Refactor (#94)

CliFx.Analyzers/OptionMustHaveUniqueShortNameAnalyzer.cs

@@ -0,0 +1,65 @@
+using System.Linq;
+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 OptionMustHaveUniqueShortNameAnalyzer : AnalyzerBase
+    {
+        public OptionMustHaveUniqueShortNameAnalyzer()
+            : base(
+                "Options must have unique short names",
+                "This option's short name must be unique within the command (comparison IS case sensitive).")
+        {
+        }
+
+        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;
+
+            var otherProperties = property
+                .ContainingType
+                .GetMembers()
+                .OfType<IPropertySymbol>()
+                .Where(m => !m.Equals(property, SymbolEqualityComparer.Default))
+                .ToArray();
+
+            foreach (var otherProperty in otherProperties)
+            {
+                var otherOption = CommandOptionSymbol.TryResolve(otherProperty);
+                if (otherOption is null)
+                    continue;
+
+                if (otherOption.ShortName is null)
+                    continue;
+
+                if (option.ShortName == otherOption.ShortName)
+                {
+                    context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+                }
+            }
+        }
+
+        public override void Initialize(AnalysisContext context)
+        {
+            base.Initialize(context);
+            context.RegisterSyntaxNodeAction(Analyze, SyntaxKind.PropertyDeclaration);
+        }
+    }
+}