Python: Add getADefiningWrite

Author: tausbn

python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll

@@ -335,11 +335,7 @@ predicate runtimeJumpStep(Node nodeFrom, Node nodeTo) {
   nodeFrom = nodeTo.(ModuleVariableNode).getAWrite()
   or
   // Setting the possible values of the variable at the end of import time
-  exists(SsaVariable def |
-    def = any(SsaVariable var).getAnUltimateDefinition() and
-    def.getDefinition() = nodeFrom.asCfgNode() and
-    def.getVariable() = nodeTo.(ModuleVariableNode).getVariable()
-  )
+  nodeFrom = nodeTo.(ModuleVariableNode).getADefiningWrite()
 }
 
 /**

python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPublic.qll

@@ -393,6 +393,15 @@ class ModuleVariableNode extends Node, TModuleVariableNode {
     result.asVar().getDefinition().(EssaNodeDefinition).definedBy(var, any(DefinitionNode defn))
   }
 
+  /** Gets the possible values of the variable at the end of import time */
+  CfgNode getADefiningWrite() {
+    exists(SsaVariable def |
+      def = any(SsaVariable ssa_var).getAnUltimateDefinition() and
+      def.getDefinition() = result.asCfgNode() and
+      def.getVariable() = var
+    )
+  }
+
   override DataFlowCallable getEnclosingCallable() { result.(DataFlowModuleScope).getScope() = mod }
 
   override Location getLocation() { result = mod.getLocation() }