Fix S1144 FN: Unused private getters and private setters (#9098)

analyzers/its/expected/CSharpLatest/S1144-CSharpLatest-net8.0.json

@@ -264,6 +264,12 @@
       "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/CSharpLatest/CSharpLatest/CSharp9Features/S4015.cs#L12",
       "Location": "Line 12 Position 20-28"
     },
+    {
+      "Id": "S1144",
+      "Message": "Remove the unused private setter \u0027set_Property\u0027.",
+      "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/CSharpLatest/CSharpLatest/CSharp9Features/S4015.cs#L12",
+      "Location": "Line 12 Position 36-49"
+    },
     {
       "Id": "S1144",
       "Message": "Remove the unused private property \u0027Property\u0027.",

analyzers/its/expected/akka.net/S1144-Akka-netstandard2.0.json

@@ -1,5 +1,11 @@
 {
   "Issues": [
+    {
+      "Id": "S1144",
+      "Message": "Remove the unused private setter \u0027set_TypeName\u0027.",
+      "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/akka.net/src/core/Akka/Actor/Props.cs#L229",
+      "Location": "Line 229 Position 13-61"
+    },
     {
       "Id": "S1144",
       "Message": "Remove the unused private class \u0027FactoryConsumer\u0027.",
@@ -60,6 +66,18 @@
       "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/akka.net/src/core/Akka/Helios.Concurrency.DedicatedThreadPool.cs#L569",
       "Location": "Line 569 Position 13-58"
     },
+    {
+      "Id": "S1144",
+      "Message": "Remove the unused private setter \u0027set_ExceptionHandler\u0027.",
+      "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/akka.net/src/core/Akka/Helios.Concurrency.DedicatedThreadPool.cs#L88",
+      "Location": "Line 88 Position 58-70"
+    },
+    {
+      "Id": "S1144",
+      "Message": "Remove the unused private setter \u0027set_ThreadMaxStackSize\u0027.",
+      "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/akka.net/src/core/Akka/Helios.Concurrency.DedicatedThreadPool.cs#L93",
+      "Location": "Line 93 Position 46-58"
+    },
     {
       "Id": "S1144",
       "Message": "Remove the unused private property \u0027TotalBufferSize\u0027.",

analyzers/its/expected/akka.net/S1144-Akka.Cluster-netstandard2.0.json

@@ -1,5 +1,11 @@
 {
   "Issues": [
+    {
+      "Id": "S1144",
+      "Message": "Remove the unused private setter \u0027set_Log\u0027.",
+      "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/akka.net/src/core/Akka.Cluster/AutoDown.cs#L270",
+      "Location": "Line 270 Position 43-55"
+    },
     {
       "Id": "S1144",
       "Message": "Remove the unused private field \u0027_log\u0027.",

analyzers/its/expected/akka.net/S1144-Akka.MultiNodeTestRunner-net471.json

@@ -1,5 +1,11 @@
 {
   "Issues": [
+    {
+      "Id": "S1144",
+      "Message": "Remove the unused private setter \u0027set_NextSink\u0027.",
+      "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/akka.net/src/core/Akka.MultiNodeTestRunner/Discovery.cs#L39",
+      "Location": "Line 39 Position 45-57"
+    },
     {
       "Id": "S1144",
       "Message": "Remove the unused private field \u0027_validNetCorePlatform\u0027.",

analyzers/its/expected/akka.net/S1144-Akka.MultiNodeTestRunner-net5.0.json

@@ -1,5 +1,11 @@
 {
   "Issues": [
+    {
+      "Id": "S1144",
+      "Message": "Remove the unused private setter \u0027set_NextSink\u0027.",
+      "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/akka.net/src/core/Akka.MultiNodeTestRunner/Discovery.cs#L39",
+      "Location": "Line 39 Position 45-57"
+    },
     {
       "Id": "S1144",
       "Message": "Remove the unused private method \u0027ChangeDllPathPlatform\u0027.",

analyzers/its/expected/akka.net/S1144-Akka.MultiNodeTestRunner-netcoreapp3.1.json

@@ -1,5 +1,11 @@
 {
   "Issues": [
+    {
+      "Id": "S1144",
+      "Message": "Remove the unused private setter \u0027set_NextSink\u0027.",
+      "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/akka.net/src/core/Akka.MultiNodeTestRunner/Discovery.cs#L39",
+      "Location": "Line 39 Position 45-57"
+    },
     {
       "Id": "S1144",
       "Message": "Remove the unused private method \u0027ChangeDllPathPlatform\u0027.",

analyzers/its/expected/akka.net/S1144-Akka.MultiNodeTestRunner.Shared-netstandard2.0.json

