C#: Exclude System.Runtime.CompilerServices attributes from XML documentation needed check

csharp/ql/src/Documentation/Documentation.qll

@@ -45,7 +45,10 @@ predicate declarationHasXmlComment(Declaration d) { exists(getADeclarationXmlCom
 /** Whether a declaration should have documentation. */
 predicate isDocumentationNeeded(Modifiable decl) {
   decl.isUnboundDeclaration() and // Exclude constructed types and methods
-  not exists(decl.(Attributable).getAnAttribute()) and // An attribute may serve to document
+  not exists(Attribute a |
+    a = decl.(Attributable).getAnAttribute() and
+    not a.getType().hasFullyQualifiedName("System.Runtime.CompilerServices", _)
+  ) and // An attribute may serve to document
   decl.isPublic() and
   (
     // The documentation of the overridden method (e.g. in an interface) is sufficient.

csharp/ql/src/change-notes/2024-08-12-doc-comments.md

@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* Attributes in the `System.Runtime.CompilerServices` namespace are ignored when checking if a declaration requires documentation comments.

csharp/ql/test/query-tests/Documentation/XmldocMissing.expected

@@ -1,3 +1,4 @@
 | documentation.cs:39:16:39:22 | method3 | Public method should be documented. |
 | documentation.cs:51:18:51:23 | Class2 | Public class should be documented. |
 | documentation.cs:74:12:74:17 | Class1 | Public constructor should be documented. |
+| documentation.cs:135:17:135:23 | method6 | Public method should be documented. |

csharp/ql/test/query-tests/Documentation/documentation.cs

@@ -123,4 +123,23 @@ class Class2 : Class1
     // GOOD: Even if the overridden method is bad.
     /// <inheritdoc/>
     public override int method4<T>(int p1, int p2) { return p1; }
+
+    // GOOD: Has an attribute
+    [My1]
+    public void method5()
+    {
+    }
+
+    // BAD: Has only System.Runtime.CompilerServices attribute
+    [System.Runtime.CompilerServices.My2]
+    public void method6()
+    {
+    }
+}
+
+internal class My1Attribute : Attribute { }
+
+namespace System.Runtime.CompilerServices
+{
+    internal class My2Attribute : Attribute { }
 }