Merge pull request CommunityToolkit#433 from CommunityToolkit/dev/lan…

…guage-filter-analyzer

Move language diagnostics to diagnostic analyzers

CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/ObservablePropertyGenerator.cs

@@ -12,7 +12,6 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
-using static CommunityToolkit.Mvvm.SourceGenerators.Diagnostics.DiagnosticDescriptors;
 
 namespace CommunityToolkit.Mvvm.SourceGenerators;
 
@@ -30,8 +29,17 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             context.SyntaxProvider
             .CreateSyntaxProvider(
                 static (node, _) => node is FieldDeclarationSyntax { Parent: ClassDeclarationSyntax or RecordDeclarationSyntax, AttributeLists.Count: > 0 },
-                static (context, _) => ((FieldDeclarationSyntax)context.Node).Declaration.Variables.Select(v => (IFieldSymbol)context.SemanticModel.GetDeclaredSymbol(v)!))
-            .SelectMany(static (item, _) => item);
+                static (context, _) =>
+                {
+                    if (!context.SemanticModel.Compilation.HasLanguageVersionAtLeastEqualTo(LanguageVersion.CSharp8))
+                    {
+                        return default;
+                    }
+
+                    return ((FieldDeclarationSyntax)context.Node).Declaration.Variables.Select(v => (IFieldSymbol)context.SemanticModel.GetDeclaredSymbol(v)!);
+                })
+            .Where(static items => items is not null)
+            .SelectMany(static (item, _) => item!)!;
 
         // Filter the fields using [ObservableProperty]
         IncrementalValuesProvider<IFieldSymbol> fieldSymbolsWithAttribute =
@@ -52,9 +60,6 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
         // Output the diagnostics
         context.ReportDiagnostics(fieldSymbolsWithOrphanedDependentAttributeWithErrors);
 
-        // Filter by language version
-        context.FilterWithLanguageVersion(ref fieldSymbolsWithAttribute, LanguageVersion.CSharp8, UnsupportedCSharpLanguageVersionError);
-
         // Gather info for all annotated fields
         IncrementalValuesProvider<(HierarchyInfo Hierarchy, Result<PropertyInfo?> Info)> propertyInfoWithErrors =
             fieldSymbolsWithAttribute

CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/ObservableValidatorValidateAllPropertiesGenerator.cs

@@ -28,7 +28,15 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             context.SyntaxProvider
             .CreateSyntaxProvider(
                 static (node, _) => node is ClassDeclarationSyntax,
-                static (context, _) => (context.Node, Symbol: (INamedTypeSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!))
+                static (context, _) =>
+                {
+                    if (!context.SemanticModel.Compilation.HasLanguageVersionAtLeastEqualTo(LanguageVersion.CSharp8))
+                    {
+                        return default;
+                    }
+
+                    return (context.Node, Symbol: (INamedTypeSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!);
+                })
             .Where(static item => item.Symbol is { IsAbstract: false, IsGenericType: false } && item.Node.IsFirstSyntaxDeclarationForSymbol(item.Symbol))
             .Select(static (item, _) => item.Symbol);
 

CommunityToolkit.Mvvm.SourceGenerators/ComponentModel/TransitiveMembersGenerator.cs

@@ -75,7 +75,16 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             context.SyntaxProvider
             .CreateSyntaxProvider(
                 static (node, _) => node is ClassDeclarationSyntax { AttributeLists.Count: > 0 },
-                static (context, _) => (INamedTypeSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!);
+                static (context, _) =>
+                {
+                    if (!context.SemanticModel.Compilation.HasLanguageVersionAtLeastEqualTo(LanguageVersion.CSharp8))
+                    {
+                        return default;
+                    }
+
+                    return (INamedTypeSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!;
+                })
+            .Where(static item => item is not null)!;
 
