Implement CodeFixer for LockObjectsMustBeReadonlyAnalyzer

Co-authored-by: bcollamore <57269455+bcollamore@users.noreply.github.com>

Author: Copilot

Documentation/Diagnostics/PH2066.md

@@ -6,7 +6,7 @@
 | Diagnostic ID | PH2066 |
 | Category  | [Maintainability](../Maintainability.md) |
 | Analyzer | [LockObjectsMustBeReadonlyAnalyzer](https://github.com/philips-software/roslyn-analyzers/blob/main/Philips.CodeAnalysis.MaintainabilityAnalyzers/Maintainability/LockObjectsMustBeReadonlyAnalyzer.cs)
-| CodeFix  | No |
+| CodeFix  | Yes |
 | Severity | Error |
 | Enabled By Default | Yes |
 

Philips.CodeAnalysis.MaintainabilityAnalyzers/Maintainability/LockObjectsMustBeReadonlyCodeFixProvider.cs

@@ -0,0 +1,87 @@
+// © 2025 Koninklijke Philips N.V. See License.md in the project root for license information.
+
+using System.Collections.Immutable;
+using System.Composition;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Philips.CodeAnalysis.Common;
+
+namespace Philips.CodeAnalysis.MaintainabilityAnalyzers.Maintainability
+{
+	[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(LockObjectsMustBeReadonlyCodeFixProvider)), Shared]
+	public class LockObjectsMustBeReadonlyCodeFixProvider : SingleDiagnosticCodeFixProvider<IdentifierNameSyntax>
+	{
+		protected override string Title => "Add readonly modifier to field";
+
+		protected override DiagnosticId DiagnosticId => DiagnosticId.LocksShouldBeReadonly;
+
+		protected override async Task<Document> ApplyFix(Document document, IdentifierNameSyntax node, ImmutableDictionary<string, string> properties, CancellationToken cancellationToken)
+		{
+			SyntaxNode rootNode = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
+			SemanticModel semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
+
+			// Get the symbol referenced by the identifier
+			SymbolInfo symbolInfo = semanticModel.GetSymbolInfo(node, cancellationToken);
+			if (symbolInfo.Symbol is not IFieldSymbol fieldSymbol)
+			{
+				return document;
+			}
+
+			// Use the field symbol's declaration reference to find the actual syntax node
+			SyntaxReference declaringSyntaxReference = fieldSymbol.DeclaringSyntaxReferences.FirstOrDefault();
+			if (declaringSyntaxReference == null)
+			{
+				return document;
+			}
+
+			SyntaxNode declaringSyntax = await declaringSyntaxReference.GetSyntaxAsync(cancellationToken).ConfigureAwait(false);
+			FieldDeclarationSyntax fieldDeclaration = declaringSyntax.FirstAncestorOrSelf<FieldDeclarationSyntax>();
+
+			if (fieldDeclaration == null)
+			{
+				return document;
+			}
+
+			// Add readonly modifier if not already present
+			SyntaxTokenList modifiers = fieldDeclaration.Modifiers;
+			if (!modifiers.Any(m => m.IsKind(SyntaxKind.ReadOnlyKeyword)))
+			{
+				SyntaxToken readonlyModifier = SyntaxFactory.Token(SyntaxKind.ReadOnlyKeyword).WithTrailingTrivia(SyntaxFactory.Space);
+
+				// Insert readonly after access modifiers but before static
+				SyntaxTokenList newModifiers = modifiers;
+				var insertIndex = 0;
+
+				// Find appropriate position for readonly modifier
+				for (var i = 0; i < modifiers.Count; i++)
+				{
+					if (modifiers[i].IsKind(SyntaxKind.PublicKeyword) ||
+						modifiers[i].IsKind(SyntaxKind.PrivateKeyword) ||
+						modifiers[i].IsKind(SyntaxKind.ProtectedKeyword) ||
+						modifiers[i].IsKind(SyntaxKind.InternalKeyword))
+					{
+						insertIndex = i + 1;
+					}
+					else if (modifiers[i].IsKind(SyntaxKind.StaticKeyword))
+					{
+						insertIndex = i + 1;
+						break;
+					}
+				}
+
+				newModifiers = newModifiers.Insert(insertIndex, readonlyModifier);
+				FieldDeclarationSyntax newFieldDeclaration = fieldDeclaration.WithModifiers(newModifiers);
+
+				SyntaxNode newRoot = rootNode.ReplaceNode(fieldDeclaration, newFieldDeclaration);
+				return document.WithSyntaxRoot(newRoot);
+			}
+
+			return document;
+		}
+	}
+}

