Fix C# language version checks for [ObservableProperty]

dotnet.slnx

@@ -1,7 +1,4 @@
 <Solution>
-  <Configurations>
-    <Platform Name="Any CPU" />
-  </Configurations>
   <Folder Name="/Solution Items/">
     <File Path=".editorconfig" />
     <File Path=".gitattributes" />
@@ -40,9 +37,11 @@
     <Project Path="tests/CommunityToolkit.Mvvm.Roslyn4001.UnitTests/CommunityToolkit.Mvvm.Roslyn4001.UnitTests.csproj" />
     <Project Path="tests/CommunityToolkit.Mvvm.Roslyn4031.UnitTests/CommunityToolkit.Mvvm.Roslyn4031.UnitTests.csproj" />
     <Project Path="tests/CommunityToolkit.Mvvm.Roslyn4120.UnitTests/CommunityToolkit.Mvvm.Roslyn4120.UnitTests.csproj" />
+    <Project Path="tests/CommunityToolkit.Mvvm.Roslyn5000.UnitTests/CommunityToolkit.Mvvm.Roslyn5000.UnitTests.csproj" />
     <Project Path="tests/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4001.UnitTests/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4001.UnitTests.csproj" />
     <Project Path="tests/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4031.UnitTests/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4031.UnitTests.csproj" />
     <Project Path="tests/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4120.UnitTests/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4120.UnitTests.csproj" />
+    <Project Path="tests/CommunityToolkit.Mvvm.SourceGenerators.Roslyn5000.UnitTests/CommunityToolkit.Mvvm.SourceGenerators.Roslyn5000.UnitTests.csproj" />
     <Project Path="tests/CommunityToolkit.Mvvm.SourceGenerators.UnitTests/CommunityToolkit.Mvvm.SourceGenerators.UnitTests.shproj" />
     <Project Path="tests/CommunityToolkit.Mvvm.UnitTests/CommunityToolkit.Mvvm.UnitTests.shproj" />
   </Folder>
@@ -58,6 +57,7 @@
   <Project Path="src/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4001/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4001.csproj" />
   <Project Path="src/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4031/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4031.csproj" />
   <Project Path="src/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4120/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4120.csproj" />
+  <Project Path="src/CommunityToolkit.Mvvm.SourceGenerators.Roslyn5000/CommunityToolkit.Mvvm.SourceGenerators.Roslyn5000.csproj" />
   <Project Path="src/CommunityToolkit.Mvvm.SourceGenerators/CommunityToolkit.Mvvm.SourceGenerators.shproj" />
   <Project Path="src/CommunityToolkit.Mvvm/CommunityToolkit.Mvvm.csproj" />
 </Solution>

src/CommunityToolkit.Mvvm.SourceGenerators.Roslyn5000/CommunityToolkit.Mvvm.SourceGenerators.Roslyn5000.csproj

@@ -0,0 +1,6 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <Import Project="..\CommunityToolkit.Mvvm.SourceGenerators\CommunityToolkit.Mvvm.SourceGenerators.props" />
+  <Import Project="..\CommunityToolkit.Mvvm.SourceGenerators\CommunityToolkit.Mvvm.SourceGenerators.projitems" Label="Shared" />
+
+</Project>

src/CommunityToolkit.Mvvm.SourceGenerators/CommunityToolkit.Mvvm.SourceGenerators.projitems

@@ -57,7 +57,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\FieldWithOrphanedDependentObservablePropertyAttributesAnalyzer.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\FieldReferenceForObservablePropertyFieldAnalyzer.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\UnsupportedRoslynVersionForPartialPropertyAnalyzer.cs" />
-    <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\RequiresCSharpLanguageVersionPreviewAnalyzer.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\RequiresCSharpLanguageVersion14OrPreviewAnalyzer.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\InvalidPropertyLevelObservablePropertyAttributeAnalyzer.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\UseObservablePropertyOnPartialPropertyAnalyzer.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Diagnostics\Analyzers\UnsupportedCSharpLanguageVersionAnalyzer.cs" />

src/CommunityToolkit.Mvvm.SourceGenerators/CommunityToolkit.Mvvm.SourceGenerators.props