         // Filter the types with the target attribute
         IncrementalValuesProvider<(INamedTypeSymbol Symbol, AttributeData AttributeData)> typeSymbolsWithAttributeData =
@@ -88,9 +97,6 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
         // Transform the input data
         IncrementalValuesProvider<(INamedTypeSymbol Symbol, TInfo Info)> typeSymbolsWithInfo = GetInfo(context, typeSymbolsWithAttributeData);
 
-        // Filter by language version
-        context.FilterWithLanguageVersion(ref typeSymbolsWithInfo, LanguageVersion.CSharp8, UnsupportedCSharpLanguageVersionError);
-
         // Gather all generation info, and any diagnostics
         IncrementalValuesProvider<Result<(HierarchyInfo Hierarchy, bool IsSealed, TInfo Info)>> generationInfoWithErrors =
             typeSymbolsWithInfo.Select((item, _) =>

CommunityToolkit.Mvvm.SourceGenerators/Diagnostics/Analyzers/UnsupportedCSharpLanguageVersionAnalyzer.cs

@@ -0,0 +1,93 @@
+// 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.
+
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using CommunityToolkit.Mvvm.SourceGenerators.Extensions;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.Diagnostics;
+using static CommunityToolkit.Mvvm.SourceGenerators.Diagnostics.DiagnosticDescriptors;
+
+namespace CommunityToolkit.Mvvm.SourceGenerators;
+
+/// <summary>
+/// A diagnostic analyzer that generates an error whenever a source-generator attribute is used with not high enough C# version enabled.
+/// </summary>
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class UnsupportedCSharpLanguageVersionAnalyzer : DiagnosticAnalyzer
+{
+    /// <summary>
+    /// The mapping of target attributes that will trigger the analyzer.
+    /// </summary>
+    private static readonly ImmutableDictionary<string, string> GeneratorAttributeNamesToFullyQualifiedNamesMap = ImmutableDictionary.CreateRange(new[]
+    {
+        new KeyValuePair<string, string>("INotifyPropertyChangedAttribute", "CommunityToolkit.Mvvm.ComponentModel.INotifyPropertyChangedAttribute"),
+        new KeyValuePair<string, string>("NotifyCanExecuteChangedForAttribute", "CommunityToolkit.Mvvm.ComponentModel.NotifyCanExecuteChangedForAttribute"),
+        new KeyValuePair<string, string>("NotifyDataErrorInfoAttribute", "CommunityToolkit.Mvvm.ComponentModel.NotifyDataErrorInfoAttribute"),
+        new KeyValuePair<string, string>("NotifyPropertyChangedForAttribute", "CommunityToolkit.Mvvm.ComponentModel.NotifyPropertyChangedForAttribute"),
+        new KeyValuePair<string, string>("NotifyPropertyChangedRecipientsAttribute", "CommunityToolkit.Mvvm.ComponentModel.NotifyPropertyChangedRecipientsAttribute"),
+        new KeyValuePair<string, string>("ObservableObjectAttribute", "CommunityToolkit.Mvvm.ComponentModel.ObservableObjectAttribute"),
+        new KeyValuePair<string, string>("ObservablePropertyAttribute", "CommunityToolkit.Mvvm.ComponentModel.ObservablePropertyAttribute"),
+        new KeyValuePair<string, string>("ObservableRecipientAttribute", "CommunityToolkit.Mvvm.ComponentModel.ObservableRecipientAttribute"),
+        new KeyValuePair<string, string>("RelayCommandAttribute", "CommunityToolkit.Mvvm.Input.RelayCommandAttribute"),
