Add analyzer "Use enum field explicitly" (RCS1257)

ChangeLog.md

@@ -12,6 +12,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add SECURITY.md ([#1147](https://github.com/josefpihrt/roslynator/pull/1147))
 - Add custom FixAllProvider for [RCS1014](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1014.md) ([#1070](https://github.com/JosefPihrt/Roslynator/pull/1070)).
 - Add more cases to [RCS1097](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1097.md) ([#1160](https://github.com/JosefPihrt/Roslynator/pull/1160)).
+- Add analyzer "Use enum field explicitly" ([RCS1257](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1257)) ([#889](https://github.com/josefpihrt/roslynator/pull/889)).
+  - Enabled by default.
 
 ### Fixed
 

src/Analyzers.CodeFixes/CSharp/CodeFixes/CastExpressionCodeFixProvider.cs

@@ -0,0 +1,104 @@
+// Copyright (c) Josef Pihrt and Contributors. Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Composition;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Roslynator.CodeFixes;
+using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
+using static Roslynator.CSharp.CSharpFactory;
+
+namespace Roslynator.CSharp.CodeFixes;
+
+[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(CastExpressionCodeFixProvider))]
+[Shared]
+public sealed class CastExpressionCodeFixProvider : BaseCodeFixProvider
+{
+    public override ImmutableArray<string> FixableDiagnosticIds
+    {
+        get { return ImmutableArray.Create(DiagnosticIdentifiers.UseEnumFieldExplicitly); }
+    }
+
+    public override async Task RegisterCodeFixesAsync(CodeFixContext context)
+    {
+        SyntaxNode root = await context.GetSyntaxRootAsync().ConfigureAwait(false);
+
+        if (!TryFindFirstAncestorOrSelf(root, context.Span, out CastExpressionSyntax castExpression))
+            return;
+
+        Diagnostic diagnostic = context.Diagnostics[0];
+        Document document = context.Document;
+
+        CodeAction codeAction = CodeAction.Create(
+            "Use enum field explicitly",
+            ct => UseEnumFieldExplicitlyAsync(castExpression, document, ct),
+            GetEquivalenceKey(DiagnosticIdentifiers.UseEnumFieldExplicitly));
+
+        context.RegisterCodeFix(codeAction, diagnostic);
+    }
+
+    private static async Task<Document> UseEnumFieldExplicitlyAsync(
+        CastExpressionSyntax castExpression,
+        Document document,
+        CancellationToken cancellationToken)
+    {
+        SemanticModel semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
+
+        Optional<object> constantValueOpt = semanticModel.GetConstantValue(castExpression.Expression, cancellationToken);
+
+        var enumSymbol = (INamedTypeSymbol)semanticModel.GetTypeSymbol(castExpression.Type, cancellationToken);
+
+        if (enumSymbol.HasAttribute(MetadataNames.System_FlagsAttribute))
+        {
+            ulong value = SymbolUtility.GetEnumValueAsUInt64(constantValueOpt.Value, enumSymbol);
+
+            List<ulong> flags = FlagsUtility<ulong>.Instance.GetFlags(value).ToList();
+
+            List<EnumFieldSymbolInfo> fields = EnumSymbolInfo.Create(enumSymbol).Fields
+                .Where(f => flags.Contains(f.Value))
+                .OrderByDescending(f => f.Value)
+                .ToList();
+
+            ExpressionSyntax newExpression = CreateEnumFieldExpression(fields[0].Symbol);
+
+            for (int i = 1; i < fields.Count; i++)
+            {
+                newExpression = BitwiseOrExpression(
+                    CreateEnumFieldExpression(fields[i].Symbol),
+                    newExpression);
+            }
+
+            newExpression = newExpression.WithTriviaFrom(castExpression);
+
+            return await document.ReplaceNodeAsync(castExpression, newExpression, cancellationToken).ConfigureAwait(false);
+        }
+        else
+        {
+            IFieldSymbol symbol = enumSymbol
+                .GetMembers()
+                .OfType<IFieldSymbol>()
+                .First(fieldSymbol =>
+                {
+                    return fieldSymbol.HasConstantValue
+                        && constantValueOpt.Value.Equals(fieldSymbol.ConstantValue);
+                });
+
+            ExpressionSyntax newExpression = CreateEnumFieldExpression(symbol).WithTriviaFrom(castExpression);
+
+            return await document.ReplaceNodeAsync(castExpression, newExpression, cancellationToken).ConfigureAwait(false);
+        }
+
+        static MemberAccessExpressionSyntax CreateEnumFieldExpression(IFieldSymbol symbol)
+        {
+            return SimpleMemberAccessExpression(
+                symbol.Type.ToTypeSyntax().WithSimplifierAnnotation(),
+                IdentifierName(symbol.Name));
+        }
+    }
+}

