Add File as a CFG root to support file-level declarations

Agent-Logs-Url: https://github.com/github/codeql/sessions/2867f173-c3f1-4564-9885-3ff4517bbf30

Co-authored-by: owen-mc <62447351+owen-mc@users.noreply.github.com>

Author: Copilot

go/ql/lib/semmle/go/controlflow/ControlFlowGraph.qll

@@ -9,17 +9,26 @@ private import ControlFlowGraphShared
 
 /** Provides helper predicates for mapping between CFG nodes and the AST. */
 module ControlFlow {
-  /** A function with which a CFG is associated. */
+  /** A file or function with which a CFG is associated. */
   class Root extends AstNode {
-    Root() { exists(this.(FuncDef).getBody()) }
+    Root() {
+      exists(this.(FuncDef).getBody())
+      or
+      exists(this.(File).getADecl())
+    }
 
-    /** Holds if `nd` belongs to this function. */
-    predicate isRootOf(AstNode nd) { this = nd.getEnclosingFunction() }
+    /** Holds if `nd` belongs to this file or function. */
+    predicate isRootOf(AstNode nd) {
+      this = nd.getEnclosingFunction()
+      or
+      not exists(nd.getEnclosingFunction()) and
+      this = nd.getFile()
+    }
 
-    /** Gets the synthetic entry node of the CFG for this function. */
+    /** Gets the synthetic entry node of the CFG for this file or function. */
     EntryNode getEntryNode() { result = ControlFlow::entryNode(this) }
 
-    /** Gets the synthetic exit node of the CFG for this function. */
+    /** Gets the synthetic exit node of the CFG for this file or function. */
     ExitNode getExitNode() { result = ControlFlow::exitNode(this) }
   }
 

go/ql/lib/semmle/go/controlflow/ControlFlowGraphShared.qll

@@ -63,7 +63,11 @@ module GoCfg {
     }
 
     class Callable extends AstNode {
-      Callable() { exists(this.(Go::FuncDef).getBody()) }
+      Callable() {
+        exists(this.(Go::FuncDef).getBody())
+        or
+        exists(this.(Go::File).getADecl())
+      }
     }
 
     AstNode callableGetBody(Callable c) { result = c }
@@ -72,6 +76,11 @@ module GoCfg {
       result = node and node instanceof Callable
       or
       not node instanceof Callable and result = node.getEnclosingFunction()
+      or
+      not node instanceof Callable and
+      not exists(node.getEnclosingFunction()) and
+      result = node.getFile() and
+      result instanceof Callable
     }
 
     class Stmt = Go::Stmt;