+    });
+
+    /// <inheritdoc/>
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = ImmutableArray.Create(UnsupportedCSharpLanguageVersionError);
+
+    /// <inheritdoc/>
+    public override void Initialize(AnalysisContext context)
+    {
+        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.Analyze | GeneratedCodeAnalysisFlags.ReportDiagnostics);
+        context.EnableConcurrentExecution();
+
+        // Defer the callback registration to when the compilation starts, so we can execute more
+        // preliminary checks and skip registering any kind of symbol analysis at all if not needed.
+        context.RegisterCompilationStartAction(static context =>
+        {
+            // Check that the language version is not high enough, otherwise no diagnostic should ever be produced
+            if (context.Compilation.HasLanguageVersionAtLeastEqualTo(LanguageVersion.CSharp8))
+            {
+                return;
+            }
+
+            context.RegisterSymbolAction(static context =>
+            {
+                // The possible attribute targets are only fields, classes and methods
+                if (context.Symbol is not (IFieldSymbol or INamedTypeSymbol { TypeKind: TypeKind.Class, IsImplicitlyDeclared: false } or IMethodSymbol))
+                {
+                    return;
+                }
+
+                ImmutableArray<AttributeData> attributes = context.Symbol.GetAttributes();
+
+                // If the symbol has no attributes, there's nothing left to do
+                if (attributes.IsEmpty)
+                {
+                    return;
+                }
+
+                foreach (AttributeData attribute in attributes)
+                {
+                    // Go over each attribute on the target symbol, and check if the attribute type name is a candidate.
+                    // If it is, double check by actually resolving the symbol from the compilation and comparing against it.
+                    // This minimizes the calls to CompilationGetTypeByMetadataName(string) to only cases where it's almost
+                    // guaranteed we'll actually get a match. If we do have one, then we can emit the diagnostic for the symbol.
+                    if (attribute.AttributeClass is { Name: string attributeName } attributeClass &&
+                        GeneratorAttributeNamesToFullyQualifiedNamesMap.TryGetValue(attributeName, out string? fullyQualifiedAttributeName) &&
+                        context.Compilation.GetTypeByMetadataName(fullyQualifiedAttributeName) is INamedTypeSymbol attributeSymbol &&
+                        SymbolEqualityComparer.Default.Equals(attributeClass, attributeSymbol))
+                    {
+                        context.ReportDiagnostic(Diagnostic.Create(UnsupportedCSharpLanguageVersionError, context.Symbol.Locations.FirstOrDefault()));
+
+                        // If we created a diagnostic for this symbol, we can stop. Even if there's multiple attributes, no need for repeated errors
+                        return;
+                    }
+                }
+            }, SymbolKind.Field, SymbolKind.NamedType, SymbolKind.Method);
+        });
+    }
+}

