // Validate the method has a valid signature as well
                         if (InvalidPropertyDefaultValueCallbackTypeAnalyzer.IsDefaultValueCallbackValid(propertySymbol, methodSymbol))
                         {
-                            return new DependencyPropertyDefaultValue.Callback(methodName);
+                            return new DependencyPropertyDefaultValue.Callback(methodName, RequiresBoxing: !methodSymbol.ReturnType.IsReferenceType);
                         }
                     }
                 }
@@ -690,33 +690,33 @@ static string GetExpressionWithTrailingSpace(Accessibility accessibility)
                     // Shared codegen
                     { DefaultValue: DependencyPropertyDefaultValue.Null or DependencyPropertyDefaultValue.Default(_, true), IsPropertyChangedCallbackImplemented: false, IsSharedPropertyChangedCallbackImplemented: false }
                         => "null",
-                    { DefaultValue: DependencyPropertyDefaultValue.Callback(string methodName), IsPropertyChangedCallbackImplemented: false, IsSharedPropertyChangedCallbackImplemented: false }
+                    { DefaultValue: DependencyPropertyDefaultValue.Callback callback, IsPropertyChangedCallbackImplemented: false, IsSharedPropertyChangedCallbackImplemented: false }
                         => $"""
                         global::{WellKnownTypeNames.PropertyMetadata(propertyInfo.UseWindowsUIXaml)}.Create(
-                            createDefaultValueCallback: new {WellKnownTypeNames.CreateDefaultValueCallback(propertyInfo.UseWindowsUIXaml)}({methodName}))
+                            createDefaultValueCallback: new {WellKnownTypeNames.CreateDefaultValueCallback(propertyInfo.UseWindowsUIXaml)}({callback}))
                         """,
                     { DefaultValue: { } defaultValue, IsPropertyChangedCallbackImplemented: false, IsSharedPropertyChangedCallbackImplemented: false }
                         => $"new global::{WellKnownTypeNames.PropertyMetadata(propertyInfo.UseWindowsUIXaml)}({defaultValue})",
 
