From dbc76b15364fab248e6a009f094b1e348ef1a2e6 Mon Sep 17 00:00:00 2001
From: webbrain-one <295484252+webbrain-one@users.noreply.github.com>
Date: Sun, 16 Aug 2026 12:03:45 +0300
Subject: [PATCH] Add analyzer for switch not covering all enum values

Issue #91: report switch statements that do not cover all enum values.
---
 .../BlowinCleanCodeAnalyzer.cs                |   1 +
 ...itchNotCoverAllEnumValuesFeatureAnalyze.cs | 125 ++++++++++++++++++
 2 files changed, 126 insertions(+)
 create mode 100644 BlowinCleanCode/BlowinCleanCode/Feature/GoodPractice/SwitchNotCoverAllEnumValuesFeatureAnalyze.cs

diff --git a/BlowinCleanCode/BlowinCleanCode/BlowinCleanCodeAnalyzer.cs b/BlowinCleanCode/BlowinCleanCode/BlowinCleanCodeAnalyzer.cs
index c48d9fb..934e13a 100644
--- a/BlowinCleanCode/BlowinCleanCode/BlowinCleanCodeAnalyzer.cs
+++ b/BlowinCleanCode/BlowinCleanCode/BlowinCleanCodeAnalyzer.cs
@@ -33,6 +33,7 @@ public class BlowinCleanCodeAnalyzer : DiagnosticAnalyzer
             new StaticClassFeatureSymbolAnalyze(),
             new DisposableMemberInNonDisposableClassFeatureAnalyze(),
             new SwitchStatementsShouldHaveAtLeast2CaseClausesFeatureAnalyze(),
+            new SwitchNotCoverAllEnumValuesFeatureAnalyze(),
             new FinalizersShouldNotBeEmptyFeatureAnalyze(),
             new TypeThatProvideEqualsShouldImplementIEquatableFeatureAnalyze(),
             new ThreadStaticFieldsShouldNotBeInitializedFeatureAnalyze(),
diff --git a/BlowinCleanCode/BlowinCleanCode/Feature/GoodPractice/SwitchNotCoverAllEnumValuesFeatureAnalyze.cs b/BlowinCleanCode/BlowinCleanCode/Feature/GoodPractice/SwitchNotCoverAllEnumValuesFeatureAnalyze.cs
new file mode 100644
index 0000000..89edbcf
--- /dev/null
+++ b/BlowinCleanCode/BlowinCleanCode/Feature/GoodPractice/SwitchNotCoverAllEnumValuesFeatureAnalyze.cs
@@ -0,0 +1,125 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using BlowinCleanCode.Feature.Base;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+
+namespace BlowinCleanCode.Feature.GoodPractice
+{
+    public sealed class SwitchNotCoverAllEnumValuesFeatureAnalyze : FeatureSyntaxNodeAnalyzerBase<SwitchStatementSyntax>
+    {
+        public const string DiagnosticId = "BCC1000";
+
+        public override DiagnosticDescriptor DiagnosticDescriptor { get; } = new DiagnosticDescriptor(
+            DiagnosticId,
+            "Switch does not cover all enum values",
+            "Switch does not cover all enum values",
+            "Good practice",
+            DiagnosticSeverity.Warning,
+            "A switch statement on an enum type should handle every enum value or provide a default clause",
+            true);
+
+        protected override SyntaxKind SyntaxKind => SyntaxKind.SwitchStatement;
+
+        protected override void Analyze(SyntaxNodeAnalysisContext context, SwitchStatementSyntax syntax)
+        {
+            if (AnalyzerCommentSkipCheck.Skip(syntax))
+                return;
+
+            var enumType = context.SemanticModel.GetTypeInfo(syntax.Expression).Type as INamedTypeSymbol;
+            if (enumType == null || enumType.TypeKind != TypeKind.Enum)
+                return;
+
+            if (IsFlagsEnum(enumType))
+                return;
+
+            if (HasDefaultClause(syntax))
+                return;
+
+            var coveredValues = GetCoveredValues(context, syntax);
+            foreach (var member in enumType.GetMembers())
+            {
+                if (!(member is IFieldSymbol field) || !field.IsEnumMember)
+                    continue;
+
+                if (field.ConstantValue == null)
+                    continue;
+
+                if (TryGetValue(field.ConstantValue, out var memberValue) && coveredValues.Contains(memberValue))
+                    continue;
+
+                ReportDiagnostic(context, syntax.GetLocation());
+                return;
+            }
+        }
+
+        private static bool HasDefaultClause(SwitchStatementSyntax syntax)
+            => syntax.Sections.SelectMany(s => s.Labels).OfType<DefaultLabelSyntax>().Any();
+
+        private static bool IsFlagsEnum(INamedTypeSymbol enumType)
+            => enumType.GetAttributes().Any(a => a.AttributeClass?.ToDisplayString() == "System.FlagsAttribute");
+
+        private static HashSet<decimal> GetCoveredValues(SyntaxNodeAnalysisContext context, SwitchStatementSyntax syntax)
+        {
+            var values = new HashSet<decimal>();
+            foreach (var section in syntax.Sections)
+            {
+                foreach (var label in section.Labels)
+                {
+                    if (label is CaseLabelSyntax caseLabel && caseLabel.Value != null)
+                    {
+                        var constant = context.SemanticModel.GetConstantValue(caseLabel.Value);
+                        if (constant.HasValue && TryGetValue(constant.Value, out var value))
+                            values.Add(value);
+                    }
+                }
+            }
+
+            return values;
+        }
+
+        private static bool TryGetValue(object value, out decimal result)
+        {
+            if (value is null)
+                return false;
+
+            if (value.GetType().IsEnum)
+            {
+                value = Convert.ChangeType(value, value.GetType().BaseType, CultureInfo.InvariantCulture);
+            }
+
+            switch (value)
+            {
+                case byte b:
+                    result = b;
+                    return true;
+                case sbyte sb:
+                    result = sb;
+                    return true;
+                case short s:
+                    result = s;
+                    return true;
+                case ushort us:
+                    result = us;
+                    return true;
+                case int i:
+                    result = i;
+                    return true;
+                case uint ui:
+                    result = ui;
+                    return true;
+                case long l:
+                    result = (decimal)l;
+                    return true;
+                case ulong ul:
+                    result = (decimal)ul;
+                    return true;
+                default:
+                    return false;
+            }
+        }
+    }
+}