CommunityToolkit.Mvvm.SourceGenerators/Extensions/CompilationExtensions.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
 
 namespace CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 
@@ -11,6 +12,17 @@ namespace CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 /// </summary>
 internal static class CompilationExtensions
 {
+    /// <summary>
+    /// Checks whether a given compilation (assumed to be for C#) is using at least a given language version.
+    /// </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 at least the specified language version.</returns>
+    public static bool HasLanguageVersionAtLeastEqualTo(this Compilation compilation, LanguageVersion languageVersion)
+    {
+        return ((CSharpCompilation)compilation).LanguageVersion >= languageVersion;
+    }
+
     /// <summary>
     /// <para>
     /// Checks whether or not a type with a specified metadata name is accessible from a given <see cref="Compilation"/> instance.

CommunityToolkit.Mvvm.SourceGenerators/Extensions/IncrementalGeneratorInitializationContextExtensions.cs

@@ -5,7 +5,6 @@
 using System;
 using System.Collections.Immutable;
 using Microsoft.CodeAnalysis;
-using Microsoft.CodeAnalysis.CSharp;
 
 namespace CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 
@@ -14,54 +13,6 @@ namespace CommunityToolkit.Mvvm.SourceGenerators.Extensions;
 /// </summary>
 internal static class IncrementalGeneratorInitializationContextExtensions
 {
-    /// <summary>
-    /// Implements a gate for a language version over items in an input <see cref="IncrementalValuesProvider{TValues}"/> source.
-    /// </summary>
-    /// <typeparam name="T">The type of items in the input <see cref="IncrementalValuesProvider{TValues}"/> source.</typeparam>
-    /// <param name="context">The input <see cref="IncrementalGeneratorInitializationContext"/> value being used.</param>
-    /// <param name="source">The source <see cref="IncrementalValuesProvider{TValues}"/> instance.</param>
-    /// <param name="languageVersion">The minimum language version to gate for.</param>
-    /// <param name="diagnosticDescriptor">The <see cref="DiagnosticDescriptor"/> to emit if the gate detects invalid usage.</param>
-    /// <remarks>
-    /// Items in <paramref name="source"/> will be filtered out if the gate fails. If it passes, items will remain untouched.
-    /// </remarks>
-    public static void FilterWithLanguageVersion<T>(
-        this IncrementalGeneratorInitializationContext context,
-        ref IncrementalValuesProvider<T> source,
-        LanguageVersion languageVersion,
-        DiagnosticDescriptor diagnosticDescriptor)
-    {
-        // Check whether the target language version is supported
-        IncrementalValueProvider<bool> isGeneratorSupported =
-            context.ParseOptionsProvider
-            .Select((item, _) => item is CSharpParseOptions options && options.LanguageVersion >= languageVersion);
-
-        // Combine each data item with the supported flag
-        IncrementalValuesProvider<(T Data, bool IsGeneratorSupported)> dataWithSupportedInfo =
-            source
-            .Combine(isGeneratorSupported);
-
-        // Get a marker node to show whether an invalid attribute is used
-        IncrementalValueProvider<bool> isUnsupportedAttributeUsed =
-            dataWithSupportedInfo
-            .Select(static (item, _) => item.IsGeneratorSupported)
-            .Where(static item => !item)
-            .Collect()
-            .Select(static (item, _) => item.Length > 0);
-
-        // Report them to the output
-        context.RegisterConditionalSourceOutput(isUnsupportedAttributeUsed, context =>
-        {
-            context.ReportDiagnostic(Diagnostic.Create(diagnosticDescriptor, null));
-        });
-
-        // Only let data through if the minimum language version is supported
-        source =
-            dataWithSupportedInfo
-            .Where(static item => item.IsGeneratorSupported)
-            .Select(static (item, _) => item.Data);
-    }
-
     /// <summary>
     /// Conditionally invokes <see cref="IncrementalGeneratorInitializationContext.RegisterSourceOutput{TSource}(IncrementalValueProvider{TSource}, Action{SourceProductionContext, TSource})"/>
     /// if the value produced by the input <see cref="IncrementalValueProvider{TValue}"/> is <see langword="true"/>.

CommunityToolkit.Mvvm.SourceGenerators/Input/RelayCommandGenerator.cs

@@ -11,7 +11,6 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
-using static CommunityToolkit.Mvvm.SourceGenerators.Diagnostics.DiagnosticDescriptors;
 
 namespace CommunityToolkit.Mvvm.SourceGenerators;
 
@@ -29,7 +28,16 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             context.SyntaxProvider
             .CreateSyntaxProvider(
                 static (node, _) => node is MethodDeclarationSyntax { Parent: ClassDeclarationSyntax, AttributeLists.Count: > 0 },
-                static (context, _) => (IMethodSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!);
+                static (context, _) =>
+                {
+                    if (!context.SemanticModel.Compilation.HasLanguageVersionAtLeastEqualTo(LanguageVersion.CSharp8))
+                    {
+                        return default;
+                    }
+
+                    return (IMethodSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!;
+                })
+            .Where(static item => item is not null)!;
 
         // Filter the methods using [RelayCommand]
         IncrementalValuesProvider<(IMethodSymbol Symbol, AttributeData Attribute)> methodSymbolsWithAttributeData =
@@ -39,9 +47,6 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
                 Attribute: item.GetAttributes().FirstOrDefault(a => a.AttributeClass?.HasFullyQualifiedName("global::CommunityToolkit.Mvvm.Input.RelayCommandAttribute") == true)))
             .Where(static item => item.Attribute is not null)!;
 