src/Analyzers.xml

@@ -7356,6 +7356,18 @@ void M()
 - optional and its default value is `null`.
     </Summary>
   </Analyzer>
+  <Analyzer Identifier="UseEnumFieldExplicitly">
+    <Id>RCS1257</Id>
+    <Title>Use enum field explicitly.</Title>
+    <DefaultSeverity>Info</DefaultSeverity>
+    <IsEnabledByDefault>true</IsEnabledByDefault>
+    <Samples>
+      <Sample>
+        <Before><![CDATA[var options = (RegexOptions) 1]]></Before>
+        <After><![CDATA[var options = RegexOptions.IgnoreCase]]></After>
+      </Sample>
+    </Samples>
+  </Analyzer>
   <Analyzer>
     <Id>RCS9001</Id>
     <Identifier>UsePatternMatching</Identifier>

src/Analyzers/CSharp/Analysis/UseEnumFieldExplicitlyAnalyzer.cs

@@ -0,0 +1,94 @@
+// Copyright (c) Josef Pihrt and Contributors. Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace Roslynator.CSharp.Analysis;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class UseEnumFieldExplicitlyAnalyzer : BaseDiagnosticAnalyzer
+{
+    private static ImmutableArray<DiagnosticDescriptor> _supportedDiagnostics;
+
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics
+    {
+        get
+        {
+            if (_supportedDiagnostics.IsDefault)
+                Immutable.InterlockedInitialize(ref _supportedDiagnostics, DiagnosticRules.UseEnumFieldExplicitly);
+
+            return _supportedDiagnostics;
+        }
+    }
+
+    public override void Initialize(AnalysisContext context)
+    {
+        base.Initialize(context);
+
+        context.RegisterSyntaxNodeAction(c => AnalyzeCastExpression(c), SyntaxKind.CastExpression);
+    }
+
+    private static void AnalyzeCastExpression(SyntaxNodeAnalysisContext context)
+    {
+        var castExpression = (CastExpressionSyntax)context.Node;
+
+        ExpressionSyntax expression = castExpression.Expression;
+
+        if (expression is not LiteralExpressionSyntax literalExpression)
+            return;
+
+        string s = literalExpression.Token.Text;
+
+        if (s.Length == 0)
+            return;
+
+        if (!s.StartsWith("0x")
+            && !s.StartsWith("0X")
+            && !s.StartsWith("0b")
+            && !s.StartsWith("0B")
+            && !char.IsDigit(s[0]))
+        {
+            return;
+        }
+
+        Optional<object> constantValueOpt = context.SemanticModel.GetConstantValue(literalExpression, context.CancellationToken);
+
+        if (!constantValueOpt.HasValue)
+            return;
+
+        var enumSymbol = context.SemanticModel.GetTypeSymbol(castExpression.Type, context.CancellationToken) as INamedTypeSymbol;
+
+        if (enumSymbol?.EnumUnderlyingType is null)
+            return;
+
+        ulong value = SymbolUtility.GetEnumValueAsUInt64(constantValueOpt.Value, enumSymbol);
+
+        foreach (ISymbol member in enumSymbol.GetMembers())
+        {
+            if (member is IFieldSymbol fieldSymbol
+                && fieldSymbol.HasConstantValue
+                && value == SymbolUtility.GetEnumValueAsUInt64(fieldSymbol.ConstantValue, enumSymbol))
+            {
+                context.ReportDiagnostic(DiagnosticRules.UseEnumFieldExplicitly, castExpression);
+                return;
+            }
+        }
+
+        if (enumSymbol.HasAttribute(MetadataNames.System_FlagsAttribute)
+            && FlagsUtility<ulong>.Instance.IsComposite(value))
+        {
+            EnumSymbolInfo enumInfo = EnumSymbolInfo.Create(enumSymbol);
+
+            foreach (ulong flag in FlagsUtility<ulong>.Instance.GetFlags(value))
+            {
+                if (!enumInfo.Contains(flag))
+                    return;
+            }
+
+            context.ReportDiagnostic(DiagnosticRules.UseEnumFieldExplicitly, castExpression);
+        }
+    }
+}