@@ -0,0 +1,10 @@
+{
+  "Issues": [
+    {
+      "Id": "S1144",
+      "Message": "Remove the unused private setter \u0027set_TestRunCompleted\u0027.",
+      "Uri": "https://github.com/SonarSource/sonar-dotnet/blob/master/analyzers/its/Projects/akka.net/src/core/Akka.MultiNodeTestRunner.Shared/Reporting/TestRunCoordinator.cs#L80",
+      "Location": "Line 80 Position 53-65"
+    }
+  ]
+}

analyzers/src/SonarAnalyzer.CSharp/Helpers/CSharpSymbolUsageCollector.cs

@@ -51,8 +51,8 @@ private enum SymbolAccess
 
         public ISet<ISymbol> UsedSymbols { get; } = new HashSet<ISymbol>();
         public IDictionary<ISymbol, SymbolUsage> FieldSymbolUsages { get; } = new Dictionary<ISymbol, SymbolUsage>();
-        public HashSet<string> DebuggerDisplayValues { get; } = new();
-        public Dictionary<IPropertySymbol, AccessorAccess> PropertyAccess { get; } = new();
+        public HashSet<string> DebuggerDisplayValues { get; } = [];
+        public Dictionary<IPropertySymbol, AccessorAccess> PropertyAccess { get; } = [];
 
         public CSharpSymbolUsageCollector(Compilation compilation, IEnumerable<ISymbol> knownSymbols)
         {

analyzers/src/SonarAnalyzer.CSharp/Rules/UnusedPrivateMember.cs

@@ -84,7 +84,7 @@ private static void NamedSymbolAction(SonarSymbolReportingContext context, HashS
             var fieldLikeSymbols = new BidirectionalDictionary<ISymbol, SyntaxNode>();
             if (GatherSymbols(namedType, context.Compilation, privateSymbols, removableInternalTypes, fieldLikeSymbols, context)
                 && privateSymbols.Any()
-                && new CSharpSymbolUsageCollector(context.Compilation, privateSymbols) is var usageCollector
+                && new CSharpSymbolUsageCollector(context.Compilation, AssociatedSymbols(privateSymbols)) is var usageCollector
                 && VisitDeclaringReferences(namedType, usageCollector, context, includeGeneratedFile: true))
             {
                 foreach (var diagnostic in DiagnosticsForUnusedPrivateMembers(usageCollector, privateSymbols, SyntaxConstants.Private, fieldLikeSymbols))
@@ -98,6 +98,9 @@ private static void NamedSymbolAction(SonarSymbolReportingContext context, HashS
             }
         }
 
+        private static IEnumerable<ISymbol> AssociatedSymbols(IEnumerable<ISymbol> privateSymbols) =>
+            privateSymbols.Select(x => x is IMethodSymbol { AssociatedSymbol: IPropertySymbol property } ? property : x);
+
         private static bool GatherSymbols(INamedTypeSymbol namedType,
                                           Compilation compilation,
                                           HashSet<ISymbol> privateSymbols,
@@ -174,12 +177,19 @@ private static IEnumerable<Diagnostic> DiagnosticsForUsedButUnreadFields(CSharpS
         private static HashSet<ISymbol> GetUnusedSymbols(CSharpSymbolUsageCollector usageCollector, IEnumerable<ISymbol> removableSymbols) =>
             removableSymbols
                 .Except(usageCollector.UsedSymbols)
-                .Where(symbol => !IsMentionedInDebuggerDisplay(symbol, usageCollector))
+                .Where(symbol => !IsMentionedInDebuggerDisplay(symbol, usageCollector) && !IsAccessorUsed(symbol, usageCollector))
                 .ToHashSet();
 
         private static IEnumerable<Diagnostic> GetDiagnosticsForUnreadFields(IEnumerable<SymbolUsage> unreadFields) =>
             unreadFields.Select(usage => Diagnostic.Create(RuleS4487, usage.Declaration.GetLocation(), GetFieldAccessibilityForMessage(usage.Symbol), usage.Symbol.Name));
 
+        private static bool IsAccessorUsed(ISymbol symbol, CSharpSymbolUsageCollector usageCollector) =>
+            symbol is IMethodSymbol { } accessor
+                && accessor.AssociatedSymbol is IPropertySymbol { } property
+                && usageCollector.PropertyAccess.TryGetValue(property, out var access)
+                && ((access.HasFlag(AccessorAccess.Get) && accessor.MethodKind == MethodKind.PropertyGet)
+                    || (access.HasFlag(AccessorAccess.Set) && accessor.MethodKind == MethodKind.PropertySet));
+
         private static string GetFieldAccessibilityForMessage(ISymbol symbol) =>
             symbol.DeclaredAccessibility == Accessibility.Private ? SyntaxConstants.Private : "private class";
 