                     // Codegen for legacy UWP
                     { IsAdditionalTypesGenerationSupported: false } => propertyInfo switch
                     {
-                        { DefaultValue: DependencyPropertyDefaultValue.Callback(string methodName), IsPropertyChangedCallbackImplemented: true, IsSharedPropertyChangedCallbackImplemented: false }
+                        { DefaultValue: DependencyPropertyDefaultValue.Callback callback, IsPropertyChangedCallbackImplemented: true, IsSharedPropertyChangedCallbackImplemented: false }
                             => $"""
                             global::{WellKnownTypeNames.PropertyMetadata(propertyInfo.UseWindowsUIXaml)}.Create(
-                                 createDefaultValueCallback: new {WellKnownTypeNames.CreateDefaultValueCallback(propertyInfo.UseWindowsUIXaml)}({methodName}),
+                                 createDefaultValueCallback: new {WellKnownTypeNames.CreateDefaultValueCallback(propertyInfo.UseWindowsUIXaml)}({callback}),
                                  propertyChangedCallback: static (d, e) => (({typeQualifiedName})d).On{propertyInfo.PropertyName}PropertyChanged(e))
                             """,
-                        { DefaultValue: DependencyPropertyDefaultValue.Callback(string methodName), IsPropertyChangedCallbackImplemented: false, IsSharedPropertyChangedCallbackImplemented: true }
+                        { DefaultValue: DependencyPropertyDefaultValue.Callback callback, IsPropertyChangedCallbackImplemented: false, IsSharedPropertyChangedCallbackImplemented: true }
                             => $"""
                             global::{WellKnownTypeNames.PropertyMetadata(propertyInfo.UseWindowsUIXaml)}.Create(
-                                createDefaultValueCallback: new {WellKnownTypeNames.CreateDefaultValueCallback(propertyInfo.UseWindowsUIXaml)}({methodName}),
+                                createDefaultValueCallback: new {WellKnownTypeNames.CreateDefaultValueCallback(propertyInfo.UseWindowsUIXaml)}({callback}),
                                 propertyChangedCallback: static (d, e) => (({typeQualifiedName})d).OnPropertyChanged(e))
                             """,
-                        { DefaultValue: DependencyPropertyDefaultValue.Callback(string methodName), IsPropertyChangedCallbackImplemented: true, IsSharedPropertyChangedCallbackImplemented: true }
+                        { DefaultValue: DependencyPropertyDefaultValue.Callback callback, IsPropertyChangedCallbackImplemented: true, IsSharedPropertyChangedCallbackImplemented: true }
                             => $$"""
                             global::{{WellKnownTypeNames.PropertyMetadata(propertyInfo.UseWindowsUIXaml)}}.Create(
-                                createDefaultValueCallback: new {{WellKnownTypeNames.CreateDefaultValueCallback(propertyInfo.UseWindowsUIXaml)}}({{methodName}}),
+                                createDefaultValueCallback: new {{WellKnownTypeNames.CreateDefaultValueCallback(propertyInfo.UseWindowsUIXaml)}}({{callback}}),
                                 propertyChangedCallback: static (d, e) => { (({{typeQualifiedName}})d).On{{propertyInfo.PropertyName}}PropertyChanged(e); (({{typeQualifiedName}})d).OnPropertyChanged(e); })
                             """,
                         { DefaultValue: { } defaultValue, IsPropertyChangedCallbackImplemented: true, IsSharedPropertyChangedCallbackImplemented: false }
@@ -753,10 +753,10 @@ static string GetExpressionWithTrailingSpace(Accessibility accessibility)
                             defaultValue: null,
                             propertyChangedCallback: global::{GeneratorName}.PropertyChangedCallbacks.{propertyInfo.PropertyName}())
                         """,
-                    { DefaultValue: DependencyPropertyDefaultValue.Callback(string methodName) }
+                    { DefaultValue: DependencyPropertyDefaultValue.Callback callback }
                         => $"""
                         global::{WellKnownTypeNames.PropertyMetadata(propertyInfo.UseWindowsUIXaml)}.Create(
-                            createDefaultValueCallback: new {WellKnownTypeNames.CreateDefaultValueCallback(propertyInfo.UseWindowsUIXaml)}({methodName}),
+                            createDefaultValueCallback: new {WellKnownTypeNames.CreateDefaultValueCallback(propertyInfo.UseWindowsUIXaml)}({callback}),
                             propertyChangedCallback: global::{GeneratorName}.PropertyChangedCallbacks.{propertyInfo.PropertyName}())
                         """,
                     { DefaultValue: { } defaultValue } and ({ IsPropertyChangedCallbackImplemented: true } or { IsSharedPropertyChangedCallbackImplemented: true })
@@ -818,8 +818,11 @@ static string GetExpressionWithTrailingSpace(Accessibility accessibility)
                 // We will never have the 'partial' modifier in the set of property modifiers processed above.
                 writer.WriteLine($"partial {propertyInfo.TypeNameWithNullabilityAnnotations} {propertyInfo.PropertyName}");
 
-                using (writer.WriteBlock())
+                writer.WriteLine("{");
+
                 {
+                    writer.IncreaseIndent();
+
                     // We need very different codegen depending on whether local caching is enabled or not
                     if (propertyInfo.IsLocalCachingEnabled)
                     {
@@ -894,13 +897,6 @@ static string GetExpressionWithTrailingSpace(Accessibility accessibility)
                                 """, isMultiline: true);
                         }
 