src/Analyzers/CSharp/DiagnosticIdentifiers.Generated.cs

@@ -213,5 +213,6 @@ public static partial class DiagnosticIdentifiers
         public const string NormalizeFormatOfEnumFlagValue = "RCS1254";
         public const string SimplifyArgumentNullCheck = "RCS1255";
         public const string InvalidArgumentNullCheck = "RCS1256";
+        public const string UseEnumFieldExplicitly = "RCS1257";
     }
 }

src/Analyzers/CSharp/DiagnosticRules.Generated.cs

@@ -2521,5 +2521,17 @@ public static partial class DiagnosticRules
             helpLinkUri:        DiagnosticIdentifiers.InvalidArgumentNullCheck, 
             customTags:         Array.Empty<string>());
 
+        /// <summary>RCS1257</summary>
+        public static readonly DiagnosticDescriptor UseEnumFieldExplicitly = DiagnosticDescriptorFactory.Create(
+            id:                 DiagnosticIdentifiers.UseEnumFieldExplicitly, 
+            title:              "Use enum field explicitly.", 
+            messageFormat:      "Use enum field explicitly.", 
+            category:           DiagnosticCategories.Roslynator, 
+            defaultSeverity:    DiagnosticSeverity.Info, 
+            isEnabledByDefault: true, 
+            description:        null, 
+            helpLinkUri:        DiagnosticIdentifiers.UseEnumFieldExplicitly, 
+            customTags:         Array.Empty<string>());
+
     }
 }

src/Tests/Analyzers.Tests/RCS1257UseEnumFieldExplicitlyTests.cs

@@ -0,0 +1,106 @@
+// Copyright (c) Josef Pihrt and Contributors. Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Roslynator.CSharp.CodeFixes;
+using Roslynator.Testing.CSharp;
+using Xunit;
+
+namespace Roslynator.CSharp.Analysis.Tests;
+
+public class RCS1257UseEnumFieldExplicitlyTests : AbstractCSharpDiagnosticVerifier<UseEnumFieldExplicitlyAnalyzer, CastExpressionCodeFixProvider>
+{
+    public override DiagnosticDescriptor Descriptor { get; } = DiagnosticRules.UseEnumFieldExplicitly;
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseEnumFieldExplicitly)]
+    public async Task Test()
+    {
+        await VerifyDiagnosticAndFixAsync(@"
+using System.Text.RegularExpressions;
+
+class C
+{
+    void M()
+    {
+        var x = [|(RegexOptions)1|];
+    }
+}
+", @"
+using System.Text.RegularExpressions;
+
+class C
+{
+    void M()
+    {
+        var x = RegexOptions.IgnoreCase;
+    }
+}
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseEnumFieldExplicitly)]
+    public async Task Test_Flags()
+    {
+        await VerifyDiagnosticAndFixAsync(@"
+using System.Text.RegularExpressions;
+
+class C
+{
+    void M()
+    {
+        var x = [|(RegexOptions)7|];
+    }
+}
+", @"
+using System.Text.RegularExpressions;
+
+class C
+{
+    void M()
+    {
+        var x = RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.ExplicitCapture;
+    }
+}
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseEnumFieldExplicitly)]
+    public async Task TestNoDiagnostic_UndefinedValue()
+    {
+        await VerifyNoDiagnosticAsync(@"
+using System.Text.RegularExpressions;
+
+class C
+{
+    void M()
+    {
+        var x = (Foo)17;
+    }
+}
+
+[System.Flags]
+enum Foo
+{
+    None = 0,
+    A = 1,
+    B = 2,
+    C = 4,
+    D = 8,
+}
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseEnumFieldExplicitly)]
+    public async Task TestNoDiagnostic_FileAttributes()
+    {
+        await VerifyNoDiagnosticAsync(@"
+class C
+{
+    void M()
+    {
+        var x = (System.IO.FileAttributes)0;
+    }
+}
+");
+    }
+}

src/VisualStudioCode/package/src/configurationFiles.generated.ts

@@ -906,6 +906,9 @@ roslynator_analyzers.enabled_by_default = true|false
 # Invalid argument null check
 #dotnet_diagnostic.rcs1256.severity = suggestion
 
+# Use enum field explicitly
+#dotnet_diagnostic.rcs1257.severity = suggestion
+
 # Use pattern matching
 #dotnet_diagnostic.rcs9001.severity = silent