Python: Add dataflow consistency query

Author: RasmusWL

python/ql/consistency-queries/dataflow-consistency.ql

@@ -0,0 +1,44 @@
+import python
+import semmle.python.dataflow.new.DataFlow::DataFlow
+import semmle.python.dataflow.new.internal.DataFlowPrivate
+import semmle.python.dataflow.new.internal.DataFlowImplConsistency::Consistency
+
+private class MyConsistencyConfiguration extends ConsistencyConfiguration {
+  override predicate argHasPostUpdateExclude(ArgumentNode n) {
+    exists(ArgumentPosition apos | n.argumentOf(_, apos) and apos.isStarArgs(_))
+    or
+    exists(ArgumentPosition apos | n.argumentOf(_, apos) and apos.isDictSplat())
+  }
+
+  override predicate reverseReadExclude(Node n) {
+    // since `self`/`cls` parameters can be marked as implicit argument to `super()`,
+    // they will have PostUpdateNodes. We have a read-step from the synthetic `**kwargs`
+    // parameter, but dataflow-consistency queries should _not_ complain about there not
+    // being a post-update node for the synthetic `**kwargs` parameter.
+    n instanceof SynthDictSplatParameterNode
+  }
+
+  override predicate uniqueParameterNodePositionExclude(
+    DataFlowCallable c, ParameterPosition pos, Node p
+  ) {
+    // For normal parameters that can both be passed as positional arguments or keyword
+    // arguments, we currently have parameter positions for both cases..
+    //
+    // TODO: Figure out how bad breaking this consistency check is
+    exists(Function func, Parameter param |
+      c.getScope() = func and
+      p = parameterNode(param) and
+      c.getParameter(pos) = p and
+      param = func.getArg(_) and
+      param = func.getArgByName(_)
+    )
+  }
+
+  override predicate uniqueCallEnclosingCallableExclude(DataFlowCall call) {
+    not exists(call.getLocation().getFile().getRelativePath())
+  }
+
+  override predicate identityLocalStepExclude(Node n) {
+    not exists(n.getLocation().getFile().getRelativePath())
+  }
+}