Python: Refactor SaxParserSetFeatureCall

Originally made by @erik-krogh in
https://github.com/github/codeql/pull/8693/files#diff-9627c1fb9a1cc77fb93e6b7e31af1a4fa908f2a60362cfb34377d24debb97398

Could not be applied directly to this PR, since this PR deletes the file.

Author: RasmusWL

python/ql/lib/semmle/python/frameworks/Stdlib.qll

@@ -3408,7 +3408,7 @@ private module StdlibPrivate {
    *
    * See https://docs.python.org/3.10/library/xml.sax.reader.html#xml.sax.xmlreader.XMLReader.setFeature
    */
-  private class SaxParserSetFeatureCall extends DataFlow::MethodCallNode {
+  private class SaxParserSetFeatureCall extends API::CallNode, DataFlow::MethodCallNode {
     SaxParserSetFeatureCall() {
       this =
         API::moduleImport("xml")
@@ -3421,27 +3421,9 @@ private module StdlibPrivate {
 
     // The keyword argument names does not match documentation. I checked (with Python
     // 3.9.5) that the names used here actually works.
-    DataFlow::Node getFeatureArg() { result in [this.getArg(0), this.getArgByName("name")] }
+    API::Node getFeatureArg() { result = this.getParameter(0, "name") }
 
-    DataFlow::Node getStateArg() { result in [this.getArg(1), this.getArgByName("state")] }
-  }
-
-  /** Gets a back-reference to the `setFeature` state argument `arg`. */
-  private DataFlow::TypeTrackingNode saxParserSetFeatureStateArgBacktracker(
-    DataFlow::TypeBackTracker t, DataFlow::Node arg
-  ) {
-    t.start() and
-    arg = any(SaxParserSetFeatureCall c).getStateArg() and
-    result = arg.getALocalSource()
-    or
-    exists(DataFlow::TypeBackTracker t2 |
-      result = saxParserSetFeatureStateArgBacktracker(t2, arg).backtrack(t2, t)
-    )
-  }
-
-  /** Gets a back-reference to the `setFeature` state argument `arg`. */
-  DataFlow::LocalSourceNode saxParserSetFeatureStateArgBacktracker(DataFlow::Node arg) {
-    result = saxParserSetFeatureStateArgBacktracker(DataFlow::TypeBackTracker::end(), arg)
+    API::Node getStateArg() { result = this.getParameter(1, "state") }
   }
 
   /**
@@ -3452,16 +3434,13 @@ private module StdlibPrivate {
   private DataFlow::Node saxParserWithFeatureExternalGesTurnedOn(DataFlow::TypeTracker t) {
     t.start() and
     exists(SaxParserSetFeatureCall call |
-      call.getFeatureArg() =
+      call.getFeatureArg().getARhs() =
         API::moduleImport("xml")
             .getMember("sax")
             .getMember("handler")
             .getMember("feature_external_ges")
             .getAUse() and
-      saxParserSetFeatureStateArgBacktracker(call.getStateArg())
-          .asExpr()
-          .(BooleanLiteral)
-          .booleanValue() = true and
+      call.getStateArg().getAValueReachingRhs().asExpr().(BooleanLiteral).booleanValue() = true and
       result = call.getObject()
     )
     or
@@ -3471,16 +3450,13 @@ private module StdlibPrivate {
     // take account of that we can set the feature to False, which makes the parser safe again
     not exists(SaxParserSetFeatureCall call |
       call.getObject() = result and
-      call.getFeatureArg() =
+      call.getFeatureArg().getARhs() =
         API::moduleImport("xml")
             .getMember("sax")
             .getMember("handler")
             .getMember("feature_external_ges")
             .getAUse() and
-      saxParserSetFeatureStateArgBacktracker(call.getStateArg())
-          .asExpr()
-          .(BooleanLiteral)
-          .booleanValue() = false
+      call.getStateArg().getAValueReachingRhs().asExpr().(BooleanLiteral).booleanValue() = false
     )
   }