@@ -314,9 +324,9 @@ private sealed class CSharpRemovableSymbolWalker : SafeCSharpSyntaxWalker
             private readonly Func<SyntaxNode, SemanticModel> getSemanticModel;
             private readonly Accessibility containingTypeAccessibility;
 
-            public Dictionary<ISymbol, SyntaxNode> FieldLikeSymbols { get; } = new();
-            public HashSet<ISymbol> InternalSymbols { get; } = new();
-            public HashSet<ISymbol> PrivateSymbols { get; } = new();
+            public Dictionary<ISymbol, SyntaxNode> FieldLikeSymbols { get; } = [];
+            public HashSet<ISymbol> InternalSymbols { get; } = [];
+            public HashSet<ISymbol> PrivateSymbols { get; } = [];
 
             public CSharpRemovableSymbolWalker(Func<SyntaxTree, bool, SemanticModel> getSemanticModel, Accessibility containingTypeAccessibility)
             {
@@ -430,6 +440,16 @@ public override void VisitMethodDeclaration(MethodDeclarationSyntax node)
                 base.VisitMethodDeclaration(node);
             }
 
+            public override void VisitAccessorDeclaration(AccessorDeclarationSyntax node)
+            {
+                if (node.Modifiers.Any(SyntaxKind.PrivateKeyword))
+                {
+                    ConditionalStore(GetDeclaredSymbol(node), IsRemovable);
+                }
+
+                base.VisitAccessorDeclaration(node);
+            }
+
             public override void VisitPropertyDeclaration(PropertyDeclarationSyntax node)
             {
                 if (IsPrivateOrInPrivateType(node.Modifiers))

analyzers/tests/SonarAnalyzer.Test/Rules/UnusedPrivateMemberTest.Properties.cs

@@ -136,6 +136,60 @@ public void Method3()
 
     private int Property12 { get; set; } = 42; // FN
 }
+").Verify();
+
+        [TestMethod]
+        public void UnusedPrivateMember_Properties_Accessors() =>
+            builder.AddSnippet(@"
+using System;
+public class PropertyUsages
+{
+    public int AProperty { private get; set; } // Noncompliant {{Remove the unused private getter 'get_AProperty'.}}
+    public int BProperty { get; private set; } // Noncompliant {{Remove the unused private setter 'set_BProperty'.}}
+    public int CProperty { internal get; set; } // Compliant
+    public int DProperty { get; internal set; } // Compliant
+    public int EProperty { protected get; set; } // Compliant
+    public int E2Property { get; protected set; } // Compliant
+    public int FProperty { get; private set; } // Compliant
+    public int GProperty { private get; set; } // Noncompliant {{Remove the unused private getter 'get_GProperty'.}}
+    public int HProperty { get; private set; } // Noncompliant {{Remove the unused private setter 'set_HProperty'.}}
+    public int IProperty { private get; set; } // Compliant
+    public int JProperty { get; private set; } // Compliant: both read and write
+    public int KProperty { private get; set; } // Compliant: both read and write
+    public int LProperty { get; private set; } // FN: private set is used in the constructor, not necessary
+    protected int MProperty { private get; set; } // Noncompliant {{Remove the unused private getter 'get_MProperty'.}}
+
+    public PropertyUsages()
+    {
+        LProperty = 42;
+    }
+
+    public void Method()
+    {
+        FProperty = HProperty;
+        GProperty = IProperty;
+
+        JProperty = KProperty;
+        KProperty = JProperty;
+    }
+
+    public interface ISomeInterface
+    {
+        string Something { get; }
+        string SomethingElse { get; }
+    }
+
+    public class SomeClass : ISomeInterface
+    {
+        public string Something { get; private set; } // Compliant
+        public string SomethingElse { get; private set; } // Noncompliant
+
+        public void Method(string str)
+        {
+            Something = str;
+        }
+    }
+}
 ").Verify();
     }
 }

analyzers/tests/SonarAnalyzer.Test/TestCases/UnusedPrivateMember.CSharp7.cs

@@ -201,10 +201,10 @@ private enum Y
 // https://github.com/SonarSource/sonar-dotnet/issues/6724
 public class Repro_6724
 {
-    public int PrivateGetter { private get; set; } // FN
-    public int PrivateSetter { get; private set; } // FN
+    public int PrivateGetter { private get; set; } // Noncompliant
+    public int PrivateSetter { get; private set; } // Noncompliant
 
