Python: Update data-flow caching

Author: hvitved

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

@@ -228,7 +228,6 @@ module EssaFlow {
  * data flow. It is a strict subset of the `localFlowStep` predicate, as it
  * excludes SSA flow through instance fields.
  */
-cached
 predicate simpleLocalFlowStep(Node nodeFrom, Node nodeTo) {
   // If there is ESSA-flow out of a node `node`, we want flow
   // both out of `node` and any post-update node of `node`.
@@ -1559,7 +1558,6 @@ predicate kwUnpackReadStep(CfgNode nodeFrom, DictionaryElementContent c, Node no
  * any value stored inside `f` is cleared at the pre-update node associated with `x`
  * in `x.f = newValue`.
  */
-cached
 predicate clearsContent(Node n, Content c) {
   exists(CallNode call, CallableValue callable, string name |
     call_unpacks(call, _, callable, name, _) and

python/ql/src/semmle/python/dataflow/new/internal/TaintTrackingPrivate.qll

@@ -9,37 +9,43 @@ private import semmle.python.dataflow.new.internal.TaintTrackingPublic
  */
 predicate defaultTaintSanitizer(DataFlow::Node node) { none() }
 
-/**
- * Holds if the additional step from `nodeFrom` to `nodeTo` should be included in all
- * global taint flow configurations.
- */
-predicate defaultAdditionalTaintStep(DataFlow::Node nodeFrom, DataFlow::Node nodeTo) {
-  localAdditionalTaintStep(nodeFrom, nodeTo)
-  or
-  any(AdditionalTaintStep a).step(nodeFrom, nodeTo)
-}
+private module Cached {
+  /**
+   * Holds if the additional step from `nodeFrom` to `nodeTo` should be included in all
+   * global taint flow configurations.
+   */
+  cached
+  predicate defaultAdditionalTaintStep(DataFlow::Node nodeFrom, DataFlow::Node nodeTo) {
+    localAdditionalTaintStep(nodeFrom, nodeTo)
+    or
+    any(AdditionalTaintStep a).step(nodeFrom, nodeTo)
+  }
 
-/**
- * Holds if taint can flow in one local step from `nodeFrom` to `nodeTo` excluding
- * local data flow steps. That is, `nodeFrom` and `nodeTo` are likely to represent
- * different objects.
- */
-predicate localAdditionalTaintStep(DataFlow::Node nodeFrom, DataFlow::Node nodeTo) {
-  concatStep(nodeFrom, nodeTo)
-  or
-  subscriptStep(nodeFrom, nodeTo)
-  or
-  stringManipulation(nodeFrom, nodeTo)
-  or
-  containerStep(nodeFrom, nodeTo)
-  or
-  copyStep(nodeFrom, nodeTo)
-  or
-  forStep(nodeFrom, nodeTo)
-  or
-  unpackingAssignmentStep(nodeFrom, nodeTo)
+  /**
+   * Holds if taint can flow in one local step from `nodeFrom` to `nodeTo` excluding
+   * local data flow steps. That is, `nodeFrom` and `nodeTo` are likely to represent
+   * different objects.
+   */
+  cached
+  predicate localAdditionalTaintStep(DataFlow::Node nodeFrom, DataFlow::Node nodeTo) {
+    concatStep(nodeFrom, nodeTo)
+    or
+    subscriptStep(nodeFrom, nodeTo)
+    or
+    stringManipulation(nodeFrom, nodeTo)
+    or
+    containerStep(nodeFrom, nodeTo)
+    or
+    copyStep(nodeFrom, nodeTo)
+    or
+    forStep(nodeFrom, nodeTo)
+    or
+    unpackingAssignmentStep(nodeFrom, nodeTo)
+  }
 }
 
+import Cached
+
 /**
  * Holds if taint can flow from `nodeFrom` to `nodeTo` with a step related to concatenation.
  *