Add analyzer/fixer to suggest using cached SearchValues instances (#6898

)

* Initial Analyzer implementation

* Code fixer

* Add support for string.IndexOfAny(char[])

* Catch simple cases of array element modification

* Use built-in helper instead of Linq

* Also detect field assignments in ctor

* Move system namespace import to helper method

* Replace array creations wtih string literals

* Add support for more property getter patterns

* Simplify test helper

* Revert Utf8String support :(

* Update tests

* msbuild /t:pack /v:m

* Fix editor renaming

* Exclude string uses on a conditional access

* Add test for array field with const char reference

* Add back Utf8String support

* Update messages/descriptions

* Add support for field initialized from literal.ToCharArray

* More tests for ToCharArray

* Better handle member names that start with _

* Avoid some duplication between Syntax and Operation analysis

* Fix top-level statements and add logic to remove unused members

* ImmutableHashSet, no OfType

* Remove some duplication

* Turn one analyzer test into code fixer tests

* Shorten analyzer title

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

@@ -0,0 +1,133 @@
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the MIT license.  See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using Analyzer.Utilities.Extensions;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Operations;
+using Microsoft.NetCore.Analyzers.Performance;
+
+namespace Microsoft.NetCore.CSharp.Analyzers.Performance
+{
+    /// <inheritdoc/>
+    [ExportCodeFixProvider(LanguageNames.CSharp)]
+    public sealed class CSharpUseSearchValuesFixer : UseSearchValuesFixer
+    {
+        protected override async ValueTask<(SyntaxNode TypeDeclaration, INamedTypeSymbol? TypeSymbol, bool IsRealType)> GetTypeSymbolAsync(SemanticModel semanticModel, SyntaxNode node, CancellationToken cancellationToken)
+        {
+            SyntaxNode? typeDeclarationOrCompilationUnit = node.FirstAncestorOrSelf<TypeDeclarationSyntax>();
+
+            typeDeclarationOrCompilationUnit ??= await node.SyntaxTree.GetRootAsync(cancellationToken).ConfigureAwait(false);
+
+            return typeDeclarationOrCompilationUnit is TypeDeclarationSyntax typeDeclaration
+                ? (typeDeclaration, semanticModel.GetDeclaredSymbol(typeDeclaration, cancellationToken), IsRealType: true)
+                : (typeDeclarationOrCompilationUnit, semanticModel.GetDeclaredSymbol((CompilationUnitSyntax)typeDeclarationOrCompilationUnit, cancellationToken)?.ContainingType, IsRealType: false);
+        }
+
+        protected override SyntaxNode ReplaceSearchValuesFieldName(SyntaxNode node)
+        {
+            if (node is FieldDeclarationSyntax fieldDeclaration &&
+                fieldDeclaration.Declaration is { } declaration &&
+                declaration.Variables is [var declarator])
+            {
+                var newDeclarator = declarator.ReplaceToken(declarator.Identifier, declarator.Identifier.WithAdditionalAnnotations(RenameAnnotation.Create()));
+                return fieldDeclaration.WithDeclaration(declaration.WithVariables(new SeparatedSyntaxList<VariableDeclaratorSyntax>().Add(newDeclarator)));
+            }
+
+            return node;
+        }
+
+        protected override SyntaxNode GetDeclaratorInitializer(SyntaxNode syntax)
+        {
+            if (syntax is VariableDeclaratorSyntax variableDeclarator)
+            {
+                return variableDeclarator.Initializer!.Value;
+            }
+
+            if (syntax is PropertyDeclarationSyntax propertyDeclaration)
+            {
+                return CSharpUseSearchValuesAnalyzer.TryGetPropertyGetterExpression(propertyDeclaration)!;
+            }
+
+            throw new InvalidOperationException($"Expected 'VariableDeclaratorSyntax' or 'PropertyDeclarationSyntax', got {syntax.GetType().Name}");
+        }
+
+        // new[] { 'a', 'b', 'c' } => "abc"
+        // new[] { (byte)'a', (byte)'b', (byte)'c' } => "abc"u8
+        // "abc".ToCharArray() => "abc"
+        protected override SyntaxNode? TryReplaceArrayCreationWithInlineLiteralExpression(IOperation operation)
+        {
+            if (operation is IConversionOperation conversion)
+            {
+                operation = conversion.Operand;
+            }
+
+            if (operation is IArrayCreationOperation arrayCreation &&
+                arrayCreation.GetElementType() is { } elementType)
+            {
+                bool isByte = elementType.SpecialType == SpecialType.System_Byte;
+
+                if (isByte &&
+                    (operation.SemanticModel?.Compilation is not CSharpCompilation compilation ||
+                    compilation.LanguageVersion < (LanguageVersion)1100)) // LanguageVersion.CSharp11
+                {
+                    // Can't use Utf8StringLiterals
+                    return null;
+                }
+
+                List<char> values = new();
+
+                if (arrayCreation.Syntax is ExpressionSyntax creationSyntax &&
+                    CSharpUseSearchValuesAnalyzer.IsConstantByteOrCharArrayCreationExpression(operation.SemanticModel!, creationSyntax, values, out _) &&
+                    values.Count <= 128 &&                  // Arbitrary limit to avoid emitting huge literals
+                    !ContainsAnyComments(creationSyntax))   // Avoid removing potentially valuable comments
+                {
+                    string valuesString = string.Concat(values);
+                    string stringLiteral = SymbolDisplay.FormatLiteral(valuesString, quote: true);
+
+                    const SyntaxKind Utf8StringLiteralExpression = (SyntaxKind)8756;
+                    const SyntaxKind Utf8StringLiteralToken = (SyntaxKind)8520;
+
+                    return SyntaxFactory.LiteralExpression(
+                        isByte ? Utf8StringLiteralExpression : SyntaxKind.StringLiteralExpression,
+                        SyntaxFactory.Token(
+                            leading: default,
+                            kind: isByte ? Utf8StringLiteralToken : SyntaxKind.StringLiteralToken,
+                            text: isByte ? $"{stringLiteral}u8" : stringLiteral,
+                            valueText: valuesString,
+                            trailing: default));
+                }
+            }
+            else if (operation is IInvocationOperation invocation)
+            {
+                if (UseSearchValuesAnalyzer.IsConstantStringToCharArrayInvocation(invocation, out _))
+                {
+                    Debug.Assert(invocation.Instance is not null);
+                    return invocation.Instance!.Syntax;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool ContainsAnyComments(SyntaxNode node)
+        {
+            foreach (SyntaxTrivia trivia in node.DescendantTrivia(node.Span))
+            {
+                if (trivia.Kind() is SyntaxKind.SingleLineCommentTrivia or SyntaxKind.MultiLineCommentTrivia)
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+    }
+}