-        // Filter by language version
-        context.FilterWithLanguageVersion(ref methodSymbolsWithAttributeData, LanguageVersion.CSharp8, UnsupportedCSharpLanguageVersionError);
-
         // Gather info for all annotated command methods
         IncrementalValuesProvider<(HierarchyInfo Hierarchy, Result<CommandInfo?> Info)> commandInfoWithErrors =
             methodSymbolsWithAttributeData

CommunityToolkit.Mvvm.SourceGenerators/Messaging/IMessengerRegisterAllGenerator.cs

@@ -31,7 +31,15 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             context.SyntaxProvider
             .CreateSyntaxProvider(
                 static (node, _) => node is ClassDeclarationSyntax,
-                static (context, _) => (context.Node, Symbol: (INamedTypeSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!))
+                static (context, _) =>
+                {
+                    if (!context.SemanticModel.Compilation.HasLanguageVersionAtLeastEqualTo(LanguageVersion.CSharp8))
+                    {
+                        return default;
+                    }
+
+                    return (context.Node, Symbol: (INamedTypeSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!);
+                })
             .Where(static item => item.Symbol is { IsAbstract: false, IsGenericType: false } && item.Node.IsFirstSyntaxDeclarationForSymbol(item.Symbol))
             .Select(static (item, _) => item.Symbol);
 

azure-pipelines.yml

@@ -47,12 +47,12 @@ jobs:
     displayName: Run .NET 6 unit tests
 
   # Run the .NET 6 MVVM Toolkit tests targeting Roslyn 4.0.1
-  - script: dotnet test tests\CommunityToolkit.Mvvm.UnitTests\CommunityToolkit.Mvvm.UnitTests.csproj -c Release -f net6.0 -l "trx;LogFileName=VSTestResults_net6.0_mvvmtoolkit_roslyn401.trx"
+  - script: dotnet test tests\CommunityToolkit.Mvvm.UnitTests\CommunityToolkit.Mvvm.UnitTests.csproj -c Release -f net6.0 -p:MvvmToolkitSourceGeneratorRoslynVersion=4.0.1 -l "trx;LogFileName=VSTestResults_net6.0_mvvmtoolkit_roslyn401.trx"
     displayName: Run CommunityToolkit.Mvvm.UnitTests unit tests with Roslyn 4.0.1
 
   # Run the .NET 6 MVVM Toolkit source generator tests targeting Roslyn 4.0.1
-  - script: dotnet test tests\CommunityToolkit.Mvvm.SourceGenerators.UnitTests\CommunityToolkit.Mvvm.SourceGenerators.UnitTests.csproj -c Release -f net6.0 -l "trx;LogFileName=VSTestResults_net6.0_mvvmtoolkit_generators_roslyn401.trx"
-    displayName: Run CommunityToolkit.Mvvm.UnitTests unit tests with Roslyn 4.0.1
+  - script: dotnet test tests\CommunityToolkit.Mvvm.SourceGenerators.UnitTests\CommunityToolkit.Mvvm.SourceGenerators.UnitTests.csproj -c Release -f net6.0 -p:MvvmToolkitSourceGeneratorRoslynVersion=4.0.1 -l "trx;LogFileName=VSTestResults_net6.0_mvvmtoolkit_generators_roslyn401.trx"
+    displayName: Run CommunityToolkit.Mvvm.SourceGenerators.UnitTests unit tests with Roslyn 4.0.1
 
   # Run .NET Core 3.1 tests
   - script: dotnet test -c Release -f netcoreapp3.1 -l "trx;LogFileName=VSTestResults_netcoreapp3.1.trx"

tests/CommunityToolkit.Mvvm.SourceGenerators.UnitTests/CommunityToolkit.Mvvm.SourceGenerators.UnitTests.csproj

@@ -5,6 +5,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Analyzer.Testing.MSTest" Version="1.1.1" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.0.1" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.0.0" />
     <PackageReference Include="MSTest.TestAdapter" Version="2.2.8" />