-                        // If the default value is not what the default field value would be, add an initializer
-                        if (propertyInfo.DefaultValue is not (DependencyPropertyDefaultValue.Null or DependencyPropertyDefaultValue.Default or DependencyPropertyDefaultValue.Callback))
-                        {
-                            writer.Write($" = {propertyInfo.DefaultValue};");
-                        }
-
-                        // Always leave a newline after the end of the property declaration, in either case
                         writer.WriteLine();
                     }
                     else if (propertyInfo.TypeName == "object")
@@ -1010,7 +1006,20 @@ static string GetExpressionWithTrailingSpace(Accessibility accessibility)
                             }
                             """, isMultiline: true);
                     }
+
+                    writer.DecreaseIndent();
                 }
+
+                writer.Write("}");
+
+                // The initializer follows the property's closing brace, not the setter's
+                if (propertyInfo.IsLocalCachingEnabled &&
+                    propertyInfo.DefaultValue is not (DependencyPropertyDefaultValue.Null or DependencyPropertyDefaultValue.Default or DependencyPropertyDefaultValue.Callback))
+                {
+                    writer.Write($" = {propertyInfo.DefaultValue};");
+                }
+
+                writer.WriteLine();
             }
 
             // Next, emit all partial method declarations at the bottom of the file

components/DependencyPropertyGenerator/CommunityToolkit.DependencyPropertyGenerator.SourceGenerators/Models/DependencyPropertyDefaultValue.cs

@@ -90,12 +90,14 @@ public override string ToString()
     /// A <see cref="DependencyPropertyDefaultValue"/> type representing a callback.
     /// </summary>
     /// <param name="MethodName">The name of the callback method to invoke.</param>
-    public sealed record Callback(string MethodName) : DependencyPropertyDefaultValue
+    /// <param name="RequiresBoxing">Whether the callback return value requires a boxing conversion to <see cref="object"/>.</param>
+    public sealed record Callback(string MethodName, bool RequiresBoxing) : DependencyPropertyDefaultValue
     {
         /// <inheritdoc/>
         public override string ToString()
         {
-            return MethodName;
+            // Method-group conversions cannot box return values, including unconstrained type parameters
+            return RequiresBoxing ? $"static () => {MethodName}()" : MethodName;
         }
     }
 }

components/DependencyPropertyGenerator/CommunityToolkit.DependencyPropertyGenerator.Tests/Helpers/CSharpGeneratorTest{TGenerator}.cs

@@ -11,6 +11,7 @@
 using CommunityToolkit.WinUI;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.Emit;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Windows.Foundation;
 using Windows.UI.ViewManagement;
@@ -55,6 +56,7 @@ public static void VerifyDiagnostics(string source, params string[] diagnosticsI
     /// <param name="source">The input source to process.</param>
     /// <param name="result">The expected source to be generated.</param>
     /// <param name="languageVersion">The language version to use to run the test.</param>
+    /// <remarks>This also supports invalid inputs. Use <see cref="VerifyCompiles"/> to validate compilation.</remarks>
     public static void VerifySources(string source, (string Filename, string Source) result, LanguageVersion languageVersion = LanguageVersion.CSharp13)
     {
         RunGenerator(source, out Compilation compilation, out ImmutableArray<Diagnostic> diagnostics, languageVersion);
@@ -70,6 +72,27 @@ public static void VerifySources(string source, (string Filename, string Source)
         Assert.AreEqual(expectedText, actualText);
     }
 
+    /// <summary>
+    /// Verifies that the resulting sources produced by a source generator can be emitted.
+    /// </summary>
+    /// <param name="source">The input source to process.</param>
+    /// <param name="languageVersion">The language version to use to run the test.</param>
+    /// <returns>The resulting compilation, for further assertions on the generated sources.</returns>
+    public static Compilation VerifyCompiles(string source, LanguageVersion languageVersion = LanguageVersion.CSharp13)
+    {
+        RunGenerator(source, out Compilation compilation, out ImmutableArray<Diagnostic> diagnostics, languageVersion);
+
+        CollectionAssert.AreEquivalent(Array.Empty<Diagnostic>(), diagnostics);
+
+        using MemoryStream stream = new();
+
+        EmitResult result = compilation.Emit(stream);
+
+        Assert.IsTrue(result.Success, $"Failed to emit generated sources:{Environment.NewLine}{string.Join(Environment.NewLine, result.Diagnostics)}");
+
+        return compilation;
+    }
+
     /// <summary>
     /// Verifies the incremental generator steps for a given source generator.
     /// </summary>