src/NetAnalyzers/CSharp/Microsoft.NetCore.Analyzers/Performance/CSharpUseSearchValues.cs

@@ -0,0 +1,221 @@
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the MIT license.  See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Operations;
+using Microsoft.NetCore.Analyzers.Performance;
+
+namespace Microsoft.NetCore.CSharp.Analyzers.Performance
+{
+    /// <inheritdoc/>
+    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public sealed class CSharpUseSearchValuesAnalyzer : UseSearchValuesAnalyzer
+    {
+        // char[] myField = new char[] { 'a', 'b', 'c' };
+        // char[] myField = new[] { 'a', 'b', 'c' };
+        // char[] myField = "abc".ToCharArray();
+        // char[] myField = ConstString.ToCharArray();
+        // byte[] myField = new[] { (byte)'a', (byte)'b', (byte)'c' };
+        protected override bool IsConstantByteOrCharArrayVariableDeclaratorSyntax(SemanticModel semanticModel, SyntaxNode syntax, out int length)
+        {
+            length = 0;
+
+            return
+                syntax is VariableDeclaratorSyntax variableDeclarator &&
+                variableDeclarator.Initializer?.Value is { } initializer &&
+                IsConstantByteOrCharArrayCreationExpression(semanticModel, initializer, values: null, out length);
+        }
+
+        // ReadOnlySpan<char> myProperty => new char[] { 'a', 'b', 'c' };
+        // ReadOnlySpan<char> myProperty => new[] { 'a', 'b', 'c' };
+        // ReadOnlySpan<char> myProperty => "abc".ToCharArray();
+        // ReadOnlySpan<char> myProperty => ConstString.ToCharArray();
+        // ReadOnlySpan<byte> myProperty => new[] { (byte)'a', (byte)'b', (byte)'c' };
+        // ReadOnlySpan<byte> myProperty => "abc"u8;
+        // ReadOnlySpan<byte> myProperty { get => "abc"u8; }
+        // ReadOnlySpan<byte> myProperty { get { return "abc"u8; } }
+        protected override bool IsConstantByteOrCharReadOnlySpanPropertyDeclarationSyntax(SemanticModel semanticModel, SyntaxNode syntax, out int length)
+        {
+            length = 0;
+
+            return
+                syntax is PropertyDeclarationSyntax propertyDeclaration &&
+                TryGetPropertyGetterExpression(propertyDeclaration) is { } expression &&
+                (IsConstantByteOrCharArrayCreationExpression(semanticModel, expression, values: null, out length) || IsUtf8StringLiteralExpression(expression, out length));
+        }
+
+        protected override bool IsConstantByteOrCharArrayCreationSyntax(SemanticModel semanticModel, SyntaxNode syntax, out int length)
+        {
+            length = 0;
+
+            return
+                syntax is ExpressionSyntax expression &&
+                IsConstantByteOrCharArrayCreationExpression(semanticModel, expression, values: null, out length);
+        }
+
+        internal static ExpressionSyntax? TryGetPropertyGetterExpression(PropertyDeclarationSyntax propertyDeclaration)
+        {
+            var expression = propertyDeclaration.ExpressionBody?.Expression;
+
+            if (expression is null &&
+                propertyDeclaration.AccessorList?.Accessors is [var accessor] &&
+                accessor.IsKind(SyntaxKind.GetAccessorDeclaration))
+            {
+                expression = accessor.ExpressionBody?.Expression;
+
+                if (expression is null &&
+                    accessor.Body?.Statements is [var statement] &&
+                    statement is ReturnStatementSyntax returnStatement)
+                {
+                    expression = returnStatement.Expression;
+                }
+            }
+
+            return expression;
+        }
+
+        // new char[] { 'a', 'b', 'c' };
+        // new[] { 'a', 'b', 'c' };
+        // new[] { (byte)'a', (byte)'b', (byte)'c' };
+        // "abc".ToCharArray()
+        // ConstString.ToCharArray()
+        internal static bool IsConstantByteOrCharArrayCreationExpression(SemanticModel semanticModel, ExpressionSyntax expression, List<char>? values, out int length)
+        {
+            length = 0;
+
+            InitializerExpressionSyntax? arrayInitializer = null;
+
+            if (expression is ArrayCreationExpressionSyntax arrayCreation)
+            {
+                arrayInitializer = arrayCreation.Initializer;
+            }
+            else if (expression is ImplicitArrayCreationExpressionSyntax implicitArrayCreation)
+            {
+                arrayInitializer = implicitArrayCreation.Initializer;
+            }
+            else if (expression is InvocationExpressionSyntax invocation)
+            {
+                if (semanticModel.GetOperation(invocation) is IInvocationOperation invocationOperation &&