-    public int ExpressionBodiedPropertyWithPrivateGetter { private get => 1; set => _ = value; } // FN
-    public int ExpressionBodiedPropertyWithPrivateSetter { get => 1; private set => _ = value; } // FN
+    public int ExpressionBodiedPropertyWithPrivateGetter { private get => 1; set => _ = value; } // Noncompliant
+    public int ExpressionBodiedPropertyWithPrivateSetter { get => 1; private set => _ = value; } // Noncompliant
 }
 

analyzers/tests/SonarAnalyzer.Test/TestCases/UnusedPrivateMember.Fixed.Batch.cs

@@ -176,12 +176,12 @@ public class PropertyAccess
     private int OnlyRead { get; }                                              // Fixed
     private int OnlySet { get; set; }
     private int OnlySet2 { set { } }                             // Fixed
-    public int PrivateGetter { private get; set; }                                  // FN - unused private getter
-    public int PrivateSetter { get; private set; }                                  // FN - unused private setter
+    public int PrivateGetter { set; }                                  // Fixed
+    public int PrivateSetter { get; }                                  // Fixed
     private int ExpressionBodiedProperty5 { set => _ = value; }           // Fixed
     private int ExpressionBodiedProperty6 { get => 1; }           // Fixed
-    public int ExpressionBodiedProperty7 { private get => 1; set => _ = value; }    // FN - unused private getter
-    public int ExpressionBodiedProperty8 { get => 1; private set => _ = value; }    // FN - unused private setter
+    public int ExpressionBodiedProperty7 { set => _ = value; }    // Fixed
+    public int ExpressionBodiedProperty8 { get => 1; }    // Fixed
 
     private int BothAccessed { get; set; }
 

analyzers/tests/SonarAnalyzer.Test/TestCases/UnusedPrivateMember.Fixed.cs

@@ -160,12 +160,12 @@ public class PropertyAccess
     private int OnlyRead { get; }                                              // Fixed
     private int OnlySet { get; set; }
     private int OnlySet2 { set { } }                             // Fixed
-    public int PrivateGetter { private get; set; }                                  // FN - unused private getter
-    public int PrivateSetter { get; private set; }                                  // FN - unused private setter
+    public int PrivateGetter { set; }                                  // Fixed
+    public int PrivateSetter { get; }                                  // Fixed
     private int ExpressionBodiedProperty5 { set => _ = value; }           // Fixed
     private int ExpressionBodiedProperty6 { get => 1; }           // Fixed
-    public int ExpressionBodiedProperty7 { private get => 1; set => _ = value; }    // FN - unused private getter
-    public int ExpressionBodiedProperty8 { get => 1; private set => _ = value; }    // FN - unused private setter
+    public int ExpressionBodiedProperty7 { set => _ = value; }    // Fixed
+    public int ExpressionBodiedProperty8 { get => 1; }    // Fixed
 
     private int BothAccessed { get; set; }
 

analyzers/tests/SonarAnalyzer.Test/TestCases/UnusedPrivateMember.cs

@@ -241,9 +241,10 @@ public class PropertyAccess
 //                         ^^^
     private int NotAccessed { get; set; }                                           // Noncompliant {{Remove the unused private property 'NotAccessed'.}}
 //              ^^^^^^^^^^^
-    public int PrivateGetter { private get; set; }                                  // FN - unused private getter
-    public int PrivateSetter { get; private set; }                                  // FN - unused private setter
-
+    public int PrivateGetter { private get; set; }                                  // Noncompliant {{Remove the unused private getter 'get_PrivateGetter'.}}
+//                             ^^^^^^^^^^^^
+    public int PrivateSetter { get; private set; }                                  // Noncompliant {{Remove the unused private setter 'set_PrivateSetter'.}}
+//                                  ^^^^^^^^^^^^
     private int ExpressionBodiedProperty => 1;                                      // Noncompliant {{Remove the unused private property 'ExpressionBodiedProperty'.}}
 //              ^^^^^^^^^^^^^^^^^^^^^^^^
     private int ExpressionBodiedProperty2 { get => 1; }                             // Noncompliant
@@ -253,8 +254,8 @@ public class PropertyAccess
 //                                          ^^^
     private int ExpressionBodiedProperty6 { get => 1; set => _ = value; }           // Noncompliant
 //                                                    ^^^
-    public int ExpressionBodiedProperty7 { private get => 1; set => _ = value; }    // FN - unused private getter
-    public int ExpressionBodiedProperty8 { get => 1; private set => _ = value; }    // FN - unused private setter
+    public int ExpressionBodiedProperty7 { private get => 1; set => _ = value; }    // Noncompliant
+    public int ExpressionBodiedProperty8 { get => 1; private set => _ = value; }    // Noncompliant
 
     private int BothAccessed { get; set; }