CliFx/CliFx.Analyzers/CommandMustBeAnnotatedAnalyzer.cs

using System.Linq;
using CliFx.Analyzers.ObjectModel;
using CliFx.Analyzers.Utils.Extensions;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;

namespace CliFx.Analyzers
{
    [DiagnosticAnalyzer(LanguageNames.CSharp)]
    public class CommandMustBeAnnotatedAnalyzer : AnalyzerBase
    {
        public CommandMustBeAnnotatedAnalyzer()
            : base(
                $"Commands must be annotated with `{SymbolNames.CliFxCommandAttribute}`",
                $"This type must be annotated with `{SymbolNames.CliFxCommandAttribute}` in order to be a valid command.")
        {
        }

        private void Analyze(SyntaxNodeAnalysisContext context)
        {
            if (context.Node is not ClassDeclarationSyntax classDeclaration)
                return;

            var type = context.SemanticModel.GetDeclaredSymbol(classDeclaration);
            if (type is null)
                return;

            // Ignore abstract classes, because they may be used to define
            // base implementations for commands, in which case the command
            // attribute doesn't make sense.
            if (type.IsAbstract)
                return;

            var implementsCommandInterface = type
                .AllInterfaces
                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandInterface));

            var hasCommandAttribute = type
                .GetAttributes()
                .Select(a => a.AttributeClass)
                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandAttribute));

            // If the interface is implemented, but the attribute is missing,
            // then it's very likely a user error.
            if (implementsCommandInterface && !hasCommandAttribute)
            {
                context.ReportDiagnostic(CreateDiagnostic(classDeclaration.GetLocation()));
            }
        }

        public override void Initialize(AnalysisContext context)
        {
            base.Initialize(context);
            context.RegisterSyntaxNodeAction(Analyze, SyntaxKind.ClassDeclaration);
        }
    }
}