@@ -41,9 +41,13 @@
     <!-- Also define "ROSLYN_<MAJOR>_<MINOR>_OR_GREATER" build constants, so the generator code can multi-target whenever needed and add any required polyfills -->
     <DefineConstants Condition="$([MSBuild]::VersionGreaterThanOrEquals($(MvvmToolkitSourceGeneratorRoslynVersion), 4.3.1))">$(DefineConstants);ROSLYN_4_3_1_OR_GREATER</DefineConstants>
     <DefineConstants Condition="$([MSBuild]::VersionGreaterThanOrEquals($(MvvmToolkitSourceGeneratorRoslynVersion), 4.12.0))">$(DefineConstants);ROSLYN_4_12_0_OR_GREATER</DefineConstants>
+    <DefineConstants Condition="$([MSBuild]::VersionGreaterThanOrEquals($(MvvmToolkitSourceGeneratorRoslynVersion), 5.0.0))">$(DefineConstants);ROSLYN_5_0_0_OR_GREATER</DefineConstants>
 
     <!-- Disable the removed rules analyzer for older Roslyn versions (as we might not support all diagnostics) -->
-    <NoWarn Condition="$([MSBuild]::VersionLessThan($(MvvmToolkitSourceGeneratorRoslynVersion), 4.12.0))">$(NoWarn);RS2003</NoWarn>
+    <NoWarn Condition="$([MSBuild]::VersionLessThan($(MvvmToolkitSourceGeneratorRoslynVersion), 5.0.0))">$(NoWarn);RS2003</NoWarn>
+
+    <!-- Temporary workaround before GA -->
+    <MvvmToolkitSourceGeneratorRoslynVersion Condition="$([MSBuild]::VersionEquals($(MvvmToolkitSourceGeneratorRoslynVersion), 5.0.0))">5.0.0-2.final</MvvmToolkitSourceGeneratorRoslynVersion>
   </PropertyGroup>
 
   <ItemGroup>

src/CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/ObservablePropertyGenerator.Execute.cs

@@ -80,11 +80,18 @@ public static bool IsCandidateValidForCompilation(MemberDeclarationSyntax node,
                 return false;
             }
 
-            // If the target is a property, we only support using C# preview.
-            // This is because the generator is relying on the 'field' keyword.
-            if (node is PropertyDeclarationSyntax && !semanticModel.Compilation.IsLanguageVersionPreview())
-            {
+            // If the target is a property, we must either be using C# preview, or C# 14 or above. When we're using
+            // an older version of Roslyn, we know properties will never be supported anyway, so we have nothing to
+            // check. When we add Roslyn 18.0 support, we can also update this check to check for at least C# 14.
+            if (node is PropertyDeclarationSyntax)
+            {
+#if ROSLYN_5_0_0_OR_GREATER
+                return semanticModel.Compilation.HasLanguageVersionAtLeastEqualTo(LanguageVersion.CSharp14);
+#elif ROSLYN_4_12_0_OR_GREATER
+                return semanticModel.Compilation.IsLanguageVersionPreview();
+#else
                 return false;
+#endif
             }
 
             // All other cases are supported, the syntax filter is already validating that

src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/Analyzers/RequiresCSharpLanguageVersionPreviewAnalyzer.cs → src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/Analyzers/RequiresCSharpLanguageVersion14OrPreviewAnalyzer.cs

@@ -15,13 +15,13 @@
 namespace CommunityToolkit.Mvvm.SourceGenerators;
 
 /// <summary>
-/// A diagnostic analyzer that generates errors when a property using <c>[ObservableProperty]</c> on a partial property is in a project with the C# language version not set to preview.
+/// A diagnostic analyzer that generates errors when a property using <c>[ObservableProperty]</c> on a partial property is in a project with the C# language version not set to 14.0 or 'preview'.
 /// </summary>
 [DiagnosticAnalyzer(LanguageNames.CSharp)]
-public sealed class RequiresCSharpLanguageVersionPreviewAnalyzer : DiagnosticAnalyzer
+public sealed class RequiresCSharpLanguageVersion14OrPreviewAnalyzer : DiagnosticAnalyzer
 {
     /// <inheritdoc/>
-    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = [CSharpLanguageVersionIsNotPreviewForObservableProperty];
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = [CSharpLanguageVersionIsNot14OrPreviewForObservableProperty];
 
