Refactor (#94)

CliFx.Analyzers/OptionMustHaveValidShortNameAnalyzer.cs

@@ -0,0 +1,47 @@
+using CliFx.Analyzers.ObjectModel;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace CliFx.Analyzers
+{
+    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public class OptionMustHaveValidShortNameAnalyzer : AnalyzerBase
+    {
+        public OptionMustHaveValidShortNameAnalyzer()
+            : base(
+                "Option short names must be letter characters",
+                "This option's short name must be a single letter character.")
+        {
+        }
+
+        private void Analyze(SyntaxNodeAnalysisContext context)
+        {
+            if (context.Node is not PropertyDeclarationSyntax propertyDeclaration)
+                return;
+
+            var property = context.SemanticModel.GetDeclaredSymbol(propertyDeclaration);
+            if (property is null)
+                return;
+
+            var option = CommandOptionSymbol.TryResolve(property);
+            if (option is null)
+                return;
+
+            if (option.ShortName is null)
+                return;
+
+            if (!char.IsLetter(option.ShortName.Value))
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+
+        public override void Initialize(AnalysisContext context)
+        {
+            base.Initialize(context);
+            context.RegisterSyntaxNodeAction(Analyze, SyntaxKind.PropertyDeclaration);
+        }
+    }
+}