Python: Add implementation note about why not targeting ESSA node

RasmusWL · RasmusWL · commit a1225674ee41 · 2023-07-11T11:32:26.000+02:00
diff --git a/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll b/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPrivate.qll
@@ -468,6 +468,7 @@ predicate runtimeJumpStep(Node nodeFrom, Node nodeTo) {
   // function, while the default value itself will be in the scope that _defines_ the
   // function.
   exists(ParameterDefinition param |
+    // note: we go to the _control-flow node_ of the parameter, and not the ESSA node of the parameter, since for type-tracking, the ESSA node is not a LocalSourceNode, so we would get in trouble.
     nodeFrom.asCfgNode() = param.getDefault() and
     nodeTo.asCfgNode() = param.getDefiningNode()
   )

Original file line number	Diff line number	Diff line change
`@@ -468,6 +468,7 @@ predicate runtimeJumpStep(Node nodeFrom, Node nodeTo) {`
`468`	`468`	`// function, while the default value itself will be in the scope that _defines_ the`
`469`	`469`	`// function.`
`470`	`470`	`exists(ParameterDefinition param \|`
	`471`	`+ // note: we go to the _control-flow node_ of the parameter, and not the ESSA node of the parameter, since for type-tracking, the ESSA node is not a LocalSourceNode, so we would get in trouble.`
`471`	`472`	`nodeFrom.asCfgNode() = param.getDefault() and`
`472`	`473`	`nodeTo.asCfgNode() = param.getDefiningNode()`
`473`	`474`	`)`