     /// <inheritdoc/>
     public override void Initialize(AnalysisContext context)
@@ -31,8 +31,12 @@ public override void Initialize(AnalysisContext context)
 
         context.RegisterCompilationStartAction(static context =>
         {
-            // If the language version is set to preview, we'll never emit diagnostics
+            // If the language version is set to preview or if we are set to at least C# 14.0, we'll never emit diagnostics
+#if ROSLYN_5_0_0_OR_GREATER
+            if (context.Compilation.HasLanguageVersionAtLeastEqualTo(LanguageVersion.CSharp14))
+#else
             if (context.Compilation.IsLanguageVersionPreview())
+#endif
             {
                 return;
             }
@@ -69,7 +73,7 @@ public override void Initialize(AnalysisContext context)
                 if (context.Symbol.TryGetAttributeWithType(observablePropertySymbol, out AttributeData? observablePropertyAttribute))
                 {
                     context.ReportDiagnostic(Diagnostic.Create(
-                        CSharpLanguageVersionIsNotPreviewForObservableProperty,
+                        CSharpLanguageVersionIsNot14OrPreviewForObservableProperty,
                         observablePropertyAttribute.GetLocation(),
                         context.Symbol));
                 }

src/CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/DiagnosticDescriptors.cs

@@ -691,17 +691,17 @@ internal static class DiagnosticDescriptors
     /// <summary>
     /// Gets a <see cref="DiagnosticDescriptor"/> for the C# language version not being sufficient for <c>[ObservableProperty]</c> on partial properties.
     /// <para>
-    /// Format: <c>"Using [ObservableProperty] on partial properties requires the C# language version to be set to 'preview', as support for the 'field' keyword is needed by the source generators to emit valid code (add <LangVersion>preview</LangVersion> to your .csproj/.props file)"</c>.
+    /// Format: <c>"Using [ObservableProperty] on partial properties requires the C# language version to be set to at least 14.0 or 'preview', as support for the 'field' keyword is needed by the source generators to emit valid code (add <LangVersion>14.0</LangVersion> or <LangVersion>preview</LangVersion> to your .csproj/.props file)"</c>.
     /// </para>
     /// </summary>
-    public static readonly DiagnosticDescriptor CSharpLanguageVersionIsNotPreviewForObservableProperty = new DiagnosticDescriptor(
+    public static readonly DiagnosticDescriptor CSharpLanguageVersionIsNot14OrPreviewForObservableProperty = new DiagnosticDescriptor(
         id: "MVVMTK0041",
-        title: "C# language version is not 'preview'",
-        messageFormat: """Using [ObservableProperty] on partial properties requires the C# language version to be set to 'preview', as support for the 'field' keyword is needed by the source generators to emit valid code (add <LangVersion>preview</LangVersion> to your .csproj/.props file)""",
+        title: "C# language version is not at least 14.0 or 'preview'",
+        messageFormat: """Using [ObservableProperty] on partial properties requires the C# language version to be set to at least 14.0 or 'preview', as support for the 'field' keyword is needed by the source generators to emit valid code (add <LangVersion>14.0</LangVersion> or <LangVersion>preview</LangVersion> to your .csproj/.props file)""",
         category: typeof(ObservablePropertyGenerator).FullName,
         defaultSeverity: DiagnosticSeverity.Error,
         isEnabledByDefault: true,
-        description: "The C# language version must be set to 'preview' when using [ObservableProperty] on partial properties for the source generators to emit valid code (the <LangVersion>preview</LangVersion> option must be set in the .csproj/.props file).",
+        description: "The C# language version must be set to at least 14.0 or 'preview' when using [ObservableProperty] on partial properties for the source generators to emit valid code (the <LangVersion>14.0</LangVersion> or <LangVersion>preview</LangVersion> option must be set in the .csproj/.props file).",
         helpLinkUri: "https://aka.ms/mvvmtoolkit/errors/mvvmtk0041");
 
