[semanticcpg] Add better exception for .method on annotations. (#5762)

* [semanticcpg] Add better exception for `.method` on annotations.

* Add `methodOption` step for Annotation and AnnotationLiteral nodes.

This step is now referenced in `method` step on CFG nodes exception.

Author: ml86

semanticcpg/src/main/scala/io/shiftleft/semanticcpg/language/nodemethods/AnnotationLiteralNodeMethods.scala

@@ -0,0 +1,11 @@
+package io.shiftleft.semanticcpg.language.nodemethods
+
+import io.shiftleft.codepropertygraph.generated.nodes.{AnnotationLiteral, Method}
+import io.shiftleft.semanticcpg.NodeExtension
+import io.shiftleft.semanticcpg.language.*
+
+class AnnotationLiteralNodeMethods(val node: AnnotationLiteral) extends AnyVal with NodeExtension {
+  def methodOption: Option[Method] = {
+    node.inAst.collectAll[Method].headOption
+  }
+}

semanticcpg/src/main/scala/io/shiftleft/semanticcpg/language/nodemethods/AnnotationNodeMethods.scala

@@ -0,0 +1,11 @@
+package io.shiftleft.semanticcpg.language.nodemethods
+
+import io.shiftleft.codepropertygraph.generated.nodes.{Annotation, Method}
+import io.shiftleft.semanticcpg.NodeExtension
+import io.shiftleft.semanticcpg.language.*
+
+class AnnotationNodeMethods(val node: Annotation) extends AnyVal with NodeExtension {
+  def methodOption: Option[Method] = {
+    node.inAst.collectAll[Method].headOption
+  }
+}

semanticcpg/src/main/scala/io/shiftleft/semanticcpg/language/nodemethods/CfgNodeMethods.scala

@@ -106,8 +106,20 @@ class CfgNodeMethods(val node: CfgNode) extends AnyVal with NodeExtension {
     case _: MethodParameterIn | _: MethodParameterOut | _: MethodReturn =>
       walkUpAst(node)
     case _: CallRepr if !node.isInstanceOf[Call] => walkUpAst(node)
-    case _: Annotation | _: AnnotationLiteral    => node.inAst.collectAll[Method].head
-    case _: Expression | _: JumpTarget           => walkUpContains(node)
+    case _: Annotation | _: AnnotationLiteral =>
+      node.inAst.collectAll[Method].headOption match {
+        case Some(method) =>
+          method
+        case _ =>
+          throw new RuntimeException(s"""|This method cannot be used on ANNOTATION or ANNOTATION_LITERAL nodes as they
+                                         |do not necessarily belong to a METHOD. This problem is caused by annotations
+                                         |invalidly implementing the CFG trait which we sadly cannot easily fix.
+                                         |As workaround you can use the `methodOption` extension on the annotation
+                                         |nodes, manually walk the AST or test a CONTAINS edge expansion to check if 
+                                         |an annotation is part of a method or not.
+                                         |""".stripMargin)
+      }
+    case _: Expression | _: JumpTarget => walkUpContains(node)
   }
 
   /** Obtain hexadecimal string representation of lineNumber field.

semanticcpg/src/main/scala/io/shiftleft/semanticcpg/language/package.scala

@@ -293,6 +293,10 @@ trait LowPrioImplicits {
   implicit def iterOnceToAstNodeDot[A <: AstNode](a: IterableOnce[A]): AstNodeDot[A] =
     new AstNodeDot(a.iterator)
 
+  implicit def toAnnotationNodeMethods(node: Annotation): AnnotationNodeMethods = new AnnotationNodeMethods(node)
+  implicit def toAnnotationLiteralNodeMethods(node: AnnotationLiteral): AnnotationLiteralNodeMethods =
+    new AnnotationLiteralNodeMethods(node)
+
   implicit def toCfgNodeMethods(node: CfgNode): CfgNodeMethods = new CfgNodeMethods(node)
 
   implicit def iterOnceToCfgNodeTraversal[A <: CfgNode](a: IterableOnce[A]): CfgNodeTraversal[A] =