+                    IsConstantStringToCharArrayInvocation(invocationOperation, out string? value))
+                {
+                    values?.AddRange(value);
+                    length = value.Length;
+                    return true;
+                }
+            }
+
+            if (arrayInitializer?.Expressions is { } valueExpressions)
+            {
+                foreach (var valueExpression in valueExpressions)
+                {
+                    if (!TryGetByteOrCharLiteral(valueExpression, out char value))
+                    {
+                        return false;
+                    }
+
+                    values?.Add(value);
+                }
+
+                length = valueExpressions.Count;
+                return true;
+            }
+
+            return false;
+
+            // 'a' or (byte)'a'
+            static bool TryGetByteOrCharLiteral(ExpressionSyntax? expression, out char value)
+            {
+                if (expression is not null)
+                {
+                    if (expression is CastExpressionSyntax cast &&
+                        cast.Type is PredefinedTypeSyntax predefinedType &&
+                        predefinedType.Keyword.IsKind(SyntaxKind.ByteKeyword))
+                    {
+                        expression = cast.Expression;
+                    }
+
+                    if (expression.IsKind(SyntaxKind.CharacterLiteralExpression) &&
+                        expression is LiteralExpressionSyntax characterLiteral &&
+                        characterLiteral.Token.Value is char charValue)
+                    {
+                        value = charValue;
+                        return true;
+                    }
+                }
+
+                value = default;
+                return false;
+            }
+        }
+
+        private static bool IsUtf8StringLiteralExpression(ExpressionSyntax expression, out int length)
+        {
+            const SyntaxKind Utf8StringLiteralExpression = (SyntaxKind)8756;
+            const SyntaxKind Utf8StringLiteralToken = (SyntaxKind)8520;
+
+            if (expression.IsKind(Utf8StringLiteralExpression) &&
+                expression is LiteralExpressionSyntax literal &&
+                literal.Token.IsKind(Utf8StringLiteralToken) &&
+                literal.Token.Value is string value)
+            {
+                length = value.Length;
+                return true;
+            }
+
+            length = 0;
+            return false;
+        }
+
+        protected override bool ArrayFieldUsesAreLikelyReadOnly(SyntaxNode syntax)
+        {
+            if (syntax is not VariableDeclaratorSyntax variableDeclarator ||
+                variableDeclarator.Identifier.Value is not string fieldName ||
+                syntax.FirstAncestorOrSelf<TypeDeclarationSyntax>() is not { } typeDeclaration)
+            {
+                return false;
+            }
+
+            // An optimistic implementation that only looks for simple assignments to the field or its array elements.
+            foreach (var member in typeDeclaration.Members)
+            {
+                bool isCtor = member.IsKind(SyntaxKind.ConstructorDeclaration);
+
+                foreach (var node in member.DescendantNodes())
+                {
+                    if (node.IsKind(SyntaxKind.SimpleAssignmentExpression) &&
+                        node is AssignmentExpressionSyntax assignment)
+                    {
+                        if (assignment.Left.IsKind(SyntaxKind.ElementAccessExpression))
+                        {
+                            if (assignment.Left is ElementAccessExpressionSyntax elementAccess &&
+                                IsFieldReference(elementAccess.Expression, fieldName))
+                            {
+                                // s_array[42] = foo;
+                                return false;
+                            }
+                        }
+                        else if (isCtor)
+                        {
+                            if (IsFieldReference(assignment.Left, fieldName))
+                            {
+                                // s_array = foo;
+                                return false;
+                            }
+                        }
+                    }
+                }
+            }
+
+            return true;
+
+            static bool IsFieldReference(ExpressionSyntax expression, string fieldName) =>
+                expression.IsKind(SyntaxKind.IdentifierName) &&
+                expression is IdentifierNameSyntax identifierName &&
+                identifierName.Identifier.Value is string value &&
+                value == fieldName;
+        }
+    }
+}