     /// <summary>

src/CommunityToolkit.Mvvm.SourceGenerators/Extensions/CompilationExtensions.cs

@@ -27,6 +27,17 @@ public static bool HasLanguageVersionAtLeastEqualTo(this Compilation compilation
         return ((CSharpCompilation)compilation).LanguageVersion >= languageVersion;
     }
 
+    /// <summary>
+    /// Checks whether a given compilation (assumed to be for C#) is using a language version greater than a specified one.
+    /// </summary>
+    /// <param name="compilation">The <see cref="Compilation"/> to consider for analysis.</param>
+    /// <param name="languageVersion">The minimum language version to check.</param>
+    /// <returns>Whether <paramref name="compilation"/> is using a language version greater than the specified one.</returns>
+    public static bool HasLanguageVersionGreaterThan(this Compilation compilation, LanguageVersion languageVersion)
+    {
+        return ((CSharpCompilation)compilation).LanguageVersion > languageVersion;
+    }
+
     /// <summary>
     /// Checks whether a given compilation (assumed to be for C#) is using the preview language version.
     /// </summary>

src/CommunityToolkit.Mvvm.SourceGenerators/Extensions/DiagnosticsExtensions.cs

@@ -12,7 +12,7 @@
 namespace CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 
 /// <summary>
-/// Extension methods for <see cref="GeneratorExecutionContext"/>, specifically for reporting diagnostics.
+/// Extension methods for working with diagnostics from incremental generator pipelines.
 /// </summary>
 internal static class DiagnosticsExtensions
 {

src/CommunityToolkit.Mvvm/CommunityToolkit.Mvvm.csproj

@@ -69,6 +69,7 @@
     <ProjectReference Include="..\CommunityToolkit.Mvvm.SourceGenerators.Roslyn4001\CommunityToolkit.Mvvm.SourceGenerators.Roslyn4001.csproj" ReferenceOutputAssembly="false" />
     <ProjectReference Include="..\CommunityToolkit.Mvvm.SourceGenerators.Roslyn4031\CommunityToolkit.Mvvm.SourceGenerators.Roslyn4031.csproj" ReferenceOutputAssembly="false" />
     <ProjectReference Include="..\CommunityToolkit.Mvvm.SourceGenerators.Roslyn4120\CommunityToolkit.Mvvm.SourceGenerators.Roslyn4120.csproj" ReferenceOutputAssembly="false" />
+    <ProjectReference Include="..\CommunityToolkit.Mvvm.SourceGenerators.Roslyn5000\CommunityToolkit.Mvvm.SourceGenerators.Roslyn5000.csproj" ReferenceOutputAssembly="false" />
     <ProjectReference Include="..\CommunityToolkit.Mvvm.CodeFixers.Roslyn4001\CommunityToolkit.Mvvm.CodeFixers.Roslyn4001.csproj" ReferenceOutputAssembly="false" />
     <ProjectReference Include="..\CommunityToolkit.Mvvm.CodeFixers.Roslyn4120\CommunityToolkit.Mvvm.CodeFixers.Roslyn4120.csproj" ReferenceOutputAssembly="false" />
   </ItemGroup>
@@ -123,9 +124,11 @@
     <None Include="..\CommunityToolkit.Mvvm.SourceGenerators.Roslyn4001\bin\$(Configuration)\netstandard2.0\CommunityToolkit.Mvvm.SourceGenerators.dll" PackagePath="analyzers\dotnet\roslyn4.0\cs" Pack="true" Visible="false" />
     <None Include="..\CommunityToolkit.Mvvm.SourceGenerators.Roslyn4031\bin\$(Configuration)\netstandard2.0\CommunityToolkit.Mvvm.SourceGenerators.dll" PackagePath="analyzers\dotnet\roslyn4.3\cs" Pack="true" Visible="false" />
     <None Include="..\CommunityToolkit.Mvvm.SourceGenerators.Roslyn4120\bin\$(Configuration)\netstandard2.0\CommunityToolkit.Mvvm.SourceGenerators.dll" PackagePath="analyzers\dotnet\roslyn4.12\cs" Pack="true" Visible="false" />
+    <None Include="..\CommunityToolkit.Mvvm.SourceGenerators.Roslyn4120\bin\$(Configuration)\netstandard2.0\CommunityToolkit.Mvvm.SourceGenerators.dll" PackagePath="analyzers\dotnet\roslyn5.0\cs" Pack="true" Visible="false" />
     <None Include="..\CommunityToolkit.Mvvm.CodeFixers.Roslyn4001\bin\$(Configuration)\netstandard2.0\CommunityToolkit.Mvvm.CodeFixers.dll" PackagePath="analyzers\dotnet\roslyn4.0\cs" Pack="true" Visible="false" />
     <None Include="..\CommunityToolkit.Mvvm.CodeFixers.Roslyn4001\bin\$(Configuration)\netstandard2.0\CommunityToolkit.Mvvm.CodeFixers.dll" PackagePath="analyzers\dotnet\roslyn4.3\cs" Pack="true" Visible="false" />
     <None Include="..\CommunityToolkit.Mvvm.CodeFixers.Roslyn4120\bin\$(Configuration)\netstandard2.0\CommunityToolkit.Mvvm.CodeFixers.dll" PackagePath="analyzers\dotnet\roslyn4.12\cs" Pack="true" Visible="false" />
+    <None Include="..\CommunityToolkit.Mvvm.CodeFixers.Roslyn4120\bin\$(Configuration)\netstandard2.0\CommunityToolkit.Mvvm.CodeFixers.dll" PackagePath="analyzers\dotnet\roslyn5.0\cs" Pack="true" Visible="false" />
   </ItemGroup>
 