Philips.CodeAnalysis.Test/Maintainability/Maintainability/LockObjectsMustBeReadonlyAnalyzerTest.cs

@@ -1,6 +1,7 @@
 // © 2019 Koninklijke Philips N.V. See License.md in the project root for license information.
 
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CodeFixes;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Philips.CodeAnalysis.Common;
@@ -11,13 +12,18 @@
 namespace Philips.CodeAnalysis.Test.Maintainability.Maintainability
 {
 	[TestClass]
-	public class LockObjectsMustBeReadonlyAnalyzerTest : DiagnosticVerifier
+	public class LockObjectsMustBeReadonlyAnalyzerTest : CodeFixVerifier
 	{
 		protected override DiagnosticAnalyzer GetDiagnosticAnalyzer()
 		{
 			return new LockObjectsMustBeReadonlyAnalyzer();
 		}
 
+		protected override CodeFixProvider GetCodeFixProvider()
+		{
+			return new LockObjectsMustBeReadonlyCodeFixProvider();
+		}
+
 		[DataRow("static object _foo", true)]
 		[DataRow("object _foo", true)]
 		[DataRow("static readonly object _foo", false)]
@@ -155,5 +161,110 @@ public void Test()
 ";
 			await VerifyDiagnostic(template, DiagnosticId.LocksShouldBeReadonly, regex: "'_foo'").ConfigureAwait(false);
 		}
+
+		[TestMethod]
+		[TestCategory(TestDefinitions.UnitTests)]
+		public async Task LockObjectsMustBeReadonlyCodeFixPrivateFieldAsync()
+		{
+			const string original = @"using System;
+class Foo
+{
+	private object _foo;
+
+	public void Test()
+	{
+		lock(_foo) { }
+	}
+}
+";
+			const string expected = @"using System;
+class Foo
+{
+	private readonly object _foo;
+
+	public void Test()
+	{
+		lock(_foo) { }
+	}
+}
+";
+			await VerifyFix(original, expected).ConfigureAwait(false);
+		}
+
+		[TestMethod]
+		[TestCategory(TestDefinitions.UnitTests)]
+		public async Task LockObjectsMustBeReadonlyCodeFixStaticFieldAsync()
+		{
+			const string original = @"using System;
+class Foo
+{
+	static object _foo;
+
+	public void Test()
+	{
+		lock(_foo) { }
+	}
+}
+";
+			const string expected = @"using System;
+class Foo
+{
+	static readonly object _foo;
+
+	public void Test()
+	{
+		lock(_foo) { }
+	}
+}
+";
+			await VerifyFix(original, expected).ConfigureAwait(false);
+		}
+
+		[TestMethod]
+		[TestCategory(TestDefinitions.UnitTests)]
+		public async Task LockObjectsMustBeReadonlyCodeFixPrivateStaticFieldAsync()
+		{
+			const string original = @"using System;
+class Foo
+{
+	private static object _foo;
+
+	public void Test()
+	{
+		lock(_foo) { }
+	}
+}
+";
+			const string expected = @"using System;
+class Foo
+{
+	private static readonly object _foo;
+
+	public void Test()
+	{
+		lock(_foo) { }
+	}
+}
+";
+			await VerifyFix(original, expected).ConfigureAwait(false);
+		}
+
+		[TestMethod]
+		[TestCategory(TestDefinitions.UnitTests)]
+		public async Task LockObjectsMustBeReadonlyCodeFixAlreadyReadonlyAsync()
+		{
+			const string code = @"using System;
+class Foo
+{
+	private readonly object _foo;
+
+	public void Test()
+	{
+		lock(_foo) { }
+	}
+}
+";
+			await VerifySuccessfulCompilation(code).ConfigureAwait(false);
+		}
 	}
 }