src/NetAnalyzers/Core/AnalyzerReleases.Unshipped.md

@@ -23,6 +23,7 @@ CA1861 | Performance | Info | AvoidConstArrays, [Documentation](https://learn.mi
 CA1862 | Performance | Info | RecommendCaseInsensitiveStringComparison, [Documentation](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1862)
 CA1863 | Performance | Hidden | UseCompositeFormatAnalyzer, [Documentation](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1862)
 CA1864 | Performance | Info | PreferDictionaryTryAddValueOverGuardedAddAnalyzer, [Documentation](https://docs.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1864)
+CA1870 | Performance | Info | UseSearchValuesAnalyzer, [Documentation](https://docs.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1870)
 CA2021 | Reliability | Warning | DoNotCallEnumerableCastOrOfTypeWithIncompatibleTypesAnalyzer, [Documentation](https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca2021)
 
 ### Removed Rules

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

@@ -1916,6 +1916,18 @@ Widening and user defined conversions are not supported with generic types.</val
   <data name="UseSpanClearInsteadOfFillTitle" xml:space="preserve">
     <value>Prefer 'Clear' over 'Fill'</value>
   </data>
+  <data name="UseSearchValuesTitle" xml:space="preserve">
+    <value>Use a cached 'SearchValues' instance</value>
+  </data>
+  <data name="UseSearchValuesMessage" xml:space="preserve">
+    <value>Use a cached 'SearchValues' instance for improved searching performance</value>
+  </data>
+  <data name="UseSearchValuesDescription" xml:space="preserve">
+    <value>Using a cached 'SearchValues' instance is more efficient than passing values to 'IndexOfAny'/'ContainsAny' directly.</value>
+  </data>
+  <data name="UseSearchValuesCodeFixTitle" xml:space="preserve">
+    <value>Use 'SearchValues'</value>
+  </data>
   <data name="PreventNumericIntPtrUIntPtrBehavioralChangesDescription" xml:space="preserve">
     <value>Some built-in operators added in .NET 7 behave differently when overflowing than did the corresponding user-defined operators in .NET 6 and earlier versions. Some operators that previously threw in an unchecked context now don't throw unless wrapped within a checked context. Also, some operators that did not previously throw in a checked context now throw unless wrapped in an unchecked context.</value>
   </data>