Fix S2225 FP: Support static virtual/abstract interface methods (#6335)

analyzers/src/SonarAnalyzer.CSharp/Facade/CSharpSyntaxFacade.cs

@@ -119,4 +119,7 @@ public override SyntaxNode RemoveParentheses(SyntaxNode node) =>
 
     public override bool TryGetGetInterpolatedTextValue(SyntaxNode node, SemanticModel semanticModel, out string interpolatedValue) =>
         Cast<InterpolatedStringExpressionSyntax>(node).TryGetGetInterpolatedTextValue(semanticModel, out interpolatedValue);
+
+    public override bool IsStatic(SyntaxNode node) =>
+        Cast<BaseMethodDeclarationSyntax>(node).IsStatic();
 }

analyzers/src/SonarAnalyzer.Common/Facade/SyntaxFacade.cs

@@ -47,6 +47,7 @@ public abstract class SyntaxFacade<TSyntaxKind>
     public abstract SyntaxNode RemoveParentheses(SyntaxNode node);
     public abstract string NodeStringTextValue(SyntaxNode node, SemanticModel semanticModel);
     public abstract bool TryGetGetInterpolatedTextValue(SyntaxNode node, SemanticModel semanticModel, out string interpolatedValue);
+    public abstract bool IsStatic(SyntaxNode node);
 
     protected static T Cast<T>(SyntaxNode node) where T : SyntaxNode =>
         node as T ?? throw new InvalidCastException($"A {node.GetType().Name} node can not be cast to a {typeof(T).Name} node.");

analyzers/src/SonarAnalyzer.Common/Rules/ToStringShouldNotReturnNullBase.cs

@@ -63,5 +63,6 @@ private bool WithinToString(SyntaxNode node) =>
         node.Ancestors()
             .TakeWhile(x => !IsLocalOrLambda(x))
             .Any(x => Language.Syntax.IsKind(x, MethodKind)
-                && nameof(ToString).Equals(Language.Syntax.NodeIdentifier(x)?.ValueText, Language.NameComparison));
+                && nameof(ToString).Equals(Language.Syntax.NodeIdentifier(x)?.ValueText, Language.NameComparison)
+                && !Language.Syntax.IsStatic(x));
 }

analyzers/src/SonarAnalyzer.VisualBasic/Extensions/MethodBlockSyntaxExtensions.cs

@@ -0,0 +1,27 @@
+/*
+ * SonarAnalyzer for .NET
+ * Copyright (C) 2015-2022 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.Extensions;
+
+public static class MethodBlockSyntaxExtensions
+{
+    public static bool IsShared(this MethodBlockSyntax methodBlock) =>
+        methodBlock.SubOrFunctionStatement.Modifiers.Any(SyntaxKind.SharedKeyword);
+}

analyzers/src/SonarAnalyzer.VisualBasic/Extensions/SyntaxNodeExtensions.cs

@@ -38,7 +38,7 @@ public static ControlFlowGraph CreateCfg(this SyntaxNode block, SemanticModel mo
 
         public static bool IsPartOfBinaryNegationOrCondition(this SyntaxNode node)
         {
-            if (!(node.Parent is MemberAccessExpressionSyntax))
+            if (node.Parent is not MemberAccessExpressionSyntax)
             {
                 return false;
             }

analyzers/src/SonarAnalyzer.VisualBasic/Facade/VisualBasicSyntaxFacade.cs

@@ -121,4 +121,7 @@ public override SyntaxNode RemoveParentheses(SyntaxNode node) =>
 
     public override bool TryGetGetInterpolatedTextValue(SyntaxNode node, SemanticModel semanticModel, out string interpolatedValue) =>
         Cast<InterpolatedStringExpressionSyntax>(node).TryGetGetInterpolatedTextValue(semanticModel, out interpolatedValue);
+
+    public override bool IsStatic(SyntaxNode node) =>
+        Cast<MethodBlockSyntax>(node).IsShared();
 }

analyzers/tests/SonarAnalyzer.UnitTest/TestCases/ToStringShouldNotReturnNull.CSharp11.cs

@@ -2,7 +2,7 @@
 {
     static virtual string ToString()
     {
-        return null; // Noncompliant FP
+        return null; // Compliant
     }
 }
 
@@ -11,10 +11,10 @@ public interface SomeOtherInterface
     static abstract string ToString();
 }
 
-public class SomeClass: SomeOtherInterface
+public class SomeClass : SomeOtherInterface
 {
     public static string ToString()
     {
-        return null; // Noncompliant FP
+        return null; // Compliant
     }
 }

analyzers/tests/SonarAnalyzer.UnitTest/TestCases/ToStringShouldNotReturnNull.cs

@@ -131,4 +131,12 @@ public override string ToString()
             return null; // Noncompliant
         }
     }
+
+    public class SomeClass
+    {
+        public static string ToString()
+        {
+            return null; // Compliant
+        }
+    }
 }

analyzers/tests/SonarAnalyzer.UnitTest/TestCases/ToStringShouldNotReturnNull.vb

@@ -63,22 +63,30 @@ Namespace Compliant
             Return String.Empty
         End Function
     End Structure
-	
-	Class ToString
-	
-		Public Function SomeMethod() As String
+
+    Class ToString
+
+        Public Function SomeMethod() As String
             Return Nothing 'Compliant
         End Function
-	
-	End Class
-	
-	Class BinaryConditionalExpressionNotSupported
-	
-		Public Function SomeMethod() As String
+
+    End Class
+
+    Class BinaryConditionalExpressionNotSupported
+
+        Public Function SomeMethod() As String
             Return If(Nothing, Nothing) ' Not supported, doesn't make sense
         End Function
-
-	End Class
+
+    End Class
+
+    Class ToStringSharedMethod
+
+        Public Shared Function ToString() As String
+            Return Nothing
+        End Function
+
+    End Class
 
 End Namespace
 
@@ -96,8 +104,8 @@ Namespace Noncompliant
     End Class
 
     Public Class ReturnsNothingConditionaly
-    
-       Public Overrides Function ToString() As String
+
+        Public Overrides Function ToString() As String
             If Condition.[When]() Then
                 Return Nothing ' Noncompliant
             End If
@@ -111,15 +119,15 @@ Namespace Noncompliant
             Return If(Condition.[When](), Nothing, "")  ' Noncompliant
         End Function
     End Class
-	
-	Public Class ReturnsNullViaNestedTenary
-    
-         Public Overrides Function ToString() As String
+
+    Public Class ReturnsNullViaNestedTenary
+
+        Public Overrides Function ToString() As String
             Return If(Condition.When(), ' Noncompliant
-				If(Condition.When(), Nothing , "something"),
-				If(Condition.When(), "something", Nothing))
-		End Function
-			 
+                If(Condition.When(), Nothing, "something"),
+                If(Condition.When(), "something", Nothing))
+        End Function
+
     End Class
 
     Structure StructReturnsNothing