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LockedFieldShouldBePrivateAndReadonly.cs
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LockedFieldShouldBePrivateAndReadonly.cs
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/*
* SonarAnalyzer for .NET
* Copyright (C) 2015-2023 SonarSource SA
* mailto: contact AT sonarsource DOT com
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 3 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
namespace SonarAnalyzer.Rules.CSharp;
[DiagnosticAnalyzer(LanguageNames.CSharp)]
public sealed class LockedFieldShouldBePrivateAndReadonly : SonarDiagnosticAnalyzer
{
private const string DiagnosticId = "S2445";
private static readonly DiagnosticDescriptor Rule = DescriptorFactory.Create(DiagnosticId, "{0}");
public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => ImmutableArray.Create(Rule);
protected override void Initialize(SonarAnalysisContext context) =>
context.RegisterNodeAction(CheckLockStatement, SyntaxKind.LockStatement);
private static void CheckLockStatement(SonarSyntaxNodeReportingContext context)
{
var expression = ((LockStatementSyntax)context.Node).Expression?.RemoveParentheses();
if (IsCreation(expression))
{
ReportIssue("Locking on a new instance is a no-op.");
}
else
{
var symbol = context.SemanticModel.GetSymbolInfo(expression).Symbol;
if (IsOfTypeString(context.SemanticModel, expression))
{
ReportIssue("Strings can be interned, and should not be used for locking.");
}
else if (expression is IdentifierNameSyntax && symbol is ILocalSymbol lockedSymbol)
{
ReportIssue($"'{lockedSymbol.Name}' is a local variable, and should not be used for locking.");
}
else if (FieldNotReadonlyOrNotPrivate(expression, symbol) is { } lockedField)
{
ReportIssue(FieldInSameTypeAs(lockedField, context.ContainingSymbol?.ContainingType) is { } containingType
? $"Use members from '{containingType.ToMinimalDisplayString(context.SemanticModel, expression.SpanStart)}' for locking."
: $"'{lockedField.Name}' is not 'private readonly', and should not be used for locking.");
}
}
void ReportIssue(string message) =>
context.ReportIssue(Diagnostic.Create(Rule, expression.GetLocation(), message));
}
private static bool IsCreation(ExpressionSyntax expression) =>
expression.IsAnyKind(
SyntaxKind.ObjectCreationExpression,
SyntaxKind.AnonymousObjectCreationExpression,
SyntaxKind.ArrayCreationExpression,
SyntaxKind.ImplicitArrayCreationExpression,
SyntaxKind.QueryExpression);
private static bool IsOfTypeString(SemanticModel model, ExpressionSyntax expression) =>
expression.IsAnyKind(SyntaxKind.StringLiteralExpression, SyntaxKind.InterpolatedStringExpression)
|| expression.IsKnownType(KnownType.System_String, model);
private static IFieldSymbol FieldNotReadonlyOrNotPrivate(ExpressionSyntax expression, ISymbol symbol) =>
expression.IsAnyKind(SyntaxKind.IdentifierName, SyntaxKind.SimpleMemberAccessExpression)
&& symbol is IFieldSymbol lockedField
&& (!lockedField.IsReadOnly || lockedField.GetEffectiveAccessibility() != Accessibility.Private)
? lockedField
: null;
private static ITypeSymbol FieldInSameTypeAs(IFieldSymbol field, INamedTypeSymbol type) =>
field.ContainingType is { } fieldType && type is { } && !fieldType.Equals(type)
? type
: null;
}