Refactor (#94)

CliFx.Analyzers/OptionMustBeInsideCommandAnalyzer.cs

@@ -0,0 +1,53 @@
+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 OptionMustBeInsideCommandAnalyzer : AnalyzerBase
+    {
+        public OptionMustBeInsideCommandAnalyzer()
+            : base(
+                "Options must be defined inside commands",
+                $"This option must be defined inside a class that implements `{SymbolNames.CliFxCommandInterface}`.")
+        {
+        }
+
+        private void Analyze(SyntaxNodeAnalysisContext context)
+        {
+            if (context.Node is not PropertyDeclarationSyntax propertyDeclaration)
+                return;
+
+            var property = context.SemanticModel.GetDeclaredSymbol(propertyDeclaration);
+            if (property is null)
+                return;
+
+            if (property.ContainingType.IsAbstract)
+                return;
+
+            if (!CommandOptionSymbol.IsOptionProperty(property))
+                return;
+
+            var isInsideCommand = property
+                .ContainingType
+                .AllInterfaces
+                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxCommandInterface));
+
+            if (!isInsideCommand)
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+
+        public override void Initialize(AnalysisContext context)
+        {
+            base.Initialize(context);
+            context.RegisterSyntaxNodeAction(Analyze, SyntaxKind.PropertyDeclaration);
+        }
+    }
+}