Python: subscript on API::Node

Author: yoff

python/ql/lib/semmle/python/ApiGraphs.qll

@@ -243,6 +243,11 @@ module API {
      */
     Node getAwaited() { result = this.getASuccessor(Label::await()) }
 
+    /**
+     * Gets a node representing a subscript of this node.
+     */
+    Node getASubscript() { result = this.getASuccessor(Label::subscript()) }
+
     /**
      * Gets a string representation of the lexicographically least among all shortest access paths
      * from the root to this node.
@@ -750,6 +755,10 @@ module API {
         lbl = Label::await() and
         ref = pred.getAnAwaited()
         or
+        // Subscripting a node that is a use of `base`
+        lbl = Label::subscript() and
+        ref = pred.getASubscript()
+        or
         // Subclassing a node
         lbl = Label::subclass() and
         exists(PY::ClassExpr clsExpr, DataFlow::Node superclass | pred.flowsTo(superclass) |
@@ -982,6 +991,7 @@ module API {
         MkLabelReturn() or
         MkLabelSubclass() or
         MkLabelAwait() or
+        MkLabelSubscript() or
         MkLabelEntryPoint(EntryPoint ep)
 
       /** A label for a module. */
@@ -1057,6 +1067,11 @@ module API {
         override string toString() { result = "getAwaited()" }
       }
 
+      /** A label that gets the subscript of a sequence. */
+      class LabelSubscript extends ApiLabel, MkLabelSubscript {
+        override string toString() { result = "getSubscript()" }
+      }
+
       /** A label for entry points. */
       class LabelEntryPoint extends ApiLabel, MkLabelEntryPoint {
         private EntryPoint entry;
@@ -1102,6 +1117,9 @@ module API {
     /** Gets the `await` edge label. */
     LabelAwait await() { any() }
 
+    /** Gets the `subscript` edge label. */
+    LabelSubscript subscript() { any() }
+
     /** Gets the label going from the root node to the nodes associated with the given entry point. */
     LabelEntryPoint entryPoint(EntryPoint ep) { result = MkLabelEntryPoint(ep) }
   }