 </Project>

tests/CommunityToolkit.Mvvm.Roslyn5000.UnitTests/CommunityToolkit.Mvvm.Roslyn5000.UnitTests.csproj

@@ -0,0 +1,35 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFrameworks>net472;net8.0;net9.0</TargetFrameworks>
+    <LangVersion>preview</LangVersion>
+    <SuppressTfmSupportBuildWarnings>true</SuppressTfmSupportBuildWarnings>
+    <DefineConstants>$(DefineConstants);ROSLYN_4_12_0_OR_GREATER;ROSLYN_5_0_0_OR_GREATER</DefineConstants>
+
+    <!-- We're intentionally also using '[ObservableProperty]' on some fields, for testing -->
+    <NoWarn>$(NoWarn);MVVMTK0042</NoWarn>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="..\CommunityToolkit.Mvvm.Roslyn4120.UnitTests\Test_ObservablePropertyAttribute_PartialProperties.cs" Link="Test_ObservablePropertyAttribute_PartialProperties.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Dbs.Signed3.Nito.AsyncEx.Context" Version="5.0.0" />
+    <PackageReference Include="MSTest.TestAdapter" Version="4.0.1" />
+    <PackageReference Include="MSTest.TestFramework" Version="4.0.1" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.0" />
+    <PackageReference Include="System.Reactive" Version="6.1.0" />
+    <PackageReference Include="System.Text.Json" Version="9.0.10" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\CommunityToolkit.Mvvm.ExternalAssembly.Roslyn4031\CommunityToolkit.Mvvm.ExternalAssembly.Roslyn4031.csproj" />
+    <ProjectReference Include="..\..\src\CommunityToolkit.Mvvm\CommunityToolkit.Mvvm.csproj" />
+    <ProjectReference Include="..\..\src\CommunityToolkit.Mvvm.SourceGenerators.Roslyn5000\CommunityToolkit.Mvvm.SourceGenerators.Roslyn5000.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" PrivateAssets="contentfiles;build" />
+    <ProjectReference Include="..\..\src\CommunityToolkit.Mvvm.CodeFixers.Roslyn4120\CommunityToolkit.Mvvm.CodeFixers.Roslyn4120.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" PrivateAssets="contentfiles;build" />
+  </ItemGroup>
+
+  <Import Project="..\CommunityToolkit.Mvvm.UnitTests\CommunityToolkit.Mvvm.UnitTests.projitems" Label="Shared" />
+
+</Project>