Skip MVVMTK0041 when properties are not partial

Author: Sergio0694

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

@@ -7,6 +7,8 @@
 using System.Collections.Immutable;
 using CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
 using static CommunityToolkit.Mvvm.SourceGenerators.Diagnostics.DiagnosticDescriptors;
 
@@ -44,11 +46,25 @@ public override void Initialize(AnalysisContext context)
             context.RegisterSymbolAction(context =>
             {
                 // We only want to target partial property definitions (also include non-partial ones for diagnostics)
-                if (context.Symbol is not IPropertySymbol { PartialDefinitionPart: null })
+                if (context.Symbol is not IPropertySymbol { PartialDefinitionPart: null } partialProperty)
                 {
                     return;
                 }
 
+                // Make sure to skip the warning if the property is not actually partial
+                if (partialProperty.DeclaringSyntaxReferences is [var syntaxReference])
+                {
+                    // Make sure we can find the syntax node, and that it's a property declaration
+                    if (syntaxReference.GetSyntax(context.CancellationToken) is PropertyDeclarationSyntax propertyDeclarationSyntax)
+                    {
+                        // If the property is not partial, ignore it, as we'll already have a warning from the other analyzer here
+                        if (!propertyDeclarationSyntax.Modifiers.Any(SyntaxKind.PartialKeyword))
+                        {
+                            return;
+                        }
+                    }
+                }
+
                 // If the property is using [ObservableProperty], emit the diagnostic
                 if (context.Symbol.TryGetAttributeWithType(observablePropertySymbol, out AttributeData? observablePropertyAttribute))
                 {

tests/CommunityToolkit.Mvvm.SourceGenerators.Roslyn4110.UnitTests/Test_SourceGeneratorsDiagnostics.cs

@@ -5,14 +5,15 @@
 using System.Threading.Tasks;
 using CommunityToolkit.Mvvm.SourceGenerators.UnitTests.Helpers;
 using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.Testing;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
 namespace CommunityToolkit.Mvvm.SourceGenerators.UnitTests;
 
 partial class Test_SourceGeneratorsDiagnostics
 {
     [TestMethod]
-    public async Task RequireCSharpLanguageVersionPreviewAnalyzer_LanguageVersionIsNotPreview_Warns()
+    public async Task RequireCSharpLanguageVersionPreviewAnalyzer_LanguageVersionIsNotPreview_DoesnNotWarn()
     {
         const string source = """
             using CommunityToolkit.Mvvm.ComponentModel;
@@ -21,7 +22,7 @@ namespace MyApp
             {
                 public partial class SampleViewModel : ObservableObject
                 {            
-                    [{|MVVMTK0041:ObservableProperty|}]            
+                    [ObservableProperty]            
                     public string Name { get; set; }
                 }
             }
@@ -30,6 +31,32 @@ public partial class SampleViewModel : ObservableObject
         await VerifyAnalyzerDiagnosticsAndSuccessfulGeneration<RequiresCSharpLanguageVersionPreviewAnalyzer>(source, LanguageVersion.CSharp12);
     }
 
+    [TestMethod]
+    public async Task RequireCSharpLanguageVersionPreviewAnalyzer_LanguageVersionIsNotPreview_Partial_Warns()
+    {
+        const string source = """
+            using CommunityToolkit.Mvvm.ComponentModel;
+            
+            namespace MyApp
+            {
+                public partial class SampleViewModel : ObservableObject
+                {            
+                    [{|MVVMTK0041:ObservableProperty|}]            
+                    public partial string Name { get; set; }
+                }
+            }
+            """;
+
+        await CSharpAnalyzerWithLanguageVersionTest<RequiresCSharpLanguageVersionPreviewAnalyzer>.VerifyAnalyzerAsync(
+            source,
+            LanguageVersion.CSharp12,
+
+            // /0/Test0.cs(8,31): error CS8703: The modifier 'partial' is not valid for this item in C# 12.0. Please use language version 'preview' or greater.
+            DiagnosticResult.CompilerError("CS8703").WithSpan(8, 31, 8, 35).WithArguments("partial", "12.0", "preview"),
+            // /0/Test0.cs(8,31): error CS9248: Partial property 'SampleViewModel.Name' must have an implementation part.
+            DiagnosticResult.CompilerError("CS9248").WithSpan(8, 31, 8, 35).WithArguments("MyApp.SampleViewModel.Name"));
+    }
+
     [TestMethod]
     public async Task RequireCSharpLanguageVersionPreviewAnalyzer_LanguageVersionIsPreview_DoesNotWarn()
     {
@@ -49,6 +76,30 @@ public partial class SampleViewModel : ObservableObject
         await VerifyAnalyzerDiagnosticsAndSuccessfulGeneration<RequiresCSharpLanguageVersionPreviewAnalyzer>(source, languageVersion: LanguageVersion.Preview);
     }
 
+    [TestMethod]
+    public async Task RequireCSharpLanguageVersionPreviewAnalyzer_LanguageVersionIsPreview_Partial_DoesNotWarn()
+    {
+        const string source = """
+            using CommunityToolkit.Mvvm.ComponentModel;
+            
+            namespace MyApp
+            {
+                public partial class SampleViewModel : ObservableObject
+                {            
+                    [ObservableProperty]            
+                    public partial string Name { get; set; }
+                }
+            }
+            """;
+
+        await CSharpAnalyzerWithLanguageVersionTest<RequiresCSharpLanguageVersionPreviewAnalyzer>.VerifyAnalyzerAsync(
+            source,
+            LanguageVersion.Preview,
+
+            // /0/Test0.cs(8,31): error CS9248: Partial property 'SampleViewModel.Name' must have an implementation part.
+            DiagnosticResult.CompilerError("CS9248").WithSpan(8, 31, 8, 35).WithArguments("MyApp.SampleViewModel.Name"));
+    }
+
     [TestMethod]
     public async Task UseObservablePropertyOnPartialPropertyAnalyzer_LanguageVersionIsNotPreview_DoesNotWarn()
     {