Add CA1868: Unnecessary call to Set.Contains(item)

src/NetAnalyzers/CSharp/Microsoft.NetCore.Analyzers/Performance/CSharpDoNotGuardSetAddOrRemoveByContains.Fixer.cs

@@ -0,0 +1,71 @@
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the MIT license.  See License.txt in the project root for license information.
+
+using System.Composition;
+using System.Linq;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Editing;
+using Microsoft.CodeAnalysis.Formatting;
+using Microsoft.NetCore.Analyzers.Performance;
+
+namespace Microsoft.NetCore.CSharp.Analyzers.Performance
+{
+    [ExportCodeFixProvider(LanguageNames.CSharp), Shared]
+    public sealed class CSharpDoNotGuardSetAddOrRemoveByContainsFixer : DoNotGuardSetAddOrRemoveByContainsFixer
+    {
+        protected override bool SyntaxSupportedByFixer(SyntaxNode conditionalSyntax, SyntaxNode childStatementSyntax)
+        {
+            if (childStatementSyntax is not ExpressionStatementSyntax)
+            {
+                return false;
+            }
+
+            if (conditionalSyntax is IfStatementSyntax ifStatementSyntax)
+            {
+                var addOrRemoveInElse = childStatementSyntax.Parent is ElseClauseSyntax || childStatementSyntax.Parent?.Parent is ElseClauseSyntax;
+
+                return addOrRemoveInElse
+                    ? ifStatementSyntax.Else?.Statement.ChildNodes().Count() == 1
+                    : ifStatementSyntax.Statement.ChildNodes().Count() == 1;
+            }
+
+            return false;
+        }
+
+        protected override Document ReplaceConditionWithChild(Document document, SyntaxNode root, SyntaxNode conditionalOperationNode, SyntaxNode childOperationNode)
+        {
+            SyntaxNode newRoot;
+
+            if (conditionalOperationNode is IfStatementSyntax { Else: not null } ifStatementSyntax)
+            {
+                var expression = GetNegatedExpression(document, childOperationNode);
+                var addOrRemoveInElse = childOperationNode.Parent is ElseClauseSyntax || childOperationNode.Parent?.Parent is ElseClauseSyntax;
+
+                SyntaxNode newConditionalOperationNode = ifStatementSyntax
+                    .WithCondition((ExpressionSyntax)expression)
+                    .WithStatement(addOrRemoveInElse ? ifStatementSyntax.Statement : ifStatementSyntax.Else.Statement)
+                    .WithElse(null)
+                    .WithAdditionalAnnotations(Formatter.Annotation).WithTriviaFrom(conditionalOperationNode);
+
+                newRoot = root.ReplaceNode(conditionalOperationNode, newConditionalOperationNode);
+            }
+            else
+            {
+                SyntaxNode newConditionNode = childOperationNode
+                    .WithAdditionalAnnotations(Formatter.Annotation)
+                    .WithTriviaFrom(conditionalOperationNode);
+
+                newRoot = root.ReplaceNode(conditionalOperationNode, newConditionNode);
+            }
+
+            return document.WithSyntaxRoot(newRoot);
+        }
+
+        private static SyntaxNode GetNegatedExpression(Document document, SyntaxNode newConditionNode)
+        {
+            var generator = SyntaxGenerator.GetGenerator(document);
+            return generator.LogicalNotExpression(((ExpressionStatementSyntax)newConditionNode).Expression.WithoutTrivia());
+        }
+    }
+}

src/NetAnalyzers/Core/AnalyzerReleases.Unshipped.md

@@ -7,6 +7,7 @@ Rule ID | Category | Severity | Notes
 CA1865 | Performance | Info | UseStringMethodCharOverloadWithSingleCharacters, [Documentation](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1865)
 CA1866 | Performance | Info | UseStringMethodCharOverloadWithSingleCharacters, [Documentation](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1866)
 CA1867 | Performance | Disabled | UseStringMethodCharOverloadWithSingleCharacters, [Documentation](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1867)
+CA1868 | Performance | Info | DoNotGuardSetAddOrRemoveByContains, [Documentation](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1865)
 CA2261 | Usage | Warning | DoNotUseConfigureAwaitWithSuppressThrowing, [Documentation](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca2250)
 CA1510 | Maintainability | Info | UseExceptionThrowHelpers, [Documentation](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1510)
 CA1511 | Maintainability | Info | UseExceptionThrowHelpers, [Documentation](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1511)

src/NetAnalyzers/Core/Microsoft.NetCore.Analyzers/MicrosoftNetCoreAnalyzersResources.resx

@@ -1509,6 +1509,15 @@
   <data name="DoNotGuardDictionaryRemoveByContainsKeyTitle" xml:space="preserve">
     <value>Unnecessary call to 'Dictionary.ContainsKey(key)'</value>
   </data>
+  <data name="DoNotGuardSetAddOrRemoveByContainsDescription" xml:space="preserve">
+    <value>Do not guard 'Add(item)' or 'Remove(item)' with 'Contains(item)' for the set. The former two already check whether the item exists and will return if it was added or removed.</value>
+  </data>
+  <data name="DoNotGuardSetAddOrRemoveByContainsMessage" xml:space="preserve">
+    <value>Do not guard '{0}' with '{1}'</value>
+  </data>
+  <data name="DoNotGuardSetAddOrRemoveByContainsTitle" xml:space="preserve">
+    <value>Unnecessary call to 'Contains(item)'</value>
+  </data>
   <data name="RemoveRedundantGuardCallCodeFixTitle" xml:space="preserve">
     <value>Remove unnecessary call</value>
   </data>

src/NetAnalyzers/Core/Microsoft.NetCore.Analyzers/Performance/DoNotGuardSetAddOrRemoveByContains.Fixer.cs

@@ -0,0 +1,60 @@
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the MIT license.  See License.txt in the project root for license information.
+
+using System.Collections.Immutable;
+using System.Threading.Tasks;
+using Analyzer.Utilities;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CodeFixes;
+
+namespace Microsoft.NetCore.Analyzers.Performance
+{
+    public abstract class DoNotGuardSetAddOrRemoveByContainsFixer : CodeFixProvider
+    {
+        public override ImmutableArray<string> FixableDiagnosticIds { get; } =
+            ImmutableArray.Create(DoNotGuardSetAddOrRemoveByContains.RuleId);
+
+        public sealed override FixAllProvider GetFixAllProvider()
+        {
+            return WellKnownFixAllProviders.BatchFixer;
+        }
+
+        public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
+        {
+            var root = await context.Document.GetRequiredSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);
+            var node = root.FindNode(context.Span, getInnermostNodeForTie: true);
+
+            if (node is null)
+            {
+                return;
+            }
+
+            var diagnostic = context.Diagnostics[0];
+            var conditionalLocation = diagnostic.AdditionalLocations[0];
+            var childLocation = diagnostic.AdditionalLocations[1];
+
+            if (root.FindNode(conditionalLocation.SourceSpan) is not SyntaxNode conditionalSyntax ||
+                root.FindNode(childLocation.SourceSpan) is not SyntaxNode childStatementSyntax)
+            {
+                return;
+            }
+
+            if (!SyntaxSupportedByFixer(conditionalSyntax, childStatementSyntax))
+            {
+                return;
+            }
+
+            var codeAction = CodeAction.Create(MicrosoftNetCoreAnalyzersResources.RemoveRedundantGuardCallCodeFixTitle,
+                ct => Task.FromResult(ReplaceConditionWithChild(context.Document, root, conditionalSyntax, childStatementSyntax)),
+                nameof(MicrosoftNetCoreAnalyzersResources.DoNotGuardSetAddOrRemoveByContainsTitle));
+
+            context.RegisterCodeFix(codeAction, diagnostic);
+        }
+
+        protected abstract bool SyntaxSupportedByFixer(SyntaxNode conditionalSyntax, SyntaxNode childStatementSyntax);
+
+        protected abstract Document ReplaceConditionWithChild(Document document, SyntaxNode root,
+                                                              SyntaxNode conditionalOperationNode,
+                                                              SyntaxNode childOperationNode);
+    }
+}