mROA/mROA.Codegen/SampleIncrementalSourceGenerator.cs

using System;
using System.Collections.Immutable;
using System.Linq;
using System.Text;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Text;


namespace mROA.Codegen;

/// <summary>
/// A sample source generator that creates a custom report based on class properties. The target class should be annotated with the 'Generators.ReportAttribute' attribute.
/// When using the source code as a baseline, an incremental source generator is preferable because it reduces the performance overhead.
/// </summary>
[Generator]
public class SampleIncrementalSourceGenerator : IIncrementalGenerator
{
    private const string Namespace = "mROA.Implementation";
    private const string AttributeName = "SharedObjectInterafceAttribute";

    private const string AttributeSourceCode = $@"// <auto-generated/>

namespace {Namespace}
{{
    [System.AttributeUsage(System.AttributeTargets.Class)]
    public class {AttributeName} : System.Attribute
    {{
    }}
}}";

    public void Initialize(IncrementalGeneratorInitializationContext context)
    {
        
        // Filter classes annotated with the [Report] attribute. Only filtered Syntax Nodes can trigger code generation.
        var provider = context.SyntaxProvider
            .CreateSyntaxProvider(
                (s, _) => s is InterfaceDeclarationSyntax,
                (ctx, _) => GetClassDeclarationForSourceGen(ctx))
            .Where(t => t.reportAttributeFound)
            .Select((t, _) => t.Item1);

        // Generate the source code.
        context.RegisterSourceOutput(context.CompilationProvider.Combine(provider.Collect()),
            ((ctx, t) => GenerateCode(ctx, t.Left, t.Right)));
    }

    /// <summary>
    /// Checks whether the Node is annotated with the [Report] attribute and maps syntax context to the specific node type (ClassDeclarationSyntax).
    /// </summary>
    /// <param name="context">Syntax context, based on CreateSyntaxProvider predicate</param>
    /// <returns>The specific cast and whether the attribute was found.</returns>
    private static (InterfaceDeclarationSyntax, bool reportAttributeFound) GetClassDeclarationForSourceGen(
        GeneratorSyntaxContext context)
    {
        var classDeclarationSyntax = (InterfaceDeclarationSyntax)context.Node;

        // Go through all attributes of the class.
        foreach (AttributeListSyntax attributeListSyntax in classDeclarationSyntax.AttributeLists)
        foreach (AttributeSyntax attributeSyntax in attributeListSyntax.Attributes)
        {
            if (context.SemanticModel.GetSymbolInfo(attributeSyntax).Symbol is not IMethodSymbol attributeSymbol)
                continue; // if we can't get the symbol, ignore it

            string attributeName = attributeSymbol.ContainingType.ToDisplayString();

            // Check the full name of the [Report] attribute.
            if (attributeName == "mROA.Implementation.SharedObjectInterfaceAttribute")
                return (classDeclarationSyntax, true);
        }

        return (classDeclarationSyntax, false);
    }

    /// <summary>
    /// Generate code action.
    /// It will be executed on specific nodes (ClassDeclarationSyntax annotated with the [Report] attribute) changed by the user.
    /// </summary>
    /// <param name="context">Source generation context used to add source files.</param>
    /// <param name="compilation">Compilation used to provide access to the Semantic Model.</param>
    /// <param name="classDeclarations">Nodes annotated with the [Report] attribute that trigger the generate action.</param>
    private void GenerateCode(SourceProductionContext context, Compilation compilation,
        ImmutableArray<InterfaceDeclarationSyntax> classDeclarations)
    {
        // Go through all filtered class declarations.
        foreach (var classDeclarationSyntax in classDeclarations)
        {
            // We need to get semantic model of the class to retrieve metadata.
            var semanticModel = compilation.GetSemanticModel(classDeclarationSyntax.SyntaxTree);

            // Symbols allow us to get the compile-time information.
            if (semanticModel.GetDeclaredSymbol(classDeclarationSyntax) is not INamedTypeSymbol classSymbol)
                continue;

            var namespaceName = classSymbol.ContainingNamespace.ToDisplayString();

            // 'Identifier' means the token of the node. Get class name from the syntax node.
            var className = classDeclarationSyntax.Identifier.Text;

            // Go through all class members with a particular type (property) to generate method lines.
            var methodBody = classSymbol.GetMembers()
                .OfType<IMethodSymbol>();
            Console.WriteLine(methodBody.Select(i => i.ToDisplayString()));

            var originalName = className;
            // Build up the source code
            className = className.TrimStart('I') + "RemoteEndpoint";
            var code = $@"// <auto-generated/>

using System;
using mROA.Implementation;
using System.Collections.Generic;

namespace {namespaceName};

partial class {className} (int id, ISerialisationModule.IFrontendSerialisationModule serialisationModule) : {originalName}, IRemoteObject
{{
    public int Id => id;
}}
";

            // Add the source code to the compilation.
            // context.AddSource($"{className}.g.cs", SourceText.From(code, Encoding.UTF